Length and Area

Cubic measurements
Older measures
Interesting tape measures
Rough conversion between Imperial and Metric


12 lines = 1 inch
12 inches = 1 foot
3 feet = 1 yard
1760 yards = 1 mile

36 inches = 1 yard
440 yards = quarter mile
880 yards = half mile
100 links = 1 chain
10 chains = 1 furlong
8 furlongs = 1 mile

4 inches = 1 hand
22 yards = 1 chain
5.5 yards = 1 rod, pole or perch
4 poles = 1 chain
40 poles = 1 furlong



Enter number and select unit.
Select other units for conversion.


inch in or "
foot ft or '
yard yd
mile m or mi

You can see that there might be some confusion over m (meaning miles) and m (meaning metres)!


1 furlong x 1 pole = 1 rood
40 (sq) poles = 1 rood
1210 square yards = 1 rood
1 furlong x 1 chain = 1 acre
10 square chains = 1 acre
4 roods = 1 acre
160 (sq) poles = 1 acre
4840 square yards = 1 acre
640 acres = 1 square mile



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Select other units for conversion.

Rods, poles, perches and roods were all rather confused. They could all be a measure of length (5.5 yards). Rods, poles and perches could also be a measure of area (5.5 yards square, or 30.25 square yards). So a 10 perch allotment would be 5.5 yards wide by 55 yards long. A rood could be a measure of area (1210 square yards). The dictionary also cheerfully states that this could vary round the country!

Someone researching a Enclosure map of Castle Donington dated 1779 in Nottingham local Records Office says that the entries mention areas measured in "... A, ...R, ...P". I think this must stand for Acres, Roods and Poles (or possibly Perch). There are 40 poles to the rood, and 4 roods to the acre, which seems a reasonable collection of units. A correspondent confirms this from his research of a Rate Valuation List for assessing poor law rates in the Parish of Doulting in Somerset. He found "the maximum amount under P was 37 and the maximum under R was 3." He lives in British Columbia, and went on to say "In Canada and I am sure in the USA, at least in the West, roads and highways were always dedicated (not paved!) 66 ft wide (i.e. 1 chain).  The soft metric conversion is 20 m which is almost exactly the same." (This is length rather than area, of course).

As a further complication, I have a reference to 1 perch of stone being 24 cubic feet, making it a cubic measurement!

If you want to visualise an acre, it's a square with sides 208.71 feet, or 69.7 yards.

I have been sent some old examination questions for candidates  for admittance to American High School.

Multiply 17 A, 3 R, 28 rds, 19 yds, 8 ft, 97 in, by 9

I think that A are acres, R are roods, rds are (square) rds, yds are (square) yards,ft are (square) feet and in are (square) inches. The square units are implied, else the question doesn't make sense!

Divide 45 T, 17 ewt, 1 qr, 24 lbs, 12 oz, 8 dr, by 8

Here we have tons, a misprint for hundredweight (cwt), quarters (usually abbreviated as qtr in Britain), pounds, ounces and drams. I leave the sum as an exercise for the readers!

While I am not giving metric tables (they're BORING), a hectare is 10,000 square metres (or a hundredth of a square kilometre). This is equivalent to a square 100 metres on each side. I've also been told that 1 square metre is a centiare, 100 centiares to an are, and 100 ares to a hectare. A hectare is about two and a half acres.

In the Channel Islands, a vergee is a standard measure of land, but the statutory definition differs between the bailiwicks.
In Guernsey, a vergée (Dgèrnésiais: vergie) is 17,640 square feet. It is 40 (square) Guernsey perches. A Guernsey perch (also spelt perque) is 21 feet by 21 feet.
In Jersey, a vergée (Jèrriais: vrégie) is 19,360 square feet. It is 40 (square) Jersey perches. A Jersey perch (also spelt pèrque) is 22 feet by 22 feet.
For comparison, a British perch (the area measurement) is 272.25 square feet, the Guernsey perch is 441 square feet and the Jersey perch is 484 sq feet - rather a difference!

A lovely letter in New Scientist said "The proper units for large areas, such as those of giant icebergs and hurricanes, are the Wales (metric) and the Delaware (imperial). The conversion rate is approximately 3.215 Delawares to the Wales... Measurements of height is, of course, in Eiffeltowers and Empirestatebuildings (1.368 Eiffeltowers to the Empirestatebuilding)." Here is a good website which calculates areas in this unit! I think that the Wales has replaced the Isleofwight, which used to be the standard unit. I have also spotted the Luxembourg as a measure of icebergs as well. This is, of course, rather a large area. A football pitch is often used for small areas, and Cambridge has been used for medium areas. As a very rough approximation (and that is all these units are!)

5000 Football Pitches = 1 Cambridge

500 Cambridges = 1 Wales.

Cubic Measurements

It seems logical to go onto cubic measurements or volume after talking about area. Volume is usually measured in units such as pints, gallons and so on, which are described in a separate webpage. You also have cubic inches and so on. There don't seem to be many cubic measurements similar to the acre. Here are a couple.

1 cord foot = 16 cubic feet
1 cord = 128 cubic feet
3 measured ricks = 1 cord

I thought the cord was an American unit, but a corresepondent corrected me. He said that it was used in Northumberland. "My father was using cords in his younger days when he worked in a timber yard. I remember him showing me a strange tape measure, marked with units about 4" apart, that they used to work out the cordage of a piece of timber from its length." Also, a webpage on the Common Rights in the New Forest mentions that a cord is a stack of wood in 4 foot lengths, 4 feet high and 8 feet long. It is concerned with Right of Fuelwood (Estovers).
In some districts the cord had dimensions of 16 feet by 4 feet by 2 feet. This is still 128 cubic feet.

This website claims that in England, a fathom is a measure of capacity for round wood = 216 cubic feet, that is, the volume that would be occupied by a stack 6 feet long, 6 feet wide, and 6 feet high. That is surprising, as a fathom is usually a nautical term of length meaning 6 feet (deep). The same website also claims that in Yorkshire, England, the fandam was a measure of the circumference of haystacks, measured by a circle of people hugging the stack, their outstretched hands just touching.

Another correspondent told me about the measured rick, and added "A rick is a any size stack of cornstalks, wood, straw or similar stuff, left in the field. Any ol' pile of firewood may also be called a rick, although most people just call it a woodpile. It takes about 8 cords of wood to heat a home for the entire winter."

There is a volume of measure for lumber in the US called the board-foot. A board foot is 144 cubic inches (or 1 foot x 1 foot x 1 inch). Rough lumber is sold in it. See Board Feet Estimation calculator. I have received an email about this: "My father  was a carpenter as was  father and grandfather,  and  in my youth I regularly overheard them using the  term 'super foot', which in short was 1 foot x 1 foot x  1 inch.     Prior to changing to metric measures, I  found the  term  commonly used  throughout Australia;  I  am led to believe  that it came from the UK." Has anyone from the UK heard of a similar measurement?
A correspondent answers this: "The use of super in conjunction with area measurement is short for superficial. All materials ordered from quarries whether hoggin, graded chippings or tarmac, are ordered by the yard or metre. These are cubic yards or cubic metres. Therefore a '10 yard load of tarmac' is actually 10 cubic yards. When the tarmac is spread 3" thick, the area covered is 120 super, or 120 square yards. In each case the word 'cubic' or 'square' is omitted but the words 'yard' or 'super' make the meaning absolutely clear. The Shorter Oxford English Dictionary gives one of the meanings of 'superficial' as meaning 'relating to or involving two dimensions; esp. relating to extent of surface'".
A further comment from another correspondent: "In New Zealand the super foot was the standard measure for milled timer being 144 cubic inches.  I spend many years in timber as did my father and great grand fathers.  All large quantities of timber were described in super feet which was very handy for recutting.  Stocktaking in the timber yards, sales analysis and buying was similarly calculate in super feet.  it was easy to estimate the timber in a bundle or packet by eye.  Super feet slowly died out when we officially went metric in about 1975 but as you can imagine many of the old hands still used super feet to communicate with others skilled in the measure.   The conversion from super feet to lineal feet of a board was easy.  Conversion of a metric cube to lineal feet is much slower if done on the spot mentally."

There are various other measurements for timber including "Hoppus foot" (H.ft). 1 H.ft. = 1.273 cu.ft, or 1 cu.ft. = 0.785 H.ft. The hoppus foot is used for round or rough-squared timber and the formula uses the mid-quarter-girth (M.Q.G.) in inches, squared, then multiplied by the length in feet and then divided by 144 to give H.ft. The girth is measured in inches at the mid-point between the butt and the tip and then divided by 4 to get the M.Q G. Quarter Girth tapes are available, with 66' tapes for the length, and ready-reckoner tables for standard types of timber eg. pit props.Other common timber terms were the ton for firewood and pulpwood, the bundle for stakes and pea-sticks etc., and the linear foot for pit-props and fence rails etc. Wood for chipboard or fibreboard is sometimes traded in units of 100 cu. ft. of piled chips, equivalent to 50 H.ft. of solid wood.

My father used to work in th wooden beer barrel trade (a long time ago!) He says that the staves that went to make up a barrel were counted in mille. This was 1200 staves rather than a thousand.

I have a reference to a shipping ton = 40 cubic feet. This seems odd, since ton is usually a weight. But perhaps ships are more interested in volume! However, I have subsequently been informed by my of my useful correspondents that "This measurement allows shippers to obtain revenue based on either volume or weight and is an approximate equalisation of the volume and weight rates. Rates are usually obtained by the tonne, but large and light freights are charged by volume or 'freight (or shipping) tonne'."

Referring to my statement above that "There don't seem to be many cubic measurements similar to the acre", a correspondent says "You may be interested in knowing about the 'acre-foot'. Here in the USA it is used in reference to reservoir size and is the amount of water needed to cover an acre to the depth of one foot." Very logical! Another correspondent gives from his FUI (Fund of Useless Information) "It needs 22,000 gallons of water to cover an acre of land with one inch of irrigation."

Cubic measurement is really the same as capacity or volume. However, the measurements are on this page are used for objects that have dimensions, such as wood, while capacity units, like pints and bushels, are used for liquids or dry goods that can be poured into a bag, such as grain. A bushel is 1.28 cubic feet, but we don't normally think of it like that!

Older measures

There are some measures that were not in our "tables" which we had to learn as children, because they had fallen into disuse. However, you do read about them. Many imperial measures of length were originally taken from parts of the body, sometimes obviously, such as hands or feet. But then at some time a standard length was decided on, and used by everyone. These older measurements, however, are not so precise.

Interesting tape measures

I have received some emails about old tape measures, asking me about them.
The first request says "I collect a few old tools and I have an old 50 foot tape measure in a beautifully made leather case with brass winding handle etc. It's marked in feet and inches on one side but on the reverse it's in unspecified divisions. They are 7 3/4" approx 197mm long. Any idea what they may represent? The measure is English. It has the makers name on it but they ceased trading in the 1970s.I think the measure was my Dad's. In that case I would date it mid 1950s. My Dad was a construction engineer for a company called Dexion who made steel racking systems for warehouses etc. Perhaps they had the tapes specially made and the mystery divisions were to their specifications."
From a correspondent: "I have a 50 ft tape in a leather case, on one side stamped "John Rabone & Sons, Birmingham, England", on the other side "Rabone's Metallic Wired Tape", with a brass winding handle. I believe Rabone's have ceased trading. It came to me from a shed clearance of a person who had worked for a city council. On one side of the tape it is marked in feet and inches, i.e. 1 ... 11 1ft 1 ... 11 2ft .... On the reverse is marked '1 Link ..... 2 ...... 3 ........'. Ten links is opposite 6ft 7 (.2) inches, or 10 links = 79.2 inches, 100 links = 792 inches = 66 feet = 22 yards = 1 chain. I think this sounds very similar to, if not the same as, the one in your Interesting Tape Measures section."
Another email: 'I recently bought a Chesterman leather-cased tape measure at an auction in Manhattan, Kansas. The brass winder says 100 ft. and it has the same markings on the back of the tape as described in several of your e-mails. It starts with 1 link, and has numbered marks approximately every 7 3/4" and where mark 25 would be says 1 Pole. I think this clarifies some things seen on other tape measures. I was wondering how rare these tape measures are, and when they were made.'
Some of these tapes are definitely measuring links. A link is 7.92 inches and there are 25 links to a pole. But the first tape measure is described at 7 3/4" or 197mm. A link is over 201mm, and is closer to 8" than 7 3/4". So they may not all be the same.
A suggestion from another correspondent: 'Has anyone suggested that it might be related to masonry?   The usual rule-of-thumb that I use is that a brick is nominally 8" in length and 2-2/3" in height so that 3 rows = 8".   Of course this has to include the mortar so there is a lot of opportunity to vary the relationships. Anyhow, that was my thought:   A means to quickly determine the number of bricks.'
tape tape The second says "My better half found this item laying on the shingle at Bradwell on Sea. A tiny tape measure with J.Curwel & Sons on it. It looks 19th C. but what the hell is it for measuring? As you can see the increments apparently make no logical sense...but they must! The tape has standard imperial inch divisions with tiny numbers denoting each inch. I think it would have been a yard measure as the last symbol is III... but with mysterious numbers placed at strange intervals that get closer and closer together in multiples of three, then four, then six! The numbers go from 60 - 144, but 144 is where the tape has broken so it may have continued a little further? The imperial inches go one way, the strange increments the other! I hope you can help us identify this mysterious tape measure."
I've had one suggestion for this: "This sounds like a surveyors tape and would be used for possibly works out no of degrees like an engineers protractor."
My original idea was that it measured the width of a drum, of paper or cloth or similar. As the drum got wider, the length wound round the drum would get longer per wind.
tape Another suggestion sounds distinctly interesting! "Back in my youth, early 1950s,  I was learning to play the piano.   My parents bought me a pocket metronome for Christmas.   This was the same as a measuring tape (which my brother got at the same time!) but had a non-linear scale.   If I pulled it out to the 60 marking, held it by the end and let it swing like a pendulum, it gave me a reference for 60 beats per minute.   At 120 it meant 120 beats per minute.   Follow this through and each time you halve the length, the number of beats per minute doubles - hence the non-linear markings.   My metronome had a cloth tape and the  housing was made of plastic with an internal spring and ratchet with a small button to allow the tape to be  rewound.   As I remember, the scale was from 60 upwards - because of the non-linearity, it would have been to long to be used at slower rates!   Also there was a length of tape beyond the last marking - it would not have swung for very long at short lengths.   I don't remember the exact highest rate - probably around 160.   I would guess that the tape was just over a yard when fully extended.   I've never seen one since my childhood and I don't remember what happened to  mine in the end!" (He did eventually find it - photo on the right.)  "At least my pocket metronome allowed my father's mahogany cased  French Maelzel Paquet Metronome to survive -  I inherited that!   If it was a pocket metronome, some of the Curwel tape is missing.   From my school physics, I remember a pendulum would indicate 60 beats a minute when the length from the pivot to the point of the centre of gravity of the weight on the end was approximately 39 inches.   I was taught not let it swing more than 20 - 30 degrees or it became inaccurate!" If the name is J.Curwen & Sons, they were musical publishers, so this becomes a distinct possibility. There is an article about John Curwen
I've had confirmation of this from John Ledwon who has a collection of metronomes. He says "Yes it is a very old portable metronome. You hold the end of the tape and unwind it to the speed you want and then move it to get a pendulum effect...the time for the swing is approximately what is written on the tape. I have one and it works quite well."

This was a more general query: "when u look on any tape measure every 16inches has a mark and nowhere says wot this mark means, please say if u no cos so many mates of mine are trying to work it out."
I have had a suggestion for this - " The tape measures with marks at 16" intervals.... I have seen them used for drywalling (plasterboards, partitions etc) in America etc...that is where an 8'x4' sheet is divided for fixing..i.e. every 16" for battons, hope this helps. More of a chippies tape you might say."
Another suggestion: 'The marks are put there to make it easy to set out rafters joists etc. Most board material came in increments of 4 feet ie. 8ft by 4ft plywood sheet. a joist every 16" would mean 4 supports for each board, allowing for joins.'
Someone else says that joists in America come at two foot intervals, and 16 inches is the typical spacing for wall studs used in wood-frame construction.
Enough, already! It's a tape measure used by American builders. (And in Britain we call them builders even if they work in wood.) But no, a further comment: "I agree with the suggestion that 16 inches is for drywall work.  In England the standard distance betwen uprights in a stud wall was 16 inches.  Also floor joists were usually at 16 inches if the had to carry ex 1 inch boards." So an American or British builders' tape.

chain chain This is a chain with 100 links each one foot long, making 100 feet in total. This means that is cannot be a surveyor's chain (the usual chain, which is the length of a cricket pitch). Some research on the web has found that it is a Ramsden's chain or engineer's chain. One of the strange brass tags has Chesterman Sheffield England stamped on it. There was a firm based in Sheffield called Raybone Chesterman making tools until recently. So this describes the chain, but we don't know what it was used for, or who 'Ramsden' was, or what the different shaped brass tags mean.
An email suggests that Ramsden was Jesse Ramsden (1735-1800), an English astronomical and scientific instrument maker. See Wikipedia article.
I've had another email: "When I was at college, we used surveying chains, I can't remember what length they were since we were working in metric but we had some experience on some of the older equipment. The chains had plastic tags along their length which made it easier to identify how far along the chain you were without having to count the links. Could the metal shaped tags be a similar idea with different numbers of 'teeth' instead of numbers?"
Another email about the Rabone Chesterman Land chain: "I found a set of these destined for the dump. They are new and unused and in the original damaged box. I have a Buck & Hickman 1964 catalogue which shows them. The brass tallys are 10 feet apart. The model number on the box is 558 although the catalogue has 258 as one of the 3 types."

Another email: 'I have a tape measure, that I bought at a car boot sale, it's new looking, plastic and metal. It has marks on the imperial side for 12", which is a foot, 16", which I use for stud walls for 16"centres, but the one that is puzzling me is the one at 19" 7/32nds, that is nineteen inches and seven thirty seconds, I believe it is one fifth of eight foot, but I have never come across anybody who uses this measurement. I would be very grateful if you could provide me with an answer.' Thanks for the answer I was sent, which is on this website.'The black diamond on the top scale starting at 19.2 inches is for truss layouts for 8-foot sheet goods —also referred to as the "black truss" markings. If you divide five into 96 inches (8 feet), it will give 19.2 inches —in other words, 5 trusses per sheet.'

Rabone Chesterman has been mentioned above. I was sent the following information: 'Just seen your mention of Rabone (misspelt Raybone) Chestermans on the web. I think the factory closed in 1979, although the front office block was retained and converted to new offices. I took a lot of photographs, including some of them making land-chains, and as you might imagine they had a specially long works building to check these in for accuracy. The company was an amalgamation of a works called Chestermans in Sheffield and Rabones in Birmingham, dating back to the 1700s. I managed to salvage a few large brass and steel templates used for taking off measurements (using a pantograph process) to etch into steel rulers (a lot were going for scrap as the works was closing). The staff were all very proud of the company and there was a real feeling of sadness at the closure and the loss of two hundred years of history. I think the trade name was bought by Stanley Tools.'

More about Chesterman: "Here's one of the Chesterman template rulers. 343 is the pattern number, and the engraved woring says 'standard for taper nedge (sic), 64ths, 1/64 to 9/64ths'. Someone with just as bad spelling has penned a newer number 828 and 'revers side' on! All this is engraved onto the back of a recycled 2" wide steel ruler. Rabone's are still making steel rules, but everything moved back to Birmingham when the factory closed. I'm not sure exactly what Stanley Tools purchased, maybe the flexible steel measuring tape side of the business."

If anyone else knows anything about any of these tapes or measures, please contact me and I'll pass the information on.

Rough conversion between Imperial and Metric

I find many Imperial to Metric conversions very irritating, because they are far too precise. So here are some rough conversions which you can carry in your head.

Five centimetres is just less than two inches.

Five millimetres is just less than a fifth of an inch.

A foot is slightly more than 30 centimetres (think of a ruler).

A metre is a few inches more than a yard.

A kilometre is over half a mile (about 5/8 if you don't mind fractions).

A hectare is about two and a half acres.

Beware something called a metric foot, used by DIY stores. It is 30 centimetres long, which is less than a foot, and you don't get a whole number of them to a metre. So it is useless for both imperial and metric measurement, a typical British compromise!

The conversion rate between a kilometre and a mile is very approximately the Golden Ratio (about 1.6). The Golden Ratio is a mathematical constant - the limit of the ratio of successive Fibonacci numbers. It also occurs in pleasant proportions in art and architecture. This is entirely coincidence and doesn't mean anything, but it might help some mathematicians with the conversion!

If you want an accurate conversion:

1 inch = 2.54 cm
1 foot = 30.48 cm
1 yard = 91.44 cm
1 mile = 1.609344 km
1 cm = .3937 ins
10 cm = 3.937 ins
1 m = 1 yard 3.37 ins
1 km = 0.6213711 miles

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