Imperial units of area

4840 square yards= 1 acre
640 acres= 1 square mile
1 furlong x 1 chain= 1 acre
10 square chains= 1 acre
1210 square yards= 1 rood
1 pole x 1 pole= 1 square pole (sometimes called a pole)
40 (square) poles= 1 rood
1 furlong x 1 pole= 1 rood
4 roods= 1 acre
A pole is the same length as a rod or a perch.
A rod or perch may also be a measure of area.