Which is the most confusing unit of measurement?

34 votes
Hectares
12%
7 votes
Tons
3%
78 votes
Rods and chains
28%
3 votes
Metres squared
1%
58 votes
Grams per acre
21%
25 votes
Yield in tonnes per acre
9%
18 votes
Board-feet
7%
52 votes
Stone
19%