Tools for Estimating the Size of an Area
Full Sheet w/ conversions for miles, kilometers, acres. Resolution to 0.01 sq. mi at 1:24,000 scale.
You'll need a calculator with this one.
Pocket Sized Tools
1:24,000 Square Miles (1 sq. mi., resolution to 1/100th of a sq. mi.)
1:24,000 Kilometers (1 sq. km, resolution to 1/100th of a sq. km, also good as a UTM Grid)
1:24,000 Acres ( ~3.5" X 3.5", resolution to 10 acres)