Square Miles (mi²) to Acres Converter
Enter a value to instantly convert between area units.
1 Square Mile = 640 Acre
Key Formulas
Acre → Square Foot
ft² = ac × 43560Square Foot → Acre
ac = ft² × 0.0000229568Hectare → Acre
ac = ha × 2.47105Acre → Hectare
ha = ac × 0.404686Formula
acres = mi² × 640One square mile equals exactly 640 acres — by US survey definition. This is a fixed relationship that every US surveyor, real estate agent, and land manager knows: multiply mi² by 640 to get acres. Counties are often measured in mi² while individual properties are measured in acres.
Source: NIST SP 811, Table B.8
Frequently Asked Questions
Real-World Examples
A real estate agent noting that 1 mi² = 640 acres for US land listing comparisons.
1 mi² = 640 ac
A rancher calculating 5 mi² (3200 acres) grazing lease for cattle carrying capacity analysis.
5 mi² = 3200 ac
A county assessor converting 25 mi² jurisdiction to acres for tax district administration.
25 mi² = 16000 ac
A forest manager converting 100 mi² timber stand to acres for harvest scheduling and yield estimation.
100 mi² = 64000 ac