Acres to Square Miles (mi²) Converter
Enter a value to instantly convert between area units.
1 Acre = 0.0016 Square Mile
Key Formulas
Acre → Square Foot
ft² = ac × 43560Square Foot → Acre
ac = ft² × 0.0000229568Hectare → Acre
ac = ha × 2.47105Acre → Hectare
ha = ac × 0.404686Formula
mi² = acres × 0.0015625One acre equals exactly 1/640 of a square mile — since 640 acres = 1 mi². This is a clean, memorable relationship: divide acres by 640 to get mi², or multiply mi² by 640 to get acres. US county planning, land management, and geographic databases frequently use both units interchangeably.
Source: NIST SP 811, Table B.8
Frequently Asked Questions
Real-World Examples
A land manager noting that 640 acres = 1 mi² — a useful rule of thumb for quick area estimation.
640 ac = 1 mi²
A county planner calculating 160 acres (quarter section) = 0.25 mi² for zoning district analysis.
160 ac = 0.25 mi²
A real estate analyst converting 320 acres (half section) = 0.5 mi² for development density calculation.
320 ac = 0.5 mi²
An environmental scientist converting 1280 acres (2 mi²) to mi² for watershed boundary delineation.
1280 ac = 2 mi²