Acre to Square Mile Converter
Area · unit-converter
Convert Acre to Square Mile with a fixed input and output unit, step-by-step formula line, and reference tables. All calculations use square-meter-based definitions (international feet / yard standards, acre, hectare, and regional units like pyeong/tsubo).
Calculator
From: Acre (ac)
To: Square Mile (mi2)
About Acre
The international acre is 4,046.8564224 m² by definition. Acres are standard for rural and suburban land in the US and still appear in UK property contexts.
About Square Mile
The square mile is an imperial and US customary unit of area equal to the area of a square one statute mile on a side. It is common for large land parcels and geography in the US and UK.
How to convert acres to square miles
1 acre is equal to 0.0015625 square mile:
1 ac = (4046.8564224 m² ÷ 2589988.110336 m²) mi2 = 0.0015625 mi2
Each acre is defined as 4046.8564224 m² and each square mile as 2589988.110336 m², so one ac equals 4046.8564224 ÷ 2589988.110336 mi2 = 0.0015625 mi2.
Let a(ac) be the numeric value of the same area measured in Acre (ac), and a(mi2) the value in Square Mile (mi2). Then:
a(mi2) = a(ac) × (4046.8564224 / 2589988.110336)
Equivalently, divide by how many ac fit into one mi2 (m² per mi2 divided by m² per ac):
a(mi2) = a(ac) ÷ 640
Or: square mile = acre ÷ 640
Examples
Example #1: Convert 20 ac to square mile
20 ac = 20 ac × (4046.8564224/2589988.110336) mi2 = 0.03125 mi2
20 ac = 20 ac ÷ 640 = 0.03125 mi2
Example #2: Convert 50 ac to square mile
50 ac = 50 ac × (4046.8564224/2589988.110336) mi2 = 0.078125 mi2
50 ac = 50 ac ÷ 640 = 0.078125 mi2
Summary
To convert Acre to Square Mile, multiply the value in ac by the ratio of square meters per ac divided by square meters per mi2. Equivalently: value_mi2 = value_ac × (4046.8564224 / 2589988.110336). Numerically, 1 ac equals 0.0015625 mi2.
Relationship context
Both units belong to US customary / imperial area measures. Relationships such as 9 ft² per yd² and 43,560 ft² per acre are exact under standard definitions. This tool uses SI-based square-meter factors for consistency.
Conversion tables
| Acre (ac) | Square Mile (mi2) |
|---|---|
| 0.1 | 0.00015625 |
| 1 | 0.0015625 |
| 2 | 0.003125 |
| 3 | 0.0046875 |
| 4 | 0.00625 |
| 5 | 0.0078125 |
| 6 | 0.009375 |
| 7 | 0.0109375 |
| 8 | 0.0125 |
| 9 | 0.0140625 |
| Acre (ac) | Square Mile (mi2) |
|---|---|
| 10 | 0.015625 |
| 20 | 0.03125 |
| 30 | 0.046875 |
| 40 | 0.0625 |
| 50 | 0.078125 |
| 60 | 0.09375 |
| 70 | 0.109375 |
| 80 | 0.125 |
| 90 | 0.140625 |
| 100 | 0.15625 |