How do you convert square miles to acres?

To convert square miles (mi²) to acres (ac), multiply the area in square miles by 640 (acres = square miles × 640).

What is 2.5 square miles in acres?

2.5 square miles (2.5 mi²) is equal to 1,600 acres (1,600 ac).

Which is larger, 1 square mile (mi²) or 1 acre (ac)?

One square mile (mi²) is larger than one acre (ac). Specifically, 1 mi² contains 640 ac, whereas 1 ac is 0.0015625 mi².

How do I convert back from acres (ac) to square miles (mi²)?

To reverse the calculation from ac to mi², multiply your acre value by the inverse factor 0.0015625 (or divide by 640). You can also click the Swap button in the tool above to flip directions in one click.

Are there regional or standard differences when converting mi² and ac?

International Foot vs. US Survey Foot: Under the 1959 International Yard and Pound Agreement, 1 international foot is defined as 0.3048 meters. Legacy US land deeds and State Plane Coordinate Systems prior to 2023 used the US Survey Foot (1200/3937 m ≈ 0.3048006096 m), a difference of 2 parts per million (about 0.01 ft per mile).

Square Miles to Acres Converter

Enter the area in square miles below to convert it to acres.

Acres to Square Miles (ac → mi²)

Convert Square Miles to Acres

Enter a value in square miles (mi²) to convert to acres (ac).

Value (mi²)

From

Result

•

1,600acres

2.5 mi² = 1,600 ac

Result updates automatically

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Equivalent Measurements Across UnitsFor 2.5 mi²

Acres1,600 ac

Suggested Conversions

Reference:NIST OWM (SI Units — Length & Area)

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Square Mile to Acre Conversion Table

Table showing various square mile measurements converted to acres. Click any preset value or arrow to load it into the converter.

Square Miles (mi²)	Acres (ac)
1 mi²	640 ac
1.25 mi²	800 ac
2 mi²	1,280 ac
2.5 mi²	1,600 ac
5 mi²	3,200 ac
10 mi²	6,400 ac
12.5 mi²	8,000 ac
15 mi²	9,600 ac
20 mi²	12,800 ac
25 mi²	16,000 ac

How to Convert Square Miles to Acres

To convert square miles to acres, multiply the area by the following conversion ratio: 640 acres/square mile.

Since one square mile is equal to 640 acres, you can use this simple formula to convert:

acres = square miles × 640

The area in acres is equal to the area in square miles multiplied by 640.

For example, here's how to convert 2.5 square miles to acres using the formula above.

acres = (2.5 mi² × 640) = 1,600 ac

How Many Acres Are in a Square Mile?

There are 640 acres in a square mile, which is why we use this value in the formula above.

1 mi² = 640 ac|1 ac = 0.0015625 mi²

Our square mile to acre calculator automatically converts your area measurements with full decimal and scientific precision across US customary, imperial, and SI metric standards.

Square Miles and acres are both units used to measure area. Keep reading to learn more about each unit.

What Is a Square Mile?

A square mile is a unit of area equal to 2,589,988.110336 square meters (m²), the base unit for area. Equal to 640 acres or 2.589988 km². [1]

The square mile is classified as a US customary and imperial unit of area. Square Miles can be abbreviated as mi²; for example, 1 square mile can be written as 1 mi².

When working with square miles (mi²) in formulas or technical specifications, always verify whether your target system uses SI metric, US customary, or British imperial standards.

In practice, square miles (mi²) are widely used across large-scale industrial, bulk, and macro-level area specifications within US customary and imperial workflows, engineering documentation, and technical data sheets.

Learn more about square miles in our Area Converter.

What Is an Acre?

An acre is a unit of area equal to 4,046.8564224 square meters (m²), the base unit for area. Imperial & US Customary land unit equal to 43,560 square feet. [2]

The acre is classified as a US customary and imperial unit of area. Acres can be abbreviated as ac; for example, 1 acre can be written as 1 ac.

When working with acres (ac) in formulas or technical specifications, always verify whether your target system uses SI metric, US customary, or British imperial standards.

In practice, acres (ac) are widely used across large-scale industrial, bulk, and macro-level area specifications within US customary and imperial workflows, engineering documentation, and technical data sheets.

Learn more about acres in our Area Converter.

When converting area between square miles (mi²) and acres (ac), keep full floating-point precision (1 mi² = 640 ac; 1 ac = 0.0015625 mi²) during intermediate calculations and round only the final acre figure to match your instrument tolerance.

More Square Mile & Acre Conversions

Need to calculate in the opposite direction? Use our acres to square miles converter (ac to mi²) to switch your starting unit immediately. You can also explore related tools such as converting hectares to acres, converting square feet to acres, or converting square miles to square kilometers.

Convert from Square Miles

Convert to Acres

Frequently Asked Questions

There are 640 acres (ac) in 1 square mile (mi²). Conversely, 1 acre (ac) is equal to 0.0015625 square miles (mi²).

Area Converter

Quick Info

Direct Factor: 1 square mile (mi²) equals 640 acres (ac).
Inverse Factor: 1 acre (ac) equals 0.0015625 square miles (mi²).
Formula: acres = square miles × 640.
Standard Note: International Foot vs. US Survey Foot: Under the 1959 International Yard and Pound Agreement, 1 international foot is defined as 0.3048 meters. Legacy US land deeds and State Plane Coordinate Systems prior to 2023 used the US Survey Foot (1200/3937 m ≈ 0.3048006096 m), a difference of 2 parts per million (about 0.01 ft per mile).

Units Comparison

Square Mile (mi²)

Equal to 640 acres or 2.589988 km².

Acre (ac)

Imperial & US Customary land unit equal to 43,560 square feet.

Square Meter (m²)

SI derived unit of surface area.

References

[1]NIST OWM · SI Units — Length & Area
Source
[2]NIST HB 44 · Acre, Hectare & Land Survey Tables
Source
[3]NIST SP 811 · NIST SP 811 App. B.9 (Area)
Source

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References

NIST · BIPM · ISO

[1]
NIST OWM (SI Units — Length & Area)·Area Metrology Standard — Square Miles (mi²) to Acres (ac)
NIST OWM Standard
[2]
NIST HB 44 (Acre, Hectare & Land Survey Tables)·Unit Specifications: Square Mile (mi²) & Acre (ac)
NIST HB 44 Specification
[3]
NIST SP 811 (NIST SP 811 App. B.9 (Area))·Conversion Factors & Mathematical Basis (mi² to ac)
NIST SP 811 Reference

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