How many acres are in a square mile?

Exactly 640 acres equal 1 square mile. This is a defined relationship in the US customary and imperial systems.

What is the conversion factor from acres to square miles?

1 acre = 0.0015625 square miles (which is 1 ÷ 640). Multiply any acreage by 0.0015625 to get square miles.

How large is 1 acre in square miles?

1 acre is 0.0015625 square miles, or about 1/640th of a square mile.

How do I convert square miles to acres?

Multiply square miles by 640. For example, 2.5 square miles × 640 = 1,600 acres. This tool's reverse converter does it automatically.

Why use square miles instead of acres?

Square miles are more intuitive for very large areas such as counties, states, forests, or bodies of water. Acres are more common for smaller parcels like farms or lots.

Acres to Square Miles Converter

Enter an area in acres and instantly see the equivalent in square miles using the exact conversion factor.

Acres to Square Miles

1 acre = 0.0015625 sq mi (1/640)

Acres

Square Miles

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Square Miles to Acres

1 sq mi = 640 acres (exact)

Square Miles

Acres

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Quick Reference Table

Acres	Square Miles

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Summary

This tool converts acres to square miles using the exact conversion factor: 1 acre equals 0.0015625 square miles (or 1/640). Enter any acreage value and the equivalent square miles result appears instantly. You can also convert square miles back to acres.

How it works

Enter the number of acres in the input field.
The converter applies the exact factor: acres × 0.0015625 = square miles.
The result displays instantly — no button click required.
Use the reverse converter to go from square miles back to acres.
Copy either result with one click.

Use cases

Convert large land parcels from acres to square miles for mapping.
Compare land area in different units for real estate analysis.
Calculate the size of counties, states, or national parks in square miles.
Convert agricultural field measurements for reporting.
Verify land area figures in legal or survey documents.
Understand geographic scale when acreage figures are cited in news.

Frequently Asked Questions

Last updated: 2026-10-05 · Reviewed by Nham Vu