Square miles to Acres Converter
Convert Square miles (mi²) to Acres (ac) instantly, or use the conversion table below to look up common values.
Square miles to Acres conversion table
| Square miles (mi²) | Acres (ac) |
|---|---|
| 1 | 640 |
| 2 | 1,280 |
| 3 | 1,920 |
| 4 | 2,560 |
| 5 | 3,200 |
| 10 | 6,400 |
| 25 | 16,000 |
| 50 | 32,000 |
| 100 | 64,000 |
How to convert Square miles to Acres
1 mi² equals 640 ac. Use the converter above for any value, or read the table for common conversions.
ac = mi² × 640 · mi² = ac × 0.0015625Multiply a square miles figure by 640 to get acres, or divide it by 0.001563 to go the other way.
Worked examples
- 1 mi²= 640 ac
- 5 mi²= 3,200 ac
- 10 mi²= 6,400 ac
- 25 mi²= 16,000 ac
- 100 mi²= 64,000 ac
What these units are
Square miles (mi²). A square mile is about 2.59 square kilometers, or exactly 640 acres. It is used for land and territory areas in the United States and the UK, and for large ranch or park sizes.
Acres (ac). An acre is 4,046.8564224 square meters, about 0.4047 hectares. It is the traditional land unit of the UK and US and is still used for land in parts of East Africa.
Every factor is an exact definition, so the only loss is display rounding. Land figures quoted in acres and hectares are usually rounded at the source.
Converting Square miles to Acres in practice
Working in square miles
A square mile is the area of a square one mile on each side, exactly 2.589988110336 square kilometers, or exactly 640 acres. It is built from the statute mile and never from the nautical mile.
Metropolitan areas, counties, states, large ranches and national parks are measured in square miles in those countries. Weather maps and watershed studies also report extents in square miles.
The relation to acres is exact, with 640 acres in one square mile, and the relation to square kilometers follows from the exact definition of the mile. Rounded display can perturb the last digit of a two-way conversion.
Treating square miles as if they were mile figures is the usual slip: an area scales with the square of the length, so a square mile is not 1.609 square kilometers. Land is often better compared in acres or hectares.
Square miles, acres and square kilometers all describe large areas, and the relations are exact: 640 acres to a square mile, 2.59 square kilometers to the same measure. A county in one unit and a park in another do not compare until both are converted.
Reading the result in acres
An acre is exactly 4,046.8564224 square meters, an area of 4,840 square yards, or one chain by one furlong. It is a unit of area, not of length.
Land titles, farm sizes, plots and ranches are described in acres in the United States, the United Kingdom and parts of the Commonwealth. Estate agents quote plot sizes in acres.
One acre equals 0.40468564224 hectares exactly, and a square mile holds exactly 640 acres. The site rounds displayed output, so a figure converted to hectares and back may return one digit away.
The classic mistake is treating an acre as a square of fixed side length; it is any shape with that area, and an acre is roughly 209 feet square only when square. Quoting acres from a deed written in hectares also invites error.
Acres and hectares both describe land, with one acre under half a hectare. A plot stated in hectares is about 2.47 times the same number of acres, so quoting the wrong unit makes land look far larger or smaller.
Checking a square miles to acres conversion
Area factors are the square of the corresponding length factors, so the numbers move much faster than a reader expects. A square meter contains 10,000 square centimeters, and a square kilometer a million square meters, not a thousand.
The units that share a name across systems are still different sizes: a square mile and a square kilometer differ by a factor of about 2.59, and an acre is a fixed area rather than a square with equal sides, so it does not convert like the length units it is named after.
Land is where the reciprocal matters most, because acres and hectares are both in use for the same plots. When a figure moves between them, check it against a shape you can picture — a hectare is a square 100 meters on each side — rather than against the number alone.
Tanzania reference points
Real quantities, converted into the units on this page.
The total surface area of Tanzania, including Zanzibar
947,303 km² = 365,755.733094 mi² = 234,083,669.17999 ac
Source: UN Statistics Division — World Statistics Pocketbook, country profile: Tanzania · verified 2026-09-14
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