Acres to square kilometers (acre to km²) converter

What is an acres to square kilometers converter?

An acres to square kilometers converter is an online tool that translates an area expressed in acres into its equivalent in square kilometers, and back again. The acre is a traditional unit of land area rooted in the Imperial and US customary systems, while the square kilometer belongs to the metric system. Because farmland, real estate listings and survey data are often quoted in acres in English-speaking countries but in square kilometers almost everywhere else, a reliable converter removes the guesswork when you need to compare parcels, report figures, or plan a project across measurement systems.

How it works

One acre is defined as exactly 4,046.8564224 square meters. Since a square kilometer contains 1,000,000 square meters (a kilometer is 1,000 meters, and area scales with the square of length), the relationship between the two units is fixed:

• 1 acre = 0.0040468564224 km²
• 1 km² = 247.105381467 acres (approximately)

To go from acres to square kilometers you multiply by the small factor 0.0040468564224. To reverse the direction you divide by that factor, which is the same as multiplying by roughly 247.105381467. The converter performs this arithmetic instantly and keeps both fields in sync, so editing either side updates the other.

Formula

To convert acres to square kilometers, multiply the number of acres by the conversion factor:

$\text{km}^2 = \text{acre} \times 0.0040468564224$

To convert square kilometers back to acres, divide by the same factor:

$\text{acre} = \frac{\text{km}^2}{0.0040468564224} \approx \text{km}^2 \times 247.105381467$

Acres to square kilometers conversion table

The table below lists common acre values alongside their square kilometer equivalents. Because an acre is a comparatively small unit, the square kilometer results are fractions until you reach large land areas.

Examples

Example 1: One acre to square kilometers

A single acre is a useful reference point. Applying the formula:

$1 \text{ acre} \times 0.0040468564224 = 0.0040468564224 \text{ km}^2$

So one acre equals roughly 0.004 km², which highlights just how small an acre is relative to a square kilometer.

Example 2: One square kilometer to acres

Working in the opposite direction, suppose a national park covers exactly 1 km² and you want the figure in acres:

$1 \text{ km}^2 \times 247.105381467 = 247.105381467 \text{ acres}$

A single square kilometer is therefore about 247 acres, a handy number to memorize for quick estimates.

Example 3: A 100-acre farm

A farmer with 100 acres of land wants to report the holding in metric units for an international grant application:

$100 \text{ acres} \times 0.0040468564224 = 0.40468564224 \text{ km}^2$

The 100-acre farm is just over four tenths of a square kilometer.

Notes

• The conversion factor is exact: 1 acre is defined as 4,046.8564224 m², so 1 acre = 0.0040468564224 km² with no rounding involved.
• The acre used here is the international (and US survey-equivalent for everyday purposes) acre. The difference between the international acre and the rarely used US survey acre is only about two parts per million and is negligible for almost all work.
• Because an acre is small compared with a square kilometer, expect lots of leading zeros when converting modest acreages; round the result to a sensible number of decimal places for reports.
• Keeping a single unit system throughout a project prevents mismatched figures and the costly errors they can cause.

Frequently asked questions

How many square kilometers are in one acre?

One acre equals 0.0040468564224 km². In other words, an acre is about four thousandths of a square kilometer.

How many acres are in one square kilometer?

One square kilometer is approximately 247.105381467 acres. For rough mental math you can use about 247 acres per square kilometer.

Is the acre to square kilometer conversion exact?

Yes. The international acre is defined as exactly 4,046.8564224 square meters, and a square kilometer is exactly 1,000,000 square meters, so the factor 0.0040468564224 carries no approximation.

How do I convert 100 acres to square kilometers?

Multiply 100 by 0.0040468564224, which gives 0.40468564224 km². A 100-acre area is therefore just over 0.4 square kilometers.

Why are my square kilometer results so small?

An acre is a relatively small unit of land. Since one square kilometer holds about 247 acres, any modest acreage converts to a small fraction of a square kilometer, producing several leading zeros.

Can this converter handle decimals and large values?

Yes. The acre to square kilometer converter accepts any decimal input and works for both tiny plots and very large land areas, updating both fields automatically as you type. For other area units, you can also use our area unit converter.