How do I convert acre to km²?

Use the formula shown above or enter a value to see acre converted to km² instantly.

What is the formula for acre to km²?

The converter calculates km² by applying the category-specific conversion factor for Area.

When should I use acre vs km²?

acre and km² are both part of the Area category; pick the unit that matches your measurement context (e.g., scale, region, or industry standard).

Area Converter & Surface Reference

Convert acre to km²

Use the live converter below to translate between Acre (acre) and Square Kilometer (km²). Scroll further for quick examples, formula tips, and related units.

Formula insight: Most unit conversions use a simple multiplication or division by a conversion factor. The calculator shows the exact formula used.

Convert

acre → km²

Acre

acre

Square Kilometer

0.004

km²

Rounded result (4 decimals max)

Formula

1 acre = 0.004 km²

Conversion sourcesTap or click to view references

The International System of Units (SI) — NIST Special Publication 330
National Institute of Standards and Technology (NIST). The SI Brochure (SP 330) is the definitive English edition of the BIPM SI tables. NIST’s edition lists the official constants and conversion factors tying inch-pound units to SI, which SwapUnits applies for length, mass, temperature, pressure, volume, and related conversions. See /standards/nist-si-tenfold for the complete decimal multiple/submultiple table. View source · View SI table

Results update as you type. Swap the direction to convert back from km² to acre.

Back to main converter

acre to km² quick table

Multiply any row by the same factor to scale results. Use the converter above to enter exact values with your own units.

Acre (acre)	Square Kilometer (km²)
0.25 acre	0.001 km²
0.5 acre	0.002 km²
1 acre	0.004 km²
2 acre	0.0081 km²
5 acre	0.0202 km²
10 acre	0.0405 km²
25 acre	0.1012 km²
100 acre	0.4047 km²

km² back to acre

Keep the reciprocal handy when double-checking calculations or undoing a conversion.

Square Kilometer (km²)	Acre (acre)
0.25 km²	61.7763 acre
0.5 km²	123.5527 acre
1 km²	247.1054 acre
2 km²	494.2108 acre
5 km²	1,235.5269 acre
10 km²	2,471.0538 acre
25 km²	6,177.6345 acre
100 km²	24,710.5381 acre