Convert Acre to Square Kilometer (ac → km²)

Converting acres to square kilometers is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in acres

   Start with the number of acres (ac) you want to convert.
2. 2
   Multiply by 0.004047

   The conversion factor from ac to km² is 0.004047. Multiply your value by this number.
3. 3
   Read the result in square kilometers

   The result is your value in square kilometers (km²).

Multiply the value in acres by 0.004047. For the reverse direction, multiply by 247.10538.

• ✓1 acre = 43,560 ft² = 0.4047 ha.
• ✓640 acres = 1 square mile — a "section" in US land survey.
• ✓An acre is 43,560 ft² — a useful number for US real-estate calculations.

• ✗Using "acre" in modern European property — use hectares or m² instead.
• ✗Assuming an acre is a specific shape — it is only an area (any shape).
• ✗Multiplying acres by 4000 m² — correct value is 4046.86.

What is the Acre?

The acre equals exactly 4,046.8564224 square meters (or 43,560 square feet) and is the standard unit for American and British farmland, real estate, and recreational property. The unit's origin is medieval: an acre was the area a yoke of oxen could plow in one day, traditionally a strip 1 furlong (660 ft) by 1 chain (66 ft). Despite metric adoption in many fields, the acre persists in property records throughout the US and UK. A standard American football field (excluding end zones) is about 1.32 acres. The largest US state, Alaska, contains about 365 million acres. The acre relates to the square foot (43,560 ft² = 1 acre), the hectare (1 ha ≈ 2.471 acres), the square mile (640 acres = 1 mi²), and the square meter (1 acre ≈ 4,047 m²). US farms average around 446 acres, and the average UK farm is about 215 acres.

• US farmland and ranches
• UK rural property and estates
• Canadian rural property (legal survey system)

What is the Square Kilometer?

The square kilometer equals 1,000,000 square meters (or 100 hectares) and is the international standard for measuring large areas: cities, national parks, lakes, watersheds, and country-level statistics. Population density is conventionally given in people per km² (e.g., Singapore has roughly 8,400 people/km², Mongolia has fewer than 2). The largest US national park, Wrangell-St. Elias in Alaska, covers about 53,000 km². France is 643,801 km², and the largest country, Russia, spans 17 million km². The square kilometer relates to the square meter (1 km² = 1,000,000 m²), the hectare (1 km² = 100 ha), the square mile (1 km² ≈ 0.386 mi²), and the acre (1 km² ≈ 247.1 acres). Geographic information systems, climate science, and regional planning all rely on square kilometers as the base unit for area.

• Country and city geographic area reporting
• National-park and protected-area sizes
• Large-scale environmental studies (deforestation, etc.)