acalculator

How do I convert acres to hectares?

Type a value in either box, and the answer shows it in the other unit as you type.

Your numbers

Hectares (ha)
0.404686

1 ac = 0.404686 ha.

Hectares (ha): 0.404686. 1 ac = 0.404686 ha.

Hectares (ha) by acres (ac)

How to calculate

Converts acres (ac) to hectares (ha) and back, with the exact unit definitions.

Example with the default inputs (Acres (ac) 1): 1 ac = 0.404686 ha.

Formula: ha = ac × 0.40468564224

  • 1 acre = 0.40468564224 hectares, from 1 acre = 43,560 square feet of the international foot (NIST).
  • Exact on the typed decimals: at most 6 decimal places (6 significant digits below 0.0001), rounded half up; an answer of 1 billion or more shows at most 15 significant digits.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Acres (ac) 1 gives Hectares (ha) 0.404686.Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8
  2. Acres (ac) 100 gives Hectares (ha) 40.468564.Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8
  3. Hectares (ha) 100 gives Acres (ac) 247.105381.Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8

Other questions people ask

How many hectares are in an acre?

1 acre is 0.404686 hectares, from the exact unit definitions (NIST).

How do I convert acres to hectares?

Multiply by 0.404686: ha = ac × 0.40468564224. For example, 1 ac × 0.404686 = 0.404686 ha.

How do I convert hectares back to acres?

Multiply by 2.471054, or type the hectares into the second box and the converter works it out. 1 hectare is 2.471054 acres.

Why is an acre 0.40468564224 ha?

An acre is 43,560 square feet. With the international foot of 0.3048 m that is 4,046.8564224 m² exactly (NIST), and a hectare is 10,000 m², so 1 acre is 0.40468564224 ha.

What about the survey acre?

Older US land records may use the survey foot, which makes an acre about 4,046.873 m², 4 parts per million more. NIST made the survey foot obsolete from January 1, 2023; this page uses the international acre.

What is 100 acres in hectares?

40.468564 ha: 100 × 0.40468564224.