About the Area Converter

The area converter translates between ten units of area: square millimetre, square centimetre, square metre, square kilometre, hectare, acre, square foot, square inch, square yard, and square mile. All conversions are expressed in square metres as the pivot unit, with the factors derived from the square of the corresponding length conversion.

Area units are the square of length units, so the conversion factors are the squares of the length factors. One square metre equals 10.7639 square feet because 1 metre equals 3.28084 feet and 3.28084 squared is 10.7639. The same applies to all other units: square the linear factor to get the area factor.

The hectare is a non-SI unit accepted for use with SI, defined as exactly 10,000 square metres (a square 100 metres on each side). It is the standard unit for measuring land area in most of the world. The acre is the imperial counterpart, defined as 43,560 square feet or approximately 4046.86 square metres. Per the 1959 International Yard and Pound Agreement, the acre is exactly 4046.8564224 square metres.

The converter handles any real input, including negatives (which can arise in signed-area calculations in surveying) and zero. All metric-to-metric factors are exact powers of ten; the imperial factors are defined exactly in terms of the metre.

How It Works

The converter uses the two-step method through square metres:

base_in_m2 = value * factor[from]
result = base_in_m2 / factor[to]

The factor table (in m²) is:

mm² = 0.000001 m²     cm² = 0.0001 m²       m² = 1 m²
km² = 1,000,000 m²    ha  = 10,000 m²       ac = 4046.86 m²
ft² = 0.092903 m²     in² = 0.00064516 m²   yd² = 0.836127 m²
mi² = 2,589,988 m²

Each factor is the area in square metres that one unit represents. For metric units, the factors are exact powers of ten. For imperial units, the factors are the squares of the linear factors defined by the 1959 International Yard and Pound Agreement: 1 ft² = (0.3048)² = 0.09290304 m², displayed as 0.092903 for readability.

The hectare and acre are land-area units, not squares of any single linear unit. The hectare is exactly 10,000 m² by definition. The acre is 43,560 ft² = 4046.8564224 m² exactly, displayed as 4046.86 for readability.

The two-step method through square metres keeps the code simple and makes the conversions transparent. The pivot unit also matches the SI convention, which expresses area in m².

Worked Examples

Converting 1 acre to square metres: the input in m² is 4046.86 m², displayed directly. Converting to hectares gives 4046.86 / 10000 = 0.404686 ha. This explains why a 2.5-acre plot is roughly 1 hectare — the popular approximation used in real estate.

Converting 1 square mile to square kilometres: the input in m² is 2,589,988 m², and the result is 2,589,988 / 1,000,000 = 2.58999 km². The popular approximation "1 square mile is about 2.6 square kilometres" is therefore accurate to within 0.4 percent.

Converting 100 square feet to square metres: the input in m² is 100 * 0.092903 = 9.2903 m², displayed directly. This is the area of a 10-foot by 10-foot room, which in metric terms is approximately 3.05 metres by 3.05 metres.

When to Use This Tool

Use the area converter when you need to:

Convert land area between hectares and acres for international real estate.
Translate floor plans between square feet and square metres.
Compute the area of a property from its dimensions in different units.
Convert agricultural yield measurements between hectares and acres.
Translate printed circuit board or fabric dimensions between square millimetres and square inches.
Compute the surface area of materials for construction or manufacturing.
Convert geographical areas between square miles and square kilometres.

Limitations & Disclaimer

This converter uses exact conversion factors defined in SI and the 1959 International Yard and Pound Agreement. It does not handle circular area units, the Chinese mu, the Japanese tsubo, or other regional units. Results are subject to IEEE 754 floating-point precision for very large or very small magnitudes. The acre conversion uses the international acre, which differs slightly from the US survey acre (by about 4 parts per million). See our disclaimer for full details.

Frequently Asked Questions

Why is the hectare not an SI unit?

Although the hectare is not an SI base or derived unit, it is accepted for use with SI per the SI Brochure 9th edition, Table 6. It is convenient because it is roughly the size of a small farm field (100 metres on each side) and avoids the large numbers that would arise from expressing land areas in square metres.

How is the acre defined?

The acre was originally defined as the area that a team of oxen could plough in one day. It is now defined exactly as 43,560 square feet, which is 4046.8564224 square metres per the 1959 International Yard and Pound Agreement. One acre is approximately 0.4047 hectares.

Why are area factors the squares of length factors?

Because area is a two-dimensional quantity: it is length times width. If you double the linear size of an object, its area quadruples (factor of 2 squared). Similarly, if 1 foot equals 0.3048 metres, then 1 square foot equals (0.3048) squared = 0.09290304 square metres.

What is the difference between a square mile and a section?

A section is a unit of land surveying in the US Public Land Survey System, defined as exactly 1 square mile (640 acres). A township consists of 36 sections. The terms are used in the western United States for describing land parcels.

Does the converter handle circular areas?

No, this converter handles only units of area, not shapes. To compute the area of a circle from its radius, multiply pi by the radius squared. The result can then be converted to any unit using this tool.

Are the hectare and acre conversion factors exact?

The hectare is exactly 10,000 m² by definition. The acre is exactly 43,560 ft², which equals 4046.8564224 m² per the 1959 International Yard and Pound Agreement. The square-foot factor (0.09290304 m²) is the square of the exact foot definition. The displayed values are rounded for readability; the actual computation uses full precision.

Last updated: September 9, 2026 · Author: HT99 Tools Editorial Team