Hectares to Acres Calculator

How the hectares to acres conversion works

A hectare is a metric unit of area equal to 10,000 square metres (m²), or a square 100 m on each side. An acre is an imperial unit of area equal to 4,046.8564224 m². The two are linked by a fixed, defined factor: one hectare equals 2.47105 acres. Enter an area in hectares and the calculator multiplies it by that factor to give acres, then derives the square-metre equivalent (ha × 10,000) and the square-kilometre equivalent (ha ÷ 100). Nothing here is an estimate — the conversion is exact, and the only figure that carries uncertainty is the hectarage entered.

The exact conversion factor

Because a foot is defined as exactly 0.3048 m, one square foot is 0.09290304 m² exactly. An acre is defined as 43,560 square feet, giving 43,560 × 0.09290304 = 4,046.8564224 m² exactly. One hectare is exactly 10,000 m², so dividing gives 10,000 ÷ 4,046.8564224 = 2.47105 acres (to five decimal places). The calculator applies the full-precision factor; the displayed result rounds to four decimal places for acres, two for square metres, and four for square kilometres.

What a hectare actually measures

The hectare (symbol: ha) is a unit in the International System of Units defined as 1 hm² — the area of a square 100 metres on each side. It sits outside the strict SI but is accepted for use with it, and the BIPM lists it as a non-SI unit whose continued use is sanctioned. In practice it is the standard metric unit for land area across Europe, Australia, and most of the Commonwealth. A football pitch in England is typically around 0.7 ha; a square kilometre is 100 ha.

Hectares, acres, and square metres compared

One hectare is 10,000 m², 2.47105 acres, and 0.01 km². One acre is 0.404686 ha and 4,046.86 m². For land areas larger than a few building plots, hectares are the metric unit seen most often on Ordnance Survey mapping, agricultural records, and planning documents. Acres persist in older title deeds, estate-agent particulars for rural property, and farm tenancy agreements. The calculator shows all four outputs — acres, square metres, and square kilometres — so a figure quoted in any common unit reads across to the others without a second lookup.

Worked examples

One hectare converts to 2.4710 acres (10,000 m², 0.0100 km²). A 2.5 ha paddock converts to 6.1776 acres (25,000.00 m², 0.0250 km²). A 0.5 ha allotment site converts to 1.2355 acres (5,000.00 m², 0.0050 km²). Each result follows directly from the single conversion factor with no intermediate rounding step that would compound error.

Where hectares still appear in UK practice

Ordnance Survey maps, Land Registry title plans, and local planning authority site areas are given in hectares for agricultural-scale land. Development density is expressed as dwellings per hectare (dph) in National Planning Policy Framework guidance. Estate-agent listings for farms, smallholdings, and rural estates frequently quote both hectares and acres side by side. Converting between the two is a routine step when comparing a marketing figure against an official planning record or Agricultural Holdings Act schedule.

Hectares on planning submissions

Building Regulations and planning documents in the UK are drawn up in metric units. Site areas on planning applications to an English local planning authority are expressed in hectares or square metres, not acres, so an acreage taken from a sales listing or an older deed converts to hectares before it aligns with what a planning officer or Building Control body works with. A figure such as 2.5 ha on a planning application equates directly to 25,000 m², which is 6.18 acres.

Precision and rounding

The conversion factor is exact to as many digits as needed, so precision is limited only by the hectarage entered and by sensible display rounding. The calculator shows acres to four decimal places, square metres to two, and square kilometres to four — each chosen to suit the scale of the unit. For survey-grade work, the area on a measured site plan is more reliable than a converted marketing figure, because the input measurement rather than the arithmetic sets the real accuracy.

Using this alongside other BuildMetricLab tools

The acres-to-square-metres calculator handles the reverse direction — enter acres and read back square metres, hectares, and square feet. Once a plot size is in square metres it feeds into area-based estimators for artificial grass, fencing, paving, or a concrete slab. The linear-to-square-metres calculator converts a length-and-width measurement into the same area unit. Every BuildMetricLab tool runs entirely in your browser — no sign-up, no data sent anywhere, and the formula is shown on the page so the maths can be audited.