Land area in hectares:
converting square metres and acres

What a hectare is, in terms you can picture

A hectare is a square measuring 100 metres on each side. That makes it 100 × 100 = 10,000 square metres. The metric system uses it for land because it sits in a comfortable range between the square metre, which is too small for fields, and the square kilometre, which is too large. Roughly, a hectare is a little bigger than a standard football pitch.

Official land records and agricultural statistics in India, and in most countries, report area in hectares even where local units such as acre, bigha or guntha are used on the ground.

The conversion from square metres

If your measurement is not already an area, get it first: length times width for a rectangular plot, or break an irregular parcel into rectangles and triangles and add them up.

Worked example: a 250 m by 140 m field

Converted to acres at about 2.471 acres per hectare, that is 3.5 × 2.471 = about 8.65 acres. Going the other way, 5 acres is 5 × 0.4047 = about 2.02 hectares, and 2.5 hectares is about 6.18 acres.

Acres, hectares and local units

The acre is defined as 4,046.86 square metres, or 43,560 square feet. One hectare is therefore 2.471 acres, and one acre is 0.4047 hectares. Those two figures are all you need to move between the metric and the traditional unit.

Local units are where problems start. A bigha, katha or guntha has a different size in different states and sometimes in different districts of the same state, so there is no single multiplier. Always confirm the local definition on the land record before converting, and do not trust a general internet value for a legal or financial purpose.

Measuring awkward plots

• Rectangles and squares: length times width, with both in the same unit.
• Triangular corners: base × height ÷ 2, using the perpendicular height.
• Trapezoid plots: average of the parallel sides times the distance between them.
• Irregular boundaries: split into the shapes above and add the pieces. For accuracy beyond that, use survey data or GPS area measurement.

Do each piece in square metres, add the pieces, and divide once by 10,000 at the end. That avoids rounding at every step.

Reading hectares in real documents

Hectare figures appear in land records, farm subsidy schemes, forest and wildlife statistics, and property listings. A small plot may be quoted in fractions: 0.25 ha is 2,500 m², about 0.62 acres. A farm of 3.5 hectares is classed as a small holding in many agricultural statistics, but thresholds differ by country and scheme, so check the definition in the document you are reading.

When a record gives area in two units, such as 1.2 ha and 2.97 acres, use the conversion above to check them against each other: 1.2 × 2.471 = 2.965 acres, so the figures agree after rounding. A mismatch is a prompt to ask which one is the official entry.

Fencing, seed and cost per hectare

Once area is in hectares, many cost figures are quoted per hectare. If seed is recommended at 25 kg per hectare, a 3.5 hectare field needs 87.5 kg. If fertiliser is applied at 120 kg of nitrogen per hectare, the field needs 420 kg of nitrogen in total, and you convert that to bags of fertiliser using the nutrient percentage on the label.

Perimeter is a separate figure. A rectangle 250 m by 140 m has a perimeter of 2 × (250 + 140) = 780 m, which is the length of fence to price. The same area can have very different perimeters, and a long thin plot costs more to fence than a square one of the same size: a 187 m square of 3.5 ha has a perimeter of only about 748 m.

When you record a result, state how you obtained it. An area derived from a tape and rectangle formula is a field estimate, while a surveyed area in the revenue record is a legal figure, and the two may differ by a few percent. Quote the hectare figure with a sensible number of decimals, usually two for farm plots and three for small parcels.

For very large areas, hectares also convert easily to square kilometres: 100 hectares make one square kilometre, so 350 ha is 3.5 km². This is handy for comparing a village's cultivated area with a district total, or for reading a forest or park size in a news report.

Lastly, keep an eye on map scale if you derive area from a printed map. Area scales with the square of the length scale: on a 1:10,000 map, 1 cm is 100 m, so a square of 1 cm × 1 cm on paper is a 100 m × 100 m square, exactly one hectare.

Common slips

1. 1Dividing by 100 instead of 10,000, which gives a figure 100 times too large.
2. 2Using the length in hectares: hectares measure area, not distance, so you cannot have a plot that is '2 hectares long'.
3. 3Mixing feet and metres. Convert everything to metres first (1 ft = 0.3048 m) or work in square feet and use 107,639 ft² per hectare.
4. 4Assuming a map's printed area is exact. Registered area can differ from the physically measured area.