Hectares to square kilometers (ha to km2)

One hectare is exactly 0.01 square kilometers. A hectare is a 100-meter square and a square kilometer a 1,000-meter square, so the side is ten times longer and the area a hundred times larger.

Worked through: 100 ha x 0.01 = 1 km2.

Going the other way, one square kilometer is 100 hectares.

For mental arithmetic: Divide by 100.

Wildfires, national parks and urban areas are reported in both units, sometimes in the same article, and the factor of a hundred is easy to drop. A 25,000-hectare fire is 250 square kilometers, or about 96.5 square miles. The other trap is the spoken form: '2 kilometers squared' can mean 2 km2, or a square 2 km on a side, which is 4 km2. Written with the superscript, km2 always means the first, and that is what this converter uses.

Precision is worth matching to the input. A measurement given as 1 ha carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.