In the metric system, land area is measured in hectares. A hectare (ha) is 100 meters (m) x 100 m, 10,000 m². In the United States, land area is most commonly expressed in acres. There are 2.47 acres in 1 ha. The conversion from hectares is relatively easy to do without a calculator;
rounding to two significant figures gives 2.5 acres in 1 ha.

If a natural preserve is 100 ha, what is the size in acres? 100 ha x 2.5 acres/ha = 250 acres.

Let's try another problem, how many acres in 157 ha? (one decimal place) acres

Now let's convert to hectares.
A particular forest is 10,000 acres. Determine the size if hectares.
ha