Square metres to ping (坪)

The formula

ping = square metres × 0.3025

This factor is exactly 0.3025 — not a rounding, not a convenient approximation. It is 121/400, the reciprocal of the ping’s own definition, and it is the tidiest conversion factor anywhere in this catalogue.

To go the other way, multiply by 400/121 = 3.3057851. See ping to square metres.

Why it is exact

A ping is six 台尺 square, and a 台尺 is exactly 10/33 of a metre:

1 坪 = (20/11)² m² = 400/121 m²
1 m² = 121/400 坪 = 0.3025 坪

121/400 terminates in decimal because 400 is 2⁴ × 5². Very few traditional units convert this cleanly into metric — most, like the acre at 4046.8564224 m², do not come close.

Two consequences worth knowing:

1 公頃 (hectare) = 3025 坪 exactly
1 平方公里 = 302,500 坪 exactly

Quick reference

100 m² is 30.25 ping — the single most useful anchor in this conversion, and easy to remember because the digits of the factor reappear.

Reading an international listing in Taiwanese terms

Property outside Taiwan is quoted in square metres or square feet, so this is the conversion for judging whether a flat abroad is bigger or smaller than the one you know:

A Hong Kong flat advertised at 700 sq ft is 65 m², which is 19.7 ping — though the two markets measure different things, so the comparison needs the caveat below.

Which area is being converted

Taiwanese listings quote the registered area (權狀坪數), which includes a share of the building’s common areas. European and American listings usually quote interior floor area only. Converting a European 100 m² into 30.25 ping therefore understates how it compares to a Taiwanese 30 ping apartment, because the Taiwanese figure has 30% of common area folded into it and the European one does not.

See ping to square metres for the 公設比 table.

Land, and the units above the ping

Estimating in your head

Divide by 3 and take off a tenth, or simply multiply by 0.3 and add a little. 100 m² × 0.3 is 30 ping, against a true 30.25 — under 1% out, and the exact answer is only one more digit away.