ThailandCalc guide
How to Read Rai–Ngan–Square Wah Measurements
Thai land sizes are often written as three components: Rai, Ngan and Square Wah. Understanding the hierarchy prevents one of the most common mistakes—treating the notation as a decimal number.
The mixed-unit format
A measurement written as 2 Rai 1 Ngan 35 Square Wah means exactly those three components. Since 1 Rai = 4 Ngan and 1 Ngan = 100 Square Wah, each part can be converted to a single common unit.
Convert the mixed figure to square meters
m² = (Rai × 1,600) + (Ngan × 400) + (Square Wah × 4)
For 2 Rai 1 Ngan 35 Square Wah: 3,200 + 400 + 140 = 3,740 m².
Convert the same figure to Rai
Rai = Rai + (Ngan ÷ 4) + (Square Wah ÷ 400)
2 + 0.25 + 0.0875 = 2.3375 Rai.
Why “2-1-35” is not 2.135 Rai
In shorthand, the three values may be separated by hyphens or spaces. They remain separate units. The middle number is Ngan and the final number is Square Wah. The notation works more like hours–minutes–seconds than an ordinary decimal.
Quick checks
- Ngan should normally be 0–3 when a measurement is normalized, because 4 Ngan = 1 Rai.
- Square Wah should normally be 0–99 in normalized mixed notation, because 100 Square Wah = 1 Ngan.
- If a source gives larger component values, you can still calculate them; normalize afterward if you want a standard mixed-unit display.