Convert square metres to Talang Wah (ตร.วา)

A traditional unit fixed by statute

The wah began as a body measure, the span of a man's outstretched arms, and would have drifted like every other anthropometric unit had Siam not legislated it. Metrication under the Weights and Measures Act fixed the wah at exactly 2 metres, and everything above it in the Thai land system inherits that exactness.

That single decision is why Thai land arithmetic is unusually clean: 1 tarang wah = 4 m², 1 ngan = 100 tarang wah = 400 m², and 1 rai = 4 ngan = 1,600 m². No district variants, no revenue-manual archaeology, no reconstructed values.

How Thai property is quoted

Chanote title deeds state area as rai-ngan-wah, read positionally: "2-1-35" is two rai, one ngan and thirty-five square wah, which is 3,740 m². As with the South Asian systems, reading the string as a decimal produces a badly wrong area, and it is the single most common mistake foreign buyers make.

Bangkok condominium and townhouse land is priced per tarang wah, upcountry agricultural land per rai. A listing that switches units is usually signalling a switch in market type, and comparing a per-wah city price with a per-rai provincial price requires normalising to square metres first.

The linear wah still matters

Beyond area, the wah survives as a length in construction and canal work, and the sen (20 wah, 40 m) appears in older cadastral and irrigation records. Both are exact multiples of the metre, so historical Thai survey data converts without the uncertainty that plagues comparable South Asian records.

Below the wah sit the sok (cubit, 0.5 m), khuep (span, 0.25 m) and niu (finger, 0.02083 m), all similarly fixed by the metrication statute. They appear in traditional architecture and boat-building specifications more than in land documents.

Using Thai figures with confidence

Because the system is exact, a conversion error in Thai land data is almost always a parsing error rather than a factor error: a rai-ngan-wah string misread, or ngan and wah transposed. Validate by converting back to the three-part form and comparing with the deed.

For due diligence, note that the Land Department's surveyed area on the chanote governs, and that older Nor Sor 3 and Nor Sor 3 Gor documents carry less precise boundaries even though their areas are stated in the same units. The unit is exact; the survey behind an individual document may not be.

Length, area and the metric fix

The wah is a length of exactly two metres, fixed at that value when Thailand metricated, and the square wah of exactly four square metres is the area unit derived from it. Both appear in property documents, and translated listings routinely drop the word 'square', which changes the meaning of the figure entirely.

The two-metre value has an ergonomic origin: the wah was the span of a man's outstretched arms, and it was rounded to a clean metric figure rather than preserved as a measured average. That decision is why the whole Thai land ladder — wah, ngan, rai — converts exactly, and it is the reason Thai title deeds can be read directly against a metric survey without reconciliation.

Common mistakes to avoid

• Rai-ngan-wah strings such as "2-1-35" are positional, not decimal — that plot is 3,740 m², not 2.135 rai.
• Tarang wah (4 m²) is the area unit; the bare wah (2 m) is a length, and listings sometimes omit "tarang".
• Chanote areas are surveyed; Nor Sor 3 areas use the same units but weaker boundary evidence.

Questions people ask about the Talang Wah (ตร.วา)

How many square metres is one tarang wah?

Exactly 4 m², because the wah is fixed at exactly 2 metres by Thai statute. One hundred tarang wah make a ngan (400 m²), and four ngan make a rai (1,600 m²).

How do I read a Thai title deed area like "1-2-50"?

Positionally: one rai, two ngan, fifty square wah — that is 1,600 + 800 + 200 = 2,600 m². It is not one point two five rai.

Is the Thai wah the same everywhere in Thailand?

Yes. Unlike most traditional units in this atlas, the wah was standardised nationally against the metre, so there are no provincial variants to check.