Convert rai to square metres in Thailand
Expat buyers need reliable conversions between traditional Thai units and square metres. The fixed ratios are: 1 rai = 1,600 sq m, 1 ngan = 400 sq m, 1 sq wah = 4 sq m. Wrong conversions at contract stage create legal disputes over price and boundaries.
At Thai Visa Centre in Bangkok, we help expats align immigration, banking, and property plans. Start with our buying property overview, review rai and ngan basics, or browse the full property hub.
Standard conversion used on land listings and due diligence reviews.
Quarter rai. Useful for mid-size house plots.
Base unit. Multiply square wah by four for square metres.
Traditional and metric conversions must stay consistent.
Rai to square metre conversion table
Use this table when reviewing land listings, chanote deeds, and sale agreements. Square feet figures are approximate for readers familiar with imperial measure.
| Thai unit | Square wah | Square metres | Square feet (approx.) |
|---|---|---|---|
| 1 rai | 400 sq wah | 1,600 sq m | ~17,222 sq ft |
| 1 ngan | 100 sq wah | 400 sq m | ~4,306 sq ft |
| 1 sq wah | 1 sq wah | 4 sq m | ~43 sq ft |
| 0.5 rai | 200 sq wah | 800 sq m | ~8,611 sq ft |
| 2 rai | 800 sq wah | 3,200 sq m | ~34,445 sq ft |
| 1-2-50 notation | 450 sq wah | 1,800 sq m | ~19,375 sq ft |
Practical conversion examples
Real listing formats expats encounter. Always verify the chanote figure matches before signing.
| Listing example | Calculation | Note |
|---|---|---|
| Bangkok townhouse plot: 50 sq wah | 50 x 4 = 200 sq m | Common urban lot size. Verify against chanote. |
| Chiang Mai house plot: 1 ngan | 400 sq m | Quarter rai suburban plot. |
| Phuket villa land: 2 rai | 2 x 1,600 = 3,200 sq m | Resort-area leasehold plots often quoted in rai. |
| Agricultural land: 10 rai | 10 x 1,600 = 16,000 sq m | Large rural holdings. Confirm deed category supports intended use. |
Four-step conversion method
Use this workflow during due diligence to cross-check agent marketing against the official title deed.
Read the chanote in rai-ngan-wah
Start from the official deed notation, for example 1-2-50 means 1 rai, 2 ngan, 50 sq wah.
Convert to total square wah
Multiply rai by 400, ngan by 100, then add sq wah. Example: 1-2-50 = 400 + 200 + 50 = 450 sq wah.
Multiply by 4 for square metres
Each square wah equals 4 sq m. 450 sq wah x 4 = 1,800 sq m.
Compare to listing and contract
Any mismatch between deed, survey, and sale agreement area is a red flag for your lawyer to investigate.
Common conversion mistakes
These errors appear in contracts and cause disputes after transfer. Catch them before you pay a deposit.
- Confusing linear wah (2 metres length) with square wah (4 sq metres area). They are different measures.
- Using rounded conversions like 1 rai = 1,600 sq m but then dividing incorrectly for fractional plots.
- Trusting agent square metre figures without cross-checking chanote rai-ngan-wah notation.
- Mixing imperial acres with Thai rai without conversion. One rai is not one acre.
- Signing contracts where listed area in sq m does not match title deed traditional units.
Contract area clause: Insist the sale agreement states area in both traditional units and square metres matching the chanote. A discrepancy gives you grounds to renegotiate or withdraw before transfer.
Common mistakes
Expat buyers and long-stay residents encounter these errors when converting Thai land units to square metres. Verify your facts with licensed counsel before signing or paying a deposit.
- Using rounded metric conversion without verifying chanote traditional unit source figure
- Comparing international listings in sqm against Thai deed area in rai only
- Assuming developer marketing sqm includes balcony or common area without deed split
- Skipping lawyer cross-check when agent quotes sqm but deed shows ngan and sq wah
- Budgeting land tax using converted sqm without Revenue Department appraisal schedule
Frequently asked questions
General answers on rai to square metre conversion for expat property buyers. This is orientation, not legal advice for your specific transaction.
Q:How many square metres in 1 rai?
One rai equals 1,600 square metres. That also equals 4 ngan or 400 square wah. This is the standard conversion on Thai land documents and listings.
Q:How many square metres in 1 ngan?
One ngan equals 400 square metres, or 100 square wah, or one quarter of a rai.
Q:How many square metres in 1 square wah?
One square wah equals 4 square metres. Multiply any square wah figure by 4 to get square metres.
Q:How do I convert 1-2-50 to square metres?
Convert to square wah first: 1 rai (400) + 2 ngan (200) + 50 sq wah = 450 sq wah. Then multiply by 4: 450 x 4 = 1,800 square metres.
Q:Why do conversion errors matter legally?
Area affects price, tax base, and boundary disputes. Signing a contract with wrong square metre figures can mean overpaying or buying less land than you believed you purchased.
Q:Do title deeds show square metres?
Chanote deeds primarily record traditional rai-ngan-wah units. Some marketing materials add square metre conversions. Always verify against the original deed during due diligence.
Q:Does this guide replace a property lawyer?
No. Conversion is one checkpoint in title search. Your lawyer confirms deed area, survey boundaries, and contract figures match before you pay a deposit.
Q:Where should I start reading?
Begin with our buying property overview, then the due diligence checklist, then contact a lawyer before paying any deposit.