Convert Thai Rai to Acres easily.

If you’ve ever looked at property listings in Thailand or studied Southeast Asian agriculture, you’ve probably seen the term “Rai” pop up. But what does it mean, and how does it compare to acres? Whether you’re a traveler eyeing a vacation home, a farmer analyzing crop yields, or just a curious mind, this guide will turn you into a Rai-to-acre conversion pro. Let’s dig in.

Unit definitions

What is a Thai Rai (rai)?

The Thai Rai is a traditional unit of area used primarily in Thailand. Think of it as Thailand’s version of the acre—it’s deeply rooted in local culture and land management.

• Symbol: rai
• Common uses: Measuring farmland, real estate, and forestry plots.
• Definition: 1 Rai equals 1,600 square meters or 0.16 hectares.

Fun fact: The Rai is part of a trio. It’s made up of 4 Ngan, and each Ngan contains 100 square Wah. If you ever hear someone mention “Wah” in Thailand, they’re talking about a smaller unit—about 4 square meters!

What is an acre (ac)?

The acre is a Western unit with medieval roots, still widely used in the US, UK, and former British colonies.

• Symbol: ac
• Common uses: Agriculture, real estate, and land zoning.
• Definition: 1 acre equals 4,046.86 square meters or about 40% of a hectare.

Here’s a quirky tidbit: An acre was originally defined as the area one man could plow in a day using oxen. Efficiency standards have changed since then, but the measurement stuck!

Conversion formula

Converting Rai to acres is straightforward:
Acres = Rai × 0.3954

For the reverse (acres to Rai):
Rai = Acres ÷ 0.3954

Let’s say you’re looking at a 5-rai rice field in Chiang Mai. Multiply 5 by 0.3954, and you’ll get roughly 1.977 acres. Not too shabby, right?

Example calculations

1. Converting 10 Rai to acres:
   10 rai × 0.3954 = 3.954 acres
   So, a 10-rai farm is about 4 acres—ideal for small-scale crops like orchids or vegetables.
2. Converting 2.5 acres to Rai:
   2.5 acres ÷ 0.3954 ≈ 6.32 rai
   This means 2.5 acres is roughly 6 rai and 1 ngan (since 0.32 rai ≈ 1.28 ngan).

Conversion tables

Thai Rai to Acres

Acres to Thai Rai

Historical background

The Rai’s history is tied to Thailand’s agrarian past. Before metrication, farmers used body parts and daily labor to measure land. A “wah” was the distance of a stretched arm (about 2 meters), and a Rai represented teh area a pair of oxen could plow in a day—similar to the acre’s origin. In 1923, Thailand standardized the Rai to 1,600 square meters, aligning it with metric units while preserving tradition.

Acres, meanwhile, evolved from Roman “ager' (field) to Anglo-Saxon measurements. The 13th-century Statute of Acre standardized it as 4,840 square yards. Today, it’s a bridge between imperial and metric systems, still used in everything from farming to golf courses.

Interesting facts?

1. Size matters: 1 Rai is roughly 0.4 acres—about two-thirds of a soccer field.
2. Cultural anchor: Thai addresses often include Rai for rural properties.
3. Global cousin: Vietnam uses a similar unit called the “cong” (1,000 m²).
4. Metric harmony: 6.25 Rai make 1 hectare.
5. Acre’s cousin: Scotland once used the “Scottish acre,” which was 1.27 English acres.

FAQ