If you have ever watched two people argue over the size of the same plot in Bihar, there is a good chance they were both doing the maths right — and using different Katha sizes. The question "how many Katha in 1 Acre?" has two honest answers in Bihar, and knowing which one your documents use is worth more than any converter. Here is the short version, with the working shown so you can check every number yourself.
Quick answer
- At the Patna/Arrah revenue standard (1 Katha = 3.125 Decimal = 1,361.25 sq ft): 1 Acre = 32 Katha. This is the figure most Bihar converter pages quote, and the one you will usually find in revenue records.
- At the common practical rate used across much of the rest of Bihar (1 Katha = 3.415 Decimal, about 1,487.6 sq ft): 1 Acre = 29.28 Katha.
- 1 Acre = 100 Decimal = 43,560 sq ft in both cases. The acre never changes — only the Katha does.
So when someone says "32 Katha" and someone else says "about 29 Katha," neither is guessing. They are measuring with different Katha.
Acre to Katha conversion table
| Acres | Katha (3.415 rate) | Katha (3.125 rate) |
|---|---|---|
| 0.5 | 14.64 | 16 |
| 1 | 29.28 | 32 |
| 2 | 58.57 | 64 |
| 2.5 | 73.21 | 80 |
| 5 | 146.41 | 160 |
| 10 | 292.83 | 320 |
For everyday conversation, "about 29 Katha" and "32 Katha" are both fine as shorthand — as long as you say which standard you mean before money changes hands.
The formula
An acre is 100 Decimal, so the conversion is simply Decimal divided by the Katha size:
Katha = Acres × 100 ÷ Decimal per Katha
- At 3.415: Katha = Acres × 100 ÷ 3.415 = Acres × 29.28
- At 3.125: Katha = Acres × 100 ÷ 3.125 = Acres × 32
To go the other way: Acres = Katha × Decimal per Katha ÷ 100
So 150 Katha is 150 × 3.415 ÷ 100 = 5.12 Acres at the practical rate, and 150 × 3.125 ÷ 100 = 4.69 Acres at the Patna/Arrah standard. Same 150 Katha on paper, a difference of nearly half an acre on the ground. That gap is exactly why this page exists.
Worked examples
Example 1: Convert 2.5 Acres to Katha. At the 3.415 rate: 2.5 × 29.28 = 73.21 Katha. At the 3.125 rate: 2.5 × 32 = 80 Katha. If a seller quotes the smaller figure and a buyer expects the larger one, the deal is already confused before price is discussed.
Example 2: Convert 64 Katha to Acres. At the 3.125 standard, 64 Katha is exactly 2 Acres (64 ÷ 32). At the 3.415 rate, 64 Katha is 64 × 3.415 ÷ 100 = 2.19 Acres. A round number under one standard is not round under the other — another reason to name your standard in writing.
Example 3: How many Bigha in 1 Acre? Since 1 Bigha = 20 Katha everywhere in Bihar, divide the Katha figure by 20. At the 3.125 standard: 32 ÷ 20 = 1.6 Bigha — the figure quoted in most of Bihar. At the 3.415 rate: 29.28 ÷ 20 = 1.46 Bigha. See the Bigha to Katha guide and the Katha to Square Feet guide.
Why most websites only show 32
Most converter pages present a single number because a single number looks clean. The 32-Katha figure comes from the revenue standard — 1,361.25 sq ft per Katha — which is tidy, official-looking and easy to build a calculator around. But across much of Bihar, everyday buying, selling and measurement practice uses the larger 3.415-Decimal Katha, and our own Katha to Decimal converter uses that practical rate as its default, with the 3.125 standard explained alongside it. Neither standard is "wrong." They are two living systems, and your deed, your district’s practice and your local amin’s measurement decide which one governs your plot. What is wrong is mixing them inside one calculation — converting acres to Katha at 32 and then Katha to square feet at 1,487.6, for example. Pick one standard, use it for every step, and write it down.
Acre in the rest of the Bihar system
For reference, 1 Acre also equals: 100 Decimal (both standards); 43,560 sq ft (both standards); 1.6 Bigha at the 3.125 standard, or 1.46 Bigha at the 3.415 rate; 640 Dhur at the 3.125 standard, or about 585.65 Dhur at the 3.415 rate (20 Dhur per Katha); 0.4047 Hectare (1 Hectare = 2.471 Acres). If your land is recorded in Decimal rather than Katha, see the Decimal to Katha guide; if it is recorded in Dhur, see the Dhur to Decimal guide.
Frequently asked questions
How many Katha are in 1 Acre in Bihar? 32 Katha at the Patna/Arrah revenue standard (3.125 Decimal per Katha), or 29.28 Katha at the common practical rate (3.415 Decimal per Katha).
Why do different websites give different answers? Because they silently use different Katha sizes. A site that uses 1,361.25 sq ft per Katha gets 32; a site that uses about 1,487.6 sq ft gets 29.28. Always check which Katha size a converter uses before trusting its output.
How many Decimal are in 1 Acre? Exactly 100 Decimal. That figure does not change between standards, which is why converting through Decimal is the safest way to move between units.
Is 1 Acre the same in every state? An acre itself is fixed at 43,560 sq ft everywhere. What changes from state to state is the Katha — so "Katha per Acre" changes even though the acre does not.
Which standard should I use for my land? Use the one in your land records and local revenue practice. For Patna and Arrah side documents, expect 3.125 Decimal per Katha; for much of the rest of Bihar, expect 3.415. When money is involved, confirm with the local revenue office before signing.
Bottom line
1 Acre is 100 Decimal, always. In Katha it is 32 at the revenue standard and 29.28 at the practical rate — and the only mistake is using one figure without saying which. Name your standard, convert through Decimal, and check the result against your deed before you agree a price.
