Bihar’s land maths has one comforting constant: 1 Bigha is always 20 Katha. The confusion starts one step later, when that Bigha has to become Decimal — because a Katha is not the same size in every Bihar record. This guide gives you both standards, the tables and the worked examples, so you never have to guess which Decimal figure belongs to your plot.
Quick answer
- 1 Bigha = 20 Katha (everywhere in Bihar)
- At the common practical rate (1 Katha = 3.415 Decimal): 1 Bigha = 68.3 Decimal ≈ 29,751 sq ft ≈ 0.683 Acre
- At the Patna/Arrah revenue standard (1 Katha = 3.125 Decimal = 1,361.25 sq ft): 1 Bigha = 62.5 Decimal = 27,225 sq ft = 0.625 Acre
- 1 Bigha = 400 Dhur in both cases, because Dhur counts Katha, not square feet.
The Katha count never changes. Only the area each Katha represents does — and that is the whole story of Bihar land conversion.
Bigha to Decimal conversion table
| Bigha | Katha | Decimal (3.415 rate) | Decimal (3.125 rate) | Sq ft (3.415 rate) | Sq ft (3.125 rate) |
|---|---|---|---|---|---|
| 0.5 | 10 | 34.15 | 31.25 | 14,876 | 13,613 |
| 1 | 20 | 68.3 | 62.5 | 29,751 | 27,225 |
| 2 | 40 | 136.6 | 125 | 59,503 | 54,450 |
| 3 | 60 | 204.9 | 187.5 | 89,254 | 81,675 |
| 5 | 100 | 341.5 | 312.5 | 148,757 | 136,125 |
| 10 | 200 | 683 | 625 | 297,515 | 272,250 |
Square-feet figures at the 3.415 rate use 1 Katha ≈ 1,487.6 sq ft (3.415 × 435.6 sq ft per Decimal), rounded to the nearest square foot.
The formula
Decimal = Bigha × 20 × Decimal per Katha
- At 3.415: Decimal = Bigha × 68.3
- At 3.125: Decimal = Bigha × 62.5
To go the other way: Bigha = Decimal ÷ 68.3 (practical rate) or Decimal ÷ 62.5 (revenue standard). See the Bigha to Katha guide; the Decimal to Katha guide; and the Katha to Square Feet guide.
Worked examples
Example 1: Convert 3.5 Bigha to Decimal. At the practical rate: 3.5 × 68.3 = 239.05 Decimal. At the revenue standard: 3.5 × 62.5 = 218.75 Decimal. A gap of more than 20 Decimal on a single modest holding — and both answers are "correct" under their own standard.
Example 2: Convert 125 Katha to Bigha. 125 ÷ 20 = 6.25 Bigha — in everyday language, 6 Bigha and 5 Katha. That Bigha figure is the same under both standards; only its Decimal and square-feet values differ (6.25 × 68.3 = 426.88 Decimal, or 6.25 × 62.5 = 390.63 Decimal).
Example 3: A plot listed as 100 Decimal — how many Bigha is that? At the practical rate: 100 ÷ 68.3 = 1.46 Bigha. At the revenue standard: 100 ÷ 62.5 = 1.6 Bigha. This is the same 1.6 figure you will hear quoted all over Bihar — it quietly assumes the 3.125 standard. If your documents use the practical rate, 100 Decimal is closer to one-and-a-half Bigha than to 1.6.
Why two standards exist
A Bigha is always 20 Katha, but a Katha itself is defined differently in different records. The Patna/Arrah revenue tradition fixes 1 Katha at 1,361.25 square feet — exactly 3.125 Decimal. Much of the rest of Bihar, in everyday buying, selling and measurement practice, uses a larger Katha of 3.415 Decimal (about 1,487.6 square feet). Multiply either Katha by 20 and you get a Bigha — but the two Bighas differ by about 2,526 square feet. Neither side is wrong. They are two living standards, 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 Bigha to Katha at 20 and then Katha to Decimal at the wrong rate for your district. Pick one standard, use it for every step, and write it down.
Bigha, Decimal and Acre together
Because 1 Acre = 100 Decimal, the Bigha-to-Acre figures follow directly: At the 3.415 rate, 1 Bigha = 0.683 Acre, so 1 Acre ≈ 1.46 Bigha. At the 3.125 rate, 1 Bigha = 0.625 Acre, so 1 Acre = 1.6 Bigha. See the Acre to Katha guide and the Dhur to Decimal guide.
Frequently asked questions
How many Decimal are in 1 Bigha in Bihar? 68.3 Decimal at the common practical rate (3.415 per Katha), or 62.5 Decimal at the Patna/Arrah revenue standard (3.125 per Katha).
How many Katha are in 1 Bigha? Exactly 20 Katha, under both standards.
How many square feet are in 1 Bigha in Bihar? About 29,751 sq ft at the practical rate, or 27,225 sq ft at the revenue standard.
How many Dhur are in 1 Bigha? 400 Dhur — 20 Katha × 20 Dhur per Katha. This does not change between standards.
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 Bigha is 20 Katha, always. In Decimal it is 68.3 at the practical rate and 62.5 at the revenue standard — and the only real mistake is quoting a Decimal figure without saying which Katha sits behind it. Name your standard, convert through Katha, and check the result against your deed.
