How to use the byaj calculator
- Enter the principal — the amount lent or borrowed.
- Choose how the rate is given: ₹ per ₹100 per month (rupaya saikda), % per month or % per year, and enter it.
- Choose between two dates (loan date and repayment date) or enter years, months and days.
- Choose simple interest (sada byaj) or a compound option.
Byaj formula
Simple byaj = Principal × Rate (₹ per 100 per month) ÷ 100 × Months Months = Full months + Extra days ÷ 30 Annual rate = Monthly rate × 12 Compound amount = P × (1 + annual rate ÷ n)^(n × years)
Worked examples
- ₹1,00,000 at ₹2 byaj for 1 year: 1,00,000 × 2 ÷ 100 × 12 = ₹24,000; total ₹1,24,000.
- ₹50,000 at ₹1.5 from 15 Jan 2025 to 20 Mar 2026: 14 months + 5 days = 14.167 months → 50,000 × 1.5 ÷ 100 × 14.167 = ₹10,625.
- ₹20,000 at ₹1 for 1 year 6 months 10 days: 18.333 months → ₹3,666.67.
Byaj rate conversion table
| ₹ per 100 per month | % per year | Monthly byaj on ₹1 lakh | Yearly byaj on ₹1 lakh |
|---|---|---|---|
| ₹0.50 | 6% | ₹500 | ₹6,000 |
| ₹1.00 | 12% | ₹1,000 | ₹12,000 |
| ₹1.50 | 18% | ₹1,500 | ₹18,000 |
| ₹2.00 | 24% | ₹2,000 | ₹24,000 |
| ₹2.50 | 30% | ₹2,500 | ₹30,000 |
| ₹3.00 | 36% | ₹3,000 | ₹36,000 |
Simple vs compound byaj
With simple interest, byaj is charged only on the original amount — the most common arrangement for loans between people, shopkeepers and farmers. With compound interest, unpaid byaj is added to the loan and also earns byaj. Over a long time the difference becomes large: ₹1 lakh at ₹2 per month for 5 years is ₹1,20,000 simple interest, but about ₹1,93,000 if compounded yearly at 24% — the total to repay grows to about ₹2,93,000.
How dates are counted
When you choose “between two dates”, the calculator counts whole months from the loan date — 15 January to 15 February is one month, even though February is short — and then counts the leftover days. Each leftover day is charged as 1/30 of a month, which is how byaj is usually worked out in shops, villages and private lending. If a loan starts on the 31st, the month ends on the last day of shorter months (31 January to 28 February is one month). Banks usually use actual days ÷ 365 instead, so their figure can differ by a few rupees.
Tips when giving or taking a loan
- Write it down. Note the amount, date, rate, and whether interest is simple or compound, and get it signed. A stamped agreement is better.
- Agree how partial payments count — against byaj first or against principal.
- Compare with bank rates. ₹2 per month (24% a year) is much higher than most bank personal loans and gold loans.
- Keep receipts of every repayment.