Converter
Periodic ↔ Annualised Return Converter
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Turn a daily, weekly, monthly, quarterly or half-yearly return into its annualised equivalent — and back again. Also annualises a return earned over any odd holding period, using geometric compounding rather than a naive multiplication.
Which method to use: compounding is the honest answer for an investment return. The simple method exists because Indian EMI schedules divide the quoted annual rate by twelve — use it only when you are reproducing a lender’s amortisation table.
Two Answers, Both Correct — For Different Questions
Ask “what is 12% a year as a monthly rate?” and there are two defensible answers. Which one you want depends entirely on what you are about to do with the number.
The simple method divides by twelve: 12% ÷ 12 = 1.000% per month. This ignores compounding and treats each month as an independent slice of the year.
The effective method asks a stricter question: what monthly rate, compounded twelve times, lands exactly on 12% after a year? That is (1.12)1/12 − 1 = 0.948879% per month. Slightly lower, because the earlier months’ interest earns interest of its own.
The gap looks trivial. It is not. Run the simple 1.000% forward for a year with monthly compounding and you do not get 12% — you get (1.01)12 − 1 = 12.6825%. Sixty-eight basis points appear from nowhere. On a ₹40 lakh balance that is roughly ₹27,000 a year that one of the two numbers is silently hiding.
Which One Your Lender Is Using
Indian lending and deposit products do not agree on a single convention, which is exactly why this conversion matters.
- Home and personal loan EMIs. The standard EMI formula takes the quoted annual rate and divides by twelve. A loan quoted at 8.5% p.a. is amortised at 0.708333% a month, not the effective 0.682149%. Use the simple setting if you are reproducing a bank’s EMI schedule — anything else will not tie out to the paper.
- Credit cards. Card issuers quote a monthly rate. Converting it to an annual rate is where the number becomes uncomfortable: 3.5% a month is not 42% a year, it is (1.035)12 − 1 = 51.11%. Even a comparatively mild 2% a month is 26.82% effective.
- Fixed deposits. Banks compound quarterly. A 7% p.a. FD is really (1 + 0.07/4)4 − 1 = 7.1859% effective. The same 7% compounded monthly would be 7.2290%, and daily 7.2501%. The headline rate is identical; the money is not.
- Comparing anything against anything. Convert both sides to an effective annual rate first. It is the only basis on which a quarterly-compounded FD, a monthly-compounded recurring deposit and a flat-rate consumer loan can be honestly ranked.
The Formulas, Written Out
Simple annual = monthly × 12
Effective monthly = (1 + annual)1/12 − 1
Effective annual = (1 + monthly)12 − 1
Worked: 12% p.a. → (1.12)1/12 − 1 = 0.948879% per month
Worked: 1% p.m. → (1.01)12 − 1 = 12.6825% per year
Three Mistakes Worth Avoiding
Multiplying a card rate by twelve. It understates the real cost by nine percentage points or more. The compounding is not optional — unpaid interest is added to the balance and charged again next cycle.
Comparing a flat rate to a reducing rate. A “10% flat” consumer loan is not comparable to 10% reducing; the effective cost is close to double, because flat interest is charged on the original principal for the whole tenure even as you repay it. Convert first with the flat to reducing rate converter.
Assuming the quoted rate is the earned rate. On deposits the compounding frequency decides the difference between the number on the poster and the number in your account. Always convert to an effective annual rate before deciding.
Where to Go Next
Once you have the rate on the right basis, put it to work: the EMI calculator turns a loan rate into a monthly instalment, the FD calculator applies quarterly compounding to a deposit, the compound interest calculator projects a corpus forward, and the compound interest converter handles frequencies beyond monthly — quarterly, daily and continuous. For a wider view of borrowing cost, the floating versus fixed home loan comparison and the personal loan versus credit card EMI comparison put competing structures side by side.
Frequently Asked Questions
How do I convert a monthly interest rate to annual?
For simple interest, multiply the monthly rate by 12. For compound interest, use the formula: Annual Rate = (1 + monthly rate)^12 − 1. This tool does both conversions automatically.
What is the effective annual rate (EAR)?
EAR accounts for compounding within a year. For example, a 1% monthly rate compounded monthly gives an EAR of about 12.68% — not 12%. Our tool calculates EAR accurately.
Do banks in India quote flat or reducing rates?
RBI mandates that banks quote interest rates on an Effective Annual Rate (EAR) basis for transparency. However, many NBFCs and fintech lenders still quote flat rates. Use our Flat to Reducing Rate Converter to compare.
Can I convert a daily, quarterly or continuous rate here?
No — this tool converts between annual and monthly only. For quarterly, semi-annual, daily and continuous compounding, use the compound interest converter, which handles every frequency and reports the effective annual rate for each.
Which setting should I use for a home loan EMI?
Simple. Banks amortise EMIs on the quoted annual rate divided by twelve, so 8.5% p.a. becomes 0.708333% per month. The effective figure (0.682149%) is the more honest measure of the rate, but it will not reproduce your bank’s schedule.
Why is my credit card’s annual rate so much higher than 12 × the monthly rate?
Because unpaid interest is added to the balance and charged again the following cycle. At 3.5% per month the effective annual rate is (1.035)^12 − 1 = 51.11%, not 42%.