Compound Interest Calculator: Yearly, Monthly or Daily

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Quick answer

Enter a principal, an annual rate, a number of years and how often interest compounds (yearly, quarterly, monthly or daily). The calculator returns the maturity value and the interest earned using A = P(1 + r/n)^(nt). ₹1,00,000 at 8% for 10 years, compounded monthly, grows to about ₹2,21,964, of which roughly ₹1,21,964 is interest. The sum is worked out in your browser as you type.

What the Compound Interest Calculator does

Put in a principal, an annual rate and the number of years, then pick a compounding frequency: yearly, quarterly, monthly (the default) or daily. The tool shows the maturity value, the interest earned and your original principal, and recalculates whenever you change a field. Figures are in rupees.

Compounding means interest on interest. With simple interest only the principal earns. Here each period's interest joins the balance and earns interest itself, so the total curves upward, and more frequent compounding ends a little higher.

How it works

It applies the standard compound interest formula: A = P(1 + r/n) raised to the power n × t. P is the principal, r the annual rate as a decimal, n the number of compounds per year and t the years.

The maturity value is A, and the interest earned is A minus the principal. The frequency sets n (1 for yearly, 4 for quarterly, 12 for monthly, 365 for daily), and a larger n pushes the result up slightly.

Methodology

Step 1. Take the principal P, the annual rate r (as a percentage), the years t, and the compounds per year n (1, 4, 12 or 365).
Step 2. Apply A = P × (1 + r/n) to the power of (n × t).
Step 3. Report the maturity value A and the interest earned, which is A − P.
Step 4. Recompute whenever an input changes.

Compound interest

A = P × (1 + r/n)^(n × t)
P = principal, r = annual rate (decimal), n = compounds per year, t = years
Interest earned = A − P

Worked examples
₹1,00,000 at 8%, 10 years, compounded monthly (n = 12): A ≈ ₹2,21,964 (interest ≈ ₹1,21,964)
Same deposit compounded yearly (n = 1): ₹2,15,893, which is less because it compounds less often

Frequency matters: the same ₹1,00,000 at 8% over 10 years yields about ₹2,15,893 yearly, ₹2,20,804 quarterly, ₹2,21,964 monthly and ₹2,22,535 daily. The default here is monthly.

Assumptions

One fixed annual rate for the whole term. Real rates change.
A single lump sum with nothing added or withdrawn (for regular monthly investing, use the SIP calculator).
Each period's interest is reinvested at the same rate, which is what makes it compound.
The figure is gross. Tax on interest, fees and inflation are not deducted.

Technical details

Inputs	Principal, annual rate %, years, frequency
Frequencies	Yearly, quarterly, monthly (default), daily
Outputs	Maturity value, interest earned, principal
Currency	Rupees (₹)
Formula	A = P(1 + r/n)^(nt)
Where it runs	In your browser, updating as you type

Standards and references

A = P(1 + r/n)^(nt): the standard compound interest formula, which counts interest on both the principal and the interest already added.
Compounding frequency (n): yearly (1), quarterly (4), monthly (12) or daily (365). A higher n gives a slightly higher maturity value.
Rule of 72: a quick mental check: money roughly doubles in 72 ÷ rate years, so about 9 years at 8%.

Accuracy and limits

It assumes a constant rate and full reinvestment. A real account whose rate changes, or one you withdraw from, will end up somewhere else.

The result is gross. Tax on the interest, account fees and inflation are not deducted, so the money you can actually spend is lower.

Daily compounding uses n = 365. It does not model leap years or the 360-day convention some institutions use.

It handles a one-time deposit only. For a recurring monthly amount, use the SIP calculator for investments or the RD calculator for bank deposits.

Real-world uses

Project a lump sum

See what a one-time deposit could grow to over a chosen term.

Compare frequencies

Check how much yearly, quarterly, monthly or daily compounding changes the outcome.

Long-term savings

Estimate how a sum compounds over 10, 20 or 30 years.

Understand compounding

Watch interest on interest pull ahead of flat interest as you raise the years.

When it fits, and when it doesn't

Good for

Growth of a one-time lump sum
Comparing compounding frequencies
Long-term savings projections
Learning how compounding works

Not the best choice for

Regular monthly contributions
Loans and EMIs
After-tax or inflation-adjusted figures

Investing a fixed amount every month? Use the SIP calculator. For a bank fixed deposit, the FD calculator uses quarterly compounding. For borrowing, use the loan or EMI calculator.

Frequently asked questions

What is the compound interest formula?

A = P(1 + r/n) to the power of (n × t). P is the principal, r the annual rate as a decimal, n the compounds per year and t the years. The interest earned is A minus P.

How does compounding frequency change the result?

More frequent compounding earns slightly more, because interest joins the balance sooner and starts earning too. On ₹1,00,000 at 8% over 10 years the maturity rises from about ₹2,15,893 with yearly compounding to ₹2,22,535 with daily.

How is compound interest different from simple interest?

Simple interest is charged only on the original principal, so it grows in a straight line. Compound interest is charged on the principal plus the interest already added, so it grows exponentially and pulls ahead over time.

Which frequency should I choose?

Match your account. Savings accounts often compound daily or monthly, and many fixed deposits compound quarterly. The tool defaults to monthly.

Does it deduct tax?

No. The maturity shown is gross. Interest is usually taxable, so your return after tax and any fees is lower.

Can I use it for a monthly investment?

No, it models a single lump sum. For a fixed amount invested every month, use the SIP calculator, which handles recurring contributions.

What is the rule of 72?

A shortcut for how long money takes to double: divide 72 by the rate. At 8% that is about 9 years, and the calculator shows a lump sum roughly doubling over that span.

Does daily compounding handle leap years?

It uses 365 days a year for simplicity, so it does not adjust for leap years or for the 360-day basis some institutions apply.

Is the interest rate fixed?

Yes. The calculation assumes one constant rate for the whole term. If your real rate changes, the actual result will differ.

What about continuous compounding?

That is the theoretical limit, A = P times e to the power of (r × t). This tool goes from yearly up to daily, and daily lands close to the continuous figure anyway.

Why does my bank fixed deposit show a different number?

Indian banks usually compound FDs quarterly and deduct tax. The FD calculator fixes quarterly compounding and will match your bank more closely.

What currency does it use?

It shows rupees, but the maths does not depend on currency. The same percentages and periods apply to any currency.

References

The result comes from A = P(1 + r/n)^(nt) at the frequency you pick (monthly unless you change it). It is a gross figure that assumes a fixed rate and full reinvestment, before tax or inflation.

Simple Interest Calculator

Work out flat simple interest, charged only on the principal and never on earlier interest. In ₹, calculated in your browser as you type.