Compound Interest Calculator
See how your money grows when interest compounds over time.
Calculator
1 = yearly, 4 = quarterly, 12 = monthly, 52 = weekly, 365 = daily.
Example Result
Your result will appear here
The calculated result will appear here after you press Calculate.
Estimates for planning only; not financial, tax or investment advice. See our Disclaimer.
Watch: Compound Interest Explained: The Formula, a Worked Example and the APY Mistake
5:22 · Plays in YouTube’s privacy-enhanced player; nothing loads from YouTube until you press play. Watch on YouTube
About the Compound Interest Calculator
This calculator shows what one deposit grows to when interest is added to the balance and then earns interest too. Enter the starting amount, the annual rate, the time in years and how many times a year interest is added. It suits savings accounts, certificates of deposit and any balance left alone at a fixed rate. It does not handle regular deposits or withdrawals, and it does not account for tax, fees or inflation.
How to Use the Compound Interest Calculator
- 1
Enter your starting principal amount.
- 2
Enter the annual interest rate and how many years it will grow.
- 3
Enter how many times a year interest compounds, then press Calculate.
Compound Interest Calculator Examples
By O.E. — Partner, chairman of the board and CEO of a metal products manufacturer for 21 years; the company exports to 45 countries.
Drafted with AI assistance; calculations checked against primary sources and tested with the site's own code. About FlowUtil
Last reviewed
What the calculator does with your four numbers
The calculator uses one formula: A = P × (1 + r/n)^(n×t). The rate you enter as a percentage is divided by 100 and then by n to give the rate for each period, so 6% compounded monthly is 0.06 ÷ 12 = 0.005 a month. The exponent n × t is the number of periods: 12 a year for 10 years is 120.
Interest earned is the future value minus the principal. The model is one deposit left alone: nothing is added or taken out, and each period's interest stays in the balance. For why the balance curves upward and how this differs from simple interest, read what compound interest is.
| Symbol | Meaning |
|---|---|
| A | Future value (principal + all compounded interest) |
| P | Principal — the initial lump sum |
| r | Annual interest rate, entered as a percentage (e.g. 6 for 6%) |
| n | Compounding periods per year (1 = annual, 12 = monthly, 52 = weekly, 365 = daily) |
| t | Time horizon in years |
Three deposits, worked through
1Principal $10,000, 6% annual rate, 10 years, compounded monthly (n = 12).
A = 10,000 × (1 + 0.06/12)^(12×10) = 10,000 × 1.005^120
A = $18,193.97 · Interest = $8,193.97
The same 6% compounded once a year gives $17,908.48, so monthly compounding is worth $285.49 over the decade at the same stated rate.
2Principal $5,000, 4% annual rate, 20 years, compounded annually (n = 1).
A = 5,000 × (1 + 0.04/1)^(1×20) = 5,000 × 1.04^20
A = $10,955.62 · Interest = $5,955.62
The balance a little more than doubles. With annual compounding, the rate for each period is the full 4%.
3Principal $25,000, 8% annual rate, 30 years, compounded daily (n = 365).
A = 25,000 × (1 + 0.08/365)^(365×30)
A = $275,506.95 · Interest = $250,506.95
The interest is ten times the deposit. At 4% instead of 8%, the same deposit reaches $82,997.47, so halving the rate cuts the interest by more than three-quarters.
APY or nominal rate: which number goes in the rate field
The rate field takes a nominal annual rate, the rate before compounding. US banks quote deposit accounts as an APY under Regulation DD, and an APY already includes compounding over a year. Typing an APY and then choosing monthly compounding counts the compounding twice.
If all you have is an APY, enter it with compounds per year = 1. A 4.00% APY on $10,000 for 5 years gives $12,166.53. The same account written as a nominal rate is 3.9285% compounded monthly, which gives $12,166.54; the extra cent is rounding in the rate.
APY = (1 + r/n)^n − 1
r = n × ((1 + APY)^(1/n) − 1)
So 6% compounded monthly is an APY of 6.17%.
What to enter for compounds per year
Use the frequency in the account terms, as a whole number. If you leave the field empty, the calculator uses 12. This is $10,000 at 6% for 10 years:
| Compounding | Enter | Future value | More than yearly |
|---|---|---|---|
| Yearly | 1 | $17,908.48 | n/a |
| Quarterly | 4 | $18,140.18 | $231.70 |
| Monthly | 12 | $18,193.97 | $285.49 |
| Weekly | 52 | $18,214.89 | $306.41 |
| Daily | 365 | $18,220.29 | $311.81 |
Most of the gain arrives by monthly. Going from monthly to daily adds $26.32 over the 10 years. Raising the rate from 6% to 6.25% at monthly compounding adds $458.21, so when you compare accounts the rate usually matters more than the schedule.
Reading the future value
The future value is the balance at the end of the term, in that year's dollars. It assumes the rate you entered is earned in every period, with no withdrawals, tax or fees. Interest earned is the part of the balance that did not come from your deposit.
Prices rise over the same years. At 3% inflation, $18,193.97 in 10 years buys what $13,538.02 buys today, which you can check with the inflation calculator. A 6% return with 3% inflation is a real return of about 2.9%, because 1.06 ÷ 1.03 − 1 = 0.0291.
To check a result in your head, the Rule of 72 divides 72 by the rate. At 6% a balance doubles in about 12 years, so about $18,000 after 10 years is the right size.
Tax on interest in a taxable account
In the US, interest is generally taxable in the year it becomes available to you, even if you leave it in the account. A taxable balance therefore compounds on what is left after tax.
For a rough figure, enter the rate after tax. At a 24% marginal federal rate, 6% becomes 6 × (1 − 0.24) = 4.56%, and $10,000 over 10 years with monthly compounding reaches $15,763.87 instead of $18,193.97. State tax changes the figure, and retirement accounts such as a 401(k) or IRA generally defer or remove that yearly tax. This is an estimate, not tax advice.
Running the same formula on debt
The arithmetic also shows what an unpaid balance costs. $2,000 on a card at a 22% APR, compounded daily with no payments and no new purchases, grows to $3,105.00 in two years. Real cards require minimum payments and add fees, so read this as the size of the cost, not as a statement.
A loan with a fixed monthly payment shrinks instead of grows. For those, use the loan amortization calculator.
When another calculator fits better
- Regular deposits: the savings goal calculator adds a monthly amount to the balance.
- Growth that has already happened: the CAGR calculator turns a start value and an end value into an annual rate.
What the projection leaves out
- A changing rateThe rate stays fixed for the whole term. Savings rates and market returns move, and market returns can be negative.
- Deposits and withdrawalsOnly the starting amount earns interest. Nothing is added or taken out.
- Tax and feesIncome tax, account fees and fund expense ratios are not deducted.
- InflationResults are in nominal dollars.
Three entry errors that change the answer
- Typing the rate as a decimalEnter 6 for 6%. Entering 0.06 means 0.06%, and $10,000 for 10 years then shows $10,060.18 instead of $18,193.97.
- Putting months in the years fieldTime is in years, so 18 months is 1.5. Compounds per year is a yearly count, not the total number of periods.
- Counting compounding twiceAn APY already includes compounding. Enter it with compounds per year = 1.
Sources
- Consumer Financial Protection Bureau, Regulation DD, 12 CFR 1030.2, definition of annual percentage yield.
- 12 CFR Part 1030, Appendix A, Annual Percentage Yield Calculation.
- Consumer Financial Protection Bureau, What is a "daily periodic rate" on a credit card?
- Internal Revenue Service, Topic no. 403, Interest received.