See how your savings or investments can grow over time with compound interest. Adjust the rate, time and contributions to explore different long-term scenarios in USD.
A compound interest calculator estimates how your money can grow over time when interest is added to both your original deposit and the interest you’ve already earned. This “interest on interest” effect is the reason long-term saving and investing can accelerate after enough time passes.
To use this calculator, enter your starting amount, optional monthly contributions, an annual interest rate, and a time period. Then choose how often interest compounds (monthly, daily, etc.) and click Calculate.
The results show your estimated final balance, how much you contributed in total, and how much interest was earned.
Deposit timing assumption: Monthly contributions are modeled as deposits once per month (at the end of each month). Interest is applied according to your selected compounding frequency.
The classic compound interest formula is:
FV = P × (1 + r / n)(n × t)
When you add monthly contributions, each deposit has its own time to compound. That’s why consistent contributions can increase the final value dramatically over long horizons.
A one-time deposit can still grow significantly with time. At 7% annually for 25 years, $10,000 can grow to roughly $54,000+ depending on compounding frequency.
Adding a consistent monthly contribution often matters more than minor differences in compounding frequency. In many scenarios, this can push the final value to $190,000+ over 25 years.
Compounding more frequently means interest is applied more often. That can slightly increase the final balance, but for most people the bigger drivers are time and consistent monthly contributions.
The Rule of 72 estimates how long it takes to double your money: 72 ÷ annual rate (%) ≈ years to double.
At 6%, doubling takes about 12 years (72 ÷ 6 = 12). This is a quick mental shortcut — not an exact forecast — but it helps build intuition.
This calculator shows results in nominal dollars (not inflation-adjusted). Inflation reduces purchasing power over time, so the “real” value of the ending balance may be lower.
To estimate real buying power, compare against an inflation assumption using the Inflation Calculator.
It provides an estimate based on the values you enter. Real-world results may differ due to fees, taxes, changing interest rates, and market performance.
Yes. Contributions are treated as monthly deposits. Compounding frequency controls how interest accrues, but deposits occur monthly in this model.
No. Results are shown in nominal dollars and do not adjust for inflation. Use the Inflation Calculator to estimate real buying power.
For a savings account, use the rate your bank provides. For investments, try a few conservative long-term rates to compare scenarios rather than relying on short-term performance.
More frequent compounding can slightly increase the final balance—especially over long horizons. But time and consistent monthly contributions usually have a bigger effect.
It’s a quick estimate of how long it takes to double your money: 72 divided by your annual rate (in percent) gives an approximate number of years.
Different tools may assume different deposit timing, use APY vs APR, include fees, taxes, or use variable rates. This calculator uses a simplified fixed-rate model for clarity.
Yes. Many credit cards and some loans compound interest, which can cause balances to grow faster than expected. If you want to see how loan payments and total interest work, try the Loan Payment Calculator.
Note: This calculator is for educational purposes only and does not provide financial advice.