Assuming steady returns
Markets and rates do not move in a straight line. A fixed return is only a planning shortcut.
Savings calculator
Compound Interest Calculator
Estimate how an initial balance and regular monthly contributions could grow over time. This calculator is educational and uses a simplified compound growth model.
Updated: June 10, 2026
Calculate future value
Future value—
Total contributions—
Estimated growth—
Live scenario comparison
Conservative return—
Current inputs—
+$50 monthly contribution—
Growth breakdown insight
This insight updates to compare deposits with estimated growth.
Total contributions—
Estimated growth—
How the calculation works
The calculator compounds the starting balance monthly and adds monthly contributions at the end of each month. This is a simplified model for education and planning.
Future value = starting balance grown monthly + each contribution grown for the remaining months
Worked example
If you start with $5,000, add $250 per month, and estimate a 6% annual return for 10 years, the simplified future value is about $50,100 when contributions are added at the end of each month. About $35,000 comes from your starting balance and contributions, while the rest is estimated growth.
Common mistakes
Ignoring inflation
A future dollar may buy less than a dollar today. Consider real purchasing power.
Forgetting fees and taxes
Account fees, fund expenses, and taxes can reduce actual results.
How to read the result
Future value is the estimated ending balance. Total contributions combines the starting balance and all monthly additions. Estimated growth is the difference between those two numbers, before any taxes, fees, or inflation adjustment.
Next steps
Test conservative, moderate, and optimistic return assumptions rather than relying on one number. For a specific target, use the savings goal calculator. To compare savings-account yields, use the APY comparison calculator.
FAQ
Is compound interest guaranteed?
No. Savings accounts may have stated rates, while investments can rise or fall. This calculator is only an estimate.
Does the calculator include taxes?
No. Taxes and fees are not included because they vary by country, account type, and personal situation.
Why are monthly contributions important?
Regular contributions increase the amount that can compound and may reduce reliance on one large starting balance.
How to read this estimate
The result is an educational estimate based only on the inputs shown on this page. It is useful for comparing assumptions, spotting cost drivers, and understanding the formula, but it is not a recommendation or a guarantee.
Before using a result for a real decision, compare it with official documents, local rules, fees, taxes, insurance, and any professional guidance that applies. See How We Calculate and the Disclaimer for more context.
Scenario comparison
Compound growth estimates become more useful when you run a conservative, baseline, and higher-contribution scenario. The conservative case can use a lower return or shorter contribution period. The baseline can use your current habit. The higher-contribution case shows what happens if you increase monthly deposits instead of raising the assumed return.
Try changing only one input at a time. If you raise both the return and the contribution, it becomes hard to see which assumption created the difference. For long horizons, contribution consistency and time often matter more than a small change in the starting balance.
Conservative
Lower the assumed return and keep contributions realistic. This helps avoid building a plan around an optimistic number.
Baseline
Use the amount you can contribute consistently without relying on irregular income.
Contribution boost
Increase the monthly contribution and compare the added deposits with the change in estimated growth.
Result quality checklist
- The annual return is an educational assumption, not a guaranteed rate or investment forecast.
- Taxes, fees, and inflation are considered separately before treating the future value as purchasing power.
- The time horizon matches the goal, not just a round number that makes the result look larger.
- Monthly contributions are sustainable enough to continue through normal budget changes.
Before you rely on the number
Use the calculator as a comparison tool rather than a final answer. The most helpful result is usually the direction of change: which input moves the outcome most, which assumption creates the biggest risk, and whether the monthly cash flow still feels realistic after normal life expenses. Save or write down the inputs used for each scenario so you can compare them consistently later.
Any simplified calculator leaves out details that can matter in real accounts, contracts, tax rules, and local markets. If a result will influence a major purchase, loan, payoff plan, savings target, or household budget, compare it with official documents and independent estimates. Treat surprising results as a prompt to check the inputs first, then review the assumptions behind the formula.
Related calculators
Use the savings goal calculator when you have a target amount, the APY comparison calculator for deposit-rate comparisons, and the inflation calculator to think about future purchasing power.