How to use the compound interest calculator
- Starting balance: Money invested at the beginning.
- Monthly deposit: Amount added at the end of each month.
- Annual interest rate (%): Assumed nominal annual return, not a guaranteed rate.
- Months: How many complete months to project.
- Select Calculate to see the result. Change any input and calculate again to compare.
Worked example
1,000 plus 100 monthly at 5% for 12 months grows to approximately 2,279.05.
Formula and assumptions
Starting balance + deposits + growth.
Assumes a constant rate and monthly compounding. Excludes fees, taxes and inflation. Returns are hypothetical.
Reference: Investor.gov compound interest
Common questions
Why might my result differ from another estimate?
Assumes a constant rate and monthly compounding. Excludes fees, taxes and inflation. Returns are hypothetical. Keep the same inputs and rounding when comparing tools.
Are my entries saved?
No. Calculations run on your device. Reloading or closing this page may clear your entries.