Compound Interest Calculator (Annual, Quarterly, Monthly, Daily)
See how a starting balance plus monthly contributions grow over time. Pick annual, quarterly, monthly, or daily compounding to match how your account credits interest. Monthly contributions are treated as end-of-month deposits.
Inputs
Results
- Future value
- $280,657.02
- Total contributions
- $125,000.00
- Interest earned
- $155,657.02
- Growth multiple
- 2.25×
Includes inputs, results, and schedule.
The compound interest formula
Future value = P × (1 + r/n)^(n·t) + PMT × [((1 + r/n)^(n·t) − 1) / (r/n)], where P is the starting principal, PMT is the periodic contribution, r is the annual rate, n is compounding periods per year, and t is years.
Why time matters more than rate
Starting early has an outsized impact. A saver who invests $500/month from age 25 to 35 and then stops usually ends up with more than a saver who invests $500/month from age 35 to 65 — because the first saver's balance compounds for 30 extra years.
Frequently asked questions
Which compounding frequency should I pick?
Match it to your account: most high-yield savings and CDs compound daily, mutual funds/brokerage sweep accounts compound monthly, and some bonds compound annually. The difference between daily and monthly compounding on typical rates is small but nonzero.
Is the return realistic?
The S&P 500 has averaged about 10% per year in nominal terms and about 7% after inflation over the long run. Adjust the rate to match your assumptions.