See how your money grows over time. This free compound interest calculator lets you add a starting deposit and regular monthly contributions, choose how often interest compounds, and instantly see your future value and total interest earned.
Results update automatically as you type. Estimates only — actual returns vary and are not guaranteed.
How Compound Interest Calculator Works
Compound interest grows a balance because each round of interest is calculated on the principal plus every prior round of interest already earned, not just the original deposit. The compound interest calculator projects this growth for both a lump-sum starting deposit and any regular monthly contributions you add on top, across the compounding frequency you choose.
Formula: FV = P × (1 + i)^N + PMT × [(1 + i)^N − 1] / i, where i = r ÷ n and N = n × t
- FV — the future value shown as the result
- P — the initial deposit
- PMT — the contribution added each compounding period (built from your monthly contribution)
- r — the annual interest rate you enter
- n — the compounding frequency per year (365 for daily, 12 for monthly, 4 for quarterly, 1 for yearly)
- t — the number of years
Example Scenarios
| Initial Deposit | Monthly Contribution | Rate | Years | Future Value (monthly compounding) |
|---|---|---|---|---|
| $0 | $200 | 8% | 15 | $69,208 |
| $2,000 | $50 | 4% | 10 | $10,344 |
| $5,000 | $100 | 6% | 20 | $62,754 |
| $10,000 | $0 | 7% | 10 | $20,097 |
| $50,000 | $0 | 5% | 25 | $174,063 |
Compound Interest Calculator FAQ
How much does compounding frequency actually change the future value?
Switching from yearly to daily compounding increases the future value slightly because interest starts earning its own interest sooner, but the effect is modest at typical savings rates. The size and time horizon of your deposits and contributions matter far more than the compounding frequency.What’s the difference between the initial deposit and monthly contributions in the result?
The initial deposit grows on its own from day one, compounding for the full time period, while each monthly contribution only compounds for the months remaining after it’s added. That’s why the “total invested” and “interest earned” totals are shown separately from the future value.Why does a longer time horizon matter more than a higher interest rate?
Because each compounding period builds on all previous growth, the curve accelerates the longer money stays invested — an extra 10 years often adds more to the future value than a couple of extra percentage points of rate. Time is doing exponential, not linear, work.Does the calculator account for inflation or taxes on the interest earned?
No — the future value shown is a nominal, pre-tax projection based purely on the rate, deposit, contributions, and compounding frequency you enter. Actual purchasing power and after-tax returns will be lower once inflation and taxes are factored in.How is the monthly contribution converted when I choose quarterly or yearly compounding?
The calculator keeps your annual contribution total consistent by converting the monthly amount into an equivalent contribution per compounding period, so switching frequency doesn’t silently change how much you’re contributing per year.Is the interest rate I enter the same as an account’s APY?
Not exactly — the rate you enter is the nominal annual rate before compounding, while APY already reflects the effect of compounding. If your account only advertises APY, the future value estimate may differ slightly depending on the frequency you select.Related Calculators
Once you’ve seen how a lump sum and monthly contributions grow here, you can model a broader investment portfolio’s growth or project how these savings fit into your retirement timeline. For a fixed monthly SIP-style contribution schedule, the SIP calculator offers a more India-market-specific view of the same math.