Compound Interest Calculator
Calculate compound interest with monthly or annual contributions: final balance, interest earned, growth over time. Adjust rates and periods freely. Free.
Compound interest is the reason "start early" is the most repeated advice in personal finance — and it is hard to feel until you see the curve. Enter a starting amount, interest rate, and contribution schedule, and this calculator projects the final balance with the interest portion separated from principal.
Adjust the rate and timeline freely to stress-test assumptions: the difference between 6% and 8% over 30 years, or starting five years earlier, is usually far larger than intuition suggests.
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Compound Interest Calculator
See how your money grows over time with regular contributions, inflation adjustment, multi-scenario comparison, and growth charts.
| Year | Balance | Contributions | Interest |
|---|---|---|---|
| 1 | $16919 | $16000 | +$919 |
| 2 | $24339 | $22000 | +$2339 |
| 3 | $32294 | $28000 | +$4294 |
| 4 | $40825 | $34000 | +$6825 |
| 5 | $49973 | $40000 | +$9973 |
| 6 | $59782 | $46000 | +$13782 |
| 7 | $70299 | $52000 | +$18299 |
| 8 | $81578 | $58000 | +$23578 |
| 9 | $93671 | $64000 | +$29671 |
| 10 | $106639 | $70000 | +$36639 |
| 11 | $120544 | $76000 | +$44544 |
| 12 | $135455 | $82000 | +$53455 |
| 13 | $151443 | $88000 | +$63443 |
| 14 | $168587 | $94000 | +$74587 |
| 15 | $186971 | $100000 | +$86971 |
| 16 | $206683 | $106000 | +$100683 |
| 17 | $227820 | $112000 | +$115820 |
| 18 | $250486 | $118000 | +$132486 |
| 19 | $274790 | $124000 | +$150790 |
| 20 | $300851 | $130000 | +$170851 |
| 21 | $328796 | $136000 | +$192796 |
| 22 | $358760 | $142000 | +$216760 |
| 23 | $390892 | $148000 | +$242892 |
| 24 | $425345 | $154000 | +$271345 |
| 25 | $462290 | $160000 | +$302290 |
| 26 | $501905 | $166000 | +$335905 |
| 27 | $544384 | $172000 | +$372384 |
| 28 | $589934 | $178000 | +$411934 |
| 29 | $638777 | $184000 | +$454777 |
| 30 | $691150 | $190000 | +$501150 |
P = principal · PMT = monthly contribution · r = annual rate · n = compounding periods per year · t = years. This calculator uses the exact period-compounded form and honors in-period contribution timing (start vs end).
With monthly compounding at 7% on a starting 10,000 and 500/month contributed at the end of each period for 30 years:
- Final balance:$691,150
- You contributed:$190,000
- Interest earned:+$501,150
The 2.5% inflation adjustment is based on the trailing 12-month CPI-U average. Actual inflation varies. Investment returns are not guaranteed. Past performance does not predict future results. This is for estimation only — consult a financial advisor.
The shaded band between the two curves is interest earned on interest. Compounding is slow at first, then accelerates — the longer the horizon, the wider the gap.
About this compound interest calculator
This page covers compound interest formula calculator, investment growth calculator, savings compound calculator, interest compounding monthly calculator — all the same underlying task as compound interest calculator. The tool above is FreeToolHub's compound embedded in full: every feature works right here, and nothing you process is uploaded to any server.
Frequently asked questions
What is the compound interest formula?
A = P(1 + r/n)^(nt) for a principal P at annual rate r compounded n times per year over t years. Regular contributions add an annuity term. This calculator handles the full schedule — monthly deposits, compounding frequency, and time — so you do not have to fight the algebra.
Is compound interest the same as APY?
APY (annual percentage yield) is what compounding does to a nominal rate over one year — 6% compounded monthly is 6.17% APY. When comparing savings accounts and investments, compare APYs; when projecting growth over years, use the calculator with your actual contribution schedule.