Compound Interest Calculator — With Monthly Contributions
See how your savings grow year by year. Set a starting amount, monthly contribution, rate, and time — get the final balance, interest earned, and a full breakdown table.
Final balance
$109,333
Total contributed
$58,000
Interest earned
$51,333
| Year | Balance | Contributed | Interest |
|---|---|---|---|
| 1 | $12,967 | $12,400 | $567 |
| 2 | $16,087 | $14,800 | $1,287 |
| 3 | $19,365 | $17,200 | $2,165 |
| 4 | $22,812 | $19,600 | $3,212 |
| 5 | $26,435 | $22,000 | $4,435 |
| 6 | $30,243 | $24,400 | $5,843 |
| 7 | $34,246 | $26,800 | $7,446 |
| 8 | $38,454 | $29,200 | $9,254 |
| 9 | $42,877 | $31,600 | $11,277 |
| 10 | $47,527 | $34,000 | $13,527 |
| 11 | $52,414 | $36,400 | $16,014 |
| 12 | $57,551 | $38,800 | $18,751 |
| 13 | $62,951 | $41,200 | $21,751 |
| 14 | $68,628 | $43,600 | $25,028 |
| 15 | $74,595 | $46,000 | $28,595 |
| 16 | $80,867 | $48,400 | $32,467 |
| 17 | $87,460 | $50,800 | $36,660 |
| 18 | $94,390 | $53,200 | $41,190 |
| 19 | $101,675 | $55,600 | $46,075 |
| 20 | $109,333 | $58,000 | $51,333 |
For education only — not financial advice. Actual returns vary.
New to compounding? Read the plain-English explainer with tables: How compound interest actually grows your money
Frequently Asked Questions
How does compound interest work?▼
You earn interest not only on your original money but also on the interest already earned. Each period the balance grows, and the next period’s interest is calculated on that larger balance — which is why growth accelerates over time.
How much difference do monthly contributions make?▼
A huge one. $10,000 at 5% for 20 years grows to about $27,000 alone — but adding $200 a month brings it to roughly $109,000, of which over $40,000 is interest. Use the calculator to try your own numbers.
What does compounding frequency mean?▼
How often interest is added to your balance: yearly, quarterly, monthly, or daily. More frequent compounding earns slightly more, but the difference between monthly and daily is usually tiny — the rate and time matter far more.
What is the Rule of 72?▼
A quick mental shortcut: divide 72 by the annual interest rate to estimate how many years it takes money to double. At 6%, that is about 12 years; at 9%, about 8 years.
Is this calculator financial advice?▼
No — it is an educational tool that assumes a steady rate of return. Real investments fluctuate and may lose value. Consult a licensed adviser for personal financial decisions.