Free calculator

Compound Interest Calculator

Monthly compounding with your own numbers. Everything recalculates as you type.

Advanced options
Final balance after 20 years$56,131
Contributed $25,000Interest $31,131
Total contributed
$25,000
Interest earned
$31,131
Growth multiple
2.25×
$0$28k$56k048121620BalanceContributed
Year-by-year breakdown
YearBalanceContributedInterest earned
1$2,312$2,200$112
2$3,718$3,400$318
3$5,226$4,600$626
4$6,843$5,800$1,043
5$8,577$7,000$1,577
6$10,436$8,200$2,236
7$12,430$9,400$3,030
8$14,568$10,600$3,968
9$16,860$11,800$5,060
10$19,318$13,000$6,318
11$21,954$14,200$7,754
12$24,780$15,400$9,380
13$27,811$16,600$11,211
14$31,061$17,800$13,261
15$34,545$19,000$15,545
16$38,282$20,200$18,082
17$42,288$21,400$20,888
18$46,585$22,600$23,985
19$51,192$23,800$27,392
20$56,131$25,000$31,131

Saved results

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How this is calculated

Balance compounds monthly: each month the balance is multiplied by(1 + annual_rate / 100 / 12), then the monthly contribution is added. This repeats for years × 12 months. Interest earned is the final balance minus your initial amount plus all contributions. In advanced mode, the inflation-adjusted value divides each year's balance by (1 + inflation) ^ year to show purchasing power in today's dollars.

FAQ

What is compound interest?

Compound interest is interest calculated on both your original balance and the interest that balance has already earned. Because each period's interest gets added back into the balance, growth accelerates over time compared to simple interest.

How often does this calculator compound?

Monthly. Each month, the current balance is multiplied by (1 + annual rate / 12), then your monthly contribution is added. This matches how most savings and investment accounts compound in practice.

What annual return should I use?

That depends on the asset you're modeling. A high-yield savings account, a bond portfolio, and a stock index fund have very different long-run averages. This tool does not recommend a rate; use a figure appropriate to your own situation, or run several scenarios to see a range of outcomes.

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Informational tool only. Not financial advice. See our disclaimer.