Finance Saving

Compound interest calculator

Last reviewed 23 Aug 2026 ·Method: monthly compounding at the stated frequency, contributions in arrears
Starting amount
Added monthly
Rate %
Years
Inflation %
Interest added
Final balance $170,619
You put in $70,000 Growth 59%
You put in$70,000
Interest earned$100,619
In today's money$104,124
Live · contributions and growth shown separately
Year 1Year 20
YearAddedInterest earnedBalance
1 $3,000 $821 $13,821
2 $3,000 $1,097 $17,918
3 $3,000 $1,393 $22,312
4 $3,000 $1,711 $27,023
5 $3,000 $2,052 $32,074
6 $3,000 $2,417 $37,491
7 $3,000 $2,808 $43,300
8 $3,000 $3,228 $49,528
9 $3,000 $3,679 $56,206
10 $3,000 $4,161 $63,368

A projection at a constant rate, which no real investment delivers. It ignores tax, charges and the fact that returns arrive unevenly. Use it to compare choices, not to predict a balance.

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Compound interest is interest earned on interest already earned. A balance growing at rate r for n periods multiplies by (1 + r) raised to n. Ten thousand at 7% with $250 added monthly reaches about $169,000 after twenty years, of which $60,000 is money you put in and the rest is growth.

How to use this calculator

1 Enter what you are starting with and what you plan to add each month.
2 Set the annual rate and how long you are saving for.
3 Choose how often interest is added — the difference between yearly and daily is smaller than people expect.

The bar under the result shows the split between what you contributed and what the money earned. On short horizons contributions dominate and the rate barely matters; somewhere around year fifteen at these numbers the growth overtakes the contributions, and after that the rate is the only thing that moves the answer much. That crossover is the whole argument for starting early.

Questions

Less than the marketing suggests. Ten thousand at 10% for ten years is $25,937 compounded yearly and $27,179 compounded daily — under 5% apart, and the ceiling is continuous compounding at $27,183.

US Securities and Exchange Commission — compound interest
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