CompoundFX

Compound Interest Calculator

Compound interest is interest calculated on your initial deposit plus all previously earned interest. Because each period's interest is added to the balance before the next calculation, your money grows exponentially rather than linearly.

Calculate compound interest

Your Inputs

Monthly contributions compound monthly, so the frequency is locked to monthly while you're contributing.

Results

Year-by-Year Growth Table

Year-by-year growth of $10,000 at 7% with $200 monthly contributions over 30 years
YearStart BalanceContributionsInterestEnd Balance
1$10,000.00$2,400.00$801.42$13,201.42
2$13,201.42$2,400.00$1,032.85$16,634.27
3$16,634.27$2,400.00$1,281.01$20,315.28
4$20,315.28$2,400.00$1,547.11$24,262.39
5$24,262.39$2,400.00$1,832.45$28,494.83
6$28,494.83$2,400.00$2,138.41$33,033.24
7$33,033.24$2,400.00$2,466.49$37,899.74
8$37,899.74$2,400.00$2,818.29$43,118.03
9$43,118.03$2,400.00$3,195.52$48,713.55
10$48,713.55$2,400.00$3,600.02$54,713.58
11$54,713.58$2,400.00$4,033.77$61,147.34
12$61,147.34$2,400.00$4,498.86$68,046.20
13$68,046.20$2,400.00$4,997.58$75,443.79
14$75,443.79$2,400.00$5,532.35$83,376.14
15$83,376.14$2,400.00$6,105.79$91,881.93
16$91,881.93$2,400.00$6,720.67$101,002.60
17$101,002.60$2,400.00$7,380.00$110,782.60
18$110,782.60$2,400.00$8,087.00$121,269.60
19$121,269.60$2,400.00$8,845.11$132,514.70
20$132,514.70$2,400.00$9,658.02$144,572.72
21$144,572.72$2,400.00$10,529.69$157,502.41
22$157,502.41$2,400.00$11,464.38$171,366.79
23$171,366.79$2,400.00$12,466.64$186,233.43
24$186,233.43$2,400.00$13,541.35$202,174.77
25$202,174.77$2,400.00$14,693.75$219,268.52
26$219,268.52$2,400.00$15,929.46$237,597.98
27$237,597.98$2,400.00$17,254.49$257,252.47
28$257,252.47$2,400.00$18,675.32$278,327.79
29$278,327.79$2,400.00$20,198.86$300,926.65
30$300,926.65$2,400.00$21,832.53$325,159.17

Final Balance

$325,159.17

Total Contributions
$82,000.00
Total Interest
$243,159.17
Final Balance
$325,159.17
$0$81K$163K$244K$325K08152330

The Power of CompoundingYou contributed $82,000 but earned $243,159 in interest.

Why Compound Interest Changes Everything

Unlike simple interest, compound interest earns interest on both your initial investment and the interest that accumulates over time, so every year of head start multiplies the end result.

  • Start small and grow big
  • Time is your greatest asset
  • Consistency beats timing
Learn how it works →

The Earlier You Start, The More You Grow

Investing $200/month at 7% until age 65: starting at 25 grows to $524,963 ; starting at 35 grows to $243,994 ; starting at 45 grows to $104,185 .

$0K $131K $262K $394K $525K 25 35 45 55 65
  • Started at 25: $524,963
  • Started at 35: $243,994
  • Started at 45: $104,185

The Compound Interest Formula

The math behind the growth: every variable explained.

See the formula →
A=P(1+rn)ntA = P\left(1 + \frac{r}{n}\right)^{nt}
A
= final amount (future value)
P
= principal (initial deposit)
r
= annual interest rate (decimal)
n
= times compounded per year
t
= time in years

Take this projection further in CompoundFX

CompoundFX brings this calculation to your iPhone and adds inflation, tax, and expense-ratio adjustments, a real-time growth chart with milestone markers, and a year-by-year breakdown, all free.

See every CompoundFX feature →
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CompoundFX for iPhone

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