📈 Compound Interest

$20,000 at 6% for 15 Years

Investing $20,000 at 6% annual compound interest for 15 years grows to $47,931. That's $27,931 earned in interest on top of your original $20,000.

If you want to adjust the return assumption, extend the timeframe, or add regular contributions, use the compound interest calculator.

If you want the plain-English explanation behind the numbers, read our guide to compound interest.

Compound Interest Calculator
Australia 2026
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%
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Total value after 15 years
$47,931
Amount invested$20,000
Interest earned$27,931
Interest multiplier2.40×
Year-by-year growth
YearBalanceInterest
Yr 1$21,200+$1,200
Yr 2$22,472+$1,272
Yr 3$23,820+$1,348
Yr 4$25,250+$1,429
Yr 5$26,765+$1,515
Yr 6$28,370+$1,606
Yr 7$30,073+$1,702
Yr 8$31,877+$1,804
Yr 9$33,790+$1,913
Yr 10$35,817+$2,027
Yr 11$37,966+$2,149
Yr 12$40,244+$2,278
Yr 13$42,659+$2,415
Yr 14$45,218+$2,560
Yr 15$47,931+$2,713
Final balance after 15 years
$47,931
Invested
$20,000
Interest earned
$27,931
Multiplier
2.40×

How $20,000 grows at 6%

Compound interest earns returns on your returns — not just your original investment. At 6% per year, your money doubles every 12 years (the Rule of 72). Over 15 years, that compounds to a 2.40× multiplier.

In year 1, $20,000 earns $1,200 in interest. By year 15, the annual interest has grown to $2,713 — because each year's interest is calculated on a larger balance.

This is why longer holding periods matter so much. The later years do more of the heavy lifting, especially once the balance is large enough to generate bigger dollar returns each year.

$20,000 for 15 years at different rates
RateFinal balanceInterest earnedMultiplier
4%$36,019$16,0191.80×
5%$41,579$21,5792.08×
6% ◀$47,931$27,9312.40×
7%$55,181$35,1812.76×
8%$63,443$43,4433.17×
9%$72,850$52,8503.64×
10%$83,545$63,5454.18×

Year-by-year projection

YearBalanceInterest this yearTotal interestGrowth
Year 1$21,200+$1,200$1,2001.06×
Year 2$22,472+$1,272$2,4721.12×
Year 3$23,820+$1,348$3,8201.19×
Year 4$25,250+$1,429$5,2501.26×
Year 5$26,765+$1,515$6,7651.34×
Year 6$28,370+$1,606$8,3701.42×
Year 7$30,073+$1,702$10,0731.50×
Year 8$31,877+$1,804$11,8771.59×
Year 9$33,790+$1,913$13,7901.69×
Year 10$35,817+$2,027$15,8171.79×
Year 11$37,966+$2,149$17,9661.90×
Year 12$40,244+$2,278$20,2442.01×
Year 13$42,659+$2,415$22,6592.13×
Year 14$45,218+$2,560$25,2182.26×
Year 15$47,931+$2,713$27,9312.40×

Growth chart

Balance growth over 15 years
$12k$24k$36k$48kYr1Yr5Yr10Yr15
Principal
Interest earned

Frequently asked questions

Related compound interest scenarios

Use these nearby examples to compare what changes when you keep the same starting balance, extend the investing period, or test a more aggressive return assumption.

Compound interest guide and tools

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