Finance

Compound Interest Calculator

Model investment growth with contributions, compounding, inflation drag, and taxes. Curve + scenarios + cited benchmarks.

NOMINAL
compound.ledger/7.00pct.20y.12cpy
◉ as of May 13, 2026
Future value · year 20
$300.9K× 30.1 principal
+ $170,851 earned7.00% · monthly57% interest share
Total contributed
$130,000
Interest earned
$170,851
Effective rate
7.00%
Multiple on principal
30.09×
// Real rate ≈ 3.88% via Fisher: (1+nom)/(1+inf) − 1.
Compounding

Terms

Inputs · USD

Growth curve · contributions vs interest

Year-end balances. Lower band is what you put in. The gap is what compounding made.

ContributionsInterest
$300.9K$198.6K$99.3K$0
Yr 0Yr 10Yr 20
YearCompositionBalance% int.
Yr 01
$16,9195%
Yr 02
$24,33910%
Yr 03
$32,29413%
Yr 04
$40,82517%
Yr 05
$49,97320%
Yr 06
$59,78223%
Yr 07
$70,29926%
Yr 08
$81,57829%
Yr 09
$93,67132%
Yr 10
$106,63934%
Yr 11
$120,54437%
Yr 12
$135,45539%
Yr 13
$151,44342%
Yr 14
$168,58744%
Yr 15
$186,97147%
Yr 16
$206,68349%
Yr 17
$227,82051%
Yr 18
$250,48653%
Yr 19
$274,79055%
Yr 20
$300,85157%

Scenarios · 4% / base / 10%

Same principal, monthly, and horizon — different rate regime.

Conservative4.0%
$205.6K
Earned $75,613
Base7.0%
$300.9K
Earned $170,851
Aggressive10.0%
$453.0K
Earned $322,965

Benchmark returns

Long-run context
  • S&P 500 real 1928-20246.9%Stern / Damodaran
  • S&P 500 nominal 1928-20249.8%Stern / Damodaran
  • 10-yr US Treasury 1928-20244.6%Stern / Damodaran
  • 60/40 portfolio (real)5.4%Vanguard research 2024
  • Gold real 1928-20240.9%Stern / Damodaran
  • US inflation avg 1928-20243.1%BLS CPI-U

Past performance is not a forecast. 95-year windows smooth out regimes you'll actually live through.

Compounds at the chosen frequency. Monthly contributions are split across periods. Inflation toggle uses Fisher; tax toggle drags earnings each period. Ignores sequence-of-returns risk, fees, and behavioral drift.