Compound Interest Calculator
See how your savings and investments grow over time with compound interest and regular contributions. Adjust for inflation to see real purchasing power.
Your Investment
$10,000
$500/mo
7%
S&P 500 historical average: ~10% (7% after inflation)
30 years
3%
Your Investment Will Grow To
$694,709
In today's dollars: $286,211 (adjusted for 3% inflation)
Total Deposited
$190,000
27% of final
Interest Earned
$504,709
73% of final
Growth Over Time
Year 1
$16,955
Year 5
$50,182
Year 10
$107,144
Year 15
$187,895
Year 20
$302,370
Year 25
$464,653
Year 30
$694,709
Contributions
Interest
How This Calculator Works
Compound interest formula (without contributions):
A = P × (1 + r/n)^(n×t)
Where P = principal, r = annual interest rate, n = compounding periods per year, t = years.
With regular contributions, each contribution is treated as its own compound interest series and summed. For monthly contributions C:
A = P×(1+r/n)^(nt) + C×[(1+r/n)^(nt) − 1] / (r/n)
Inflation adjustment: the real value is calculated by deflating the nominal balance by the inflation rate each year: Real Value = Nominal Balance / (1 + inflation)^t.