Compound Interest Calculator
The most transparent calculator online — see exactly how your money grows.
📊 Calculator Inputs
$
$
7%
%
20 yrs
years
$
📈 Results
Final Balance
$300,851
After 20 years
Total Interest Earned
$170,851
Total Contributions
$130,000
Interest / Contribution Ratio
1.31×
Interest earned per $1 contributed
⏱️ Time to Double
~10 yrs, 3 mo
Based on the Rule of 72 — a quick estimate of how long it takes for your investment to double.
📊 Effective Annual Rate (APY)
7.23%
Your nominal 7% compounded monthly yields an effective rate of 7.23%
🔍 Calculation Assumptions(what other calculators hide)
- Contributions made at: end of each month
- Interest compounded: monthly (12×/yr)
- Inflation adjustment: Off — fixed contribution amount
- Formula: A = P(1 + 0.005833)^(nt) + PMT × [((1 + 0.005833)^(nt) – 1) / 0.005833] [end-of-period]