Investment Calculator
Calculate how investments grow over time with regular monthly contributions. See the compounding effect on any starting amount at any return rate.
Part of our Finance Calculators collection.
Investment Calculator
Free online calculator
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S&P 500 historical average ~10% nominal, ~7% real
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How to Use This Calculator
- 1
Enter your starting amount and monthly contribution.
- 2
Set the expected annual return.
- 3
Enter the investment period.
- 4
See projected final value and total gains.
Investment Growth Formula
FV = P(1+r)^n + PMT × [(1+r)^n − 1]/r P = initial, r = monthly rate, n = months, PMT = monthly contribution
Example Calculation
Example: $5,000 start, $500/month, 8% return, 20 years
Inputs
initialAmount: 5000monthlyContribution: 500annualReturn: 8years: 20
Result
$307,540
$5,000 + $500/mo for 20 years at 8% = $307,540. You contributed $125,000 — investing added $182,540.
Frequently Asked Questions
What return rate should I use?
The S&P 500 has returned ~10% annually before inflation over the long term. Use 6–8% for a conservative diversified portfolio estimate.
Should I use a 401k or IRA?
Maximize employer 401k match first (free money), then Roth IRA if eligible, then additional 401k. Tax-advantaged accounts compound faster.