How to use the Investment Calculator
- Enter your Initial investment.
- Enter your Monthly contribution.
- Enter your Expected annual return.
- Enter your Time horizon.
- Pick a Compounding frequency.
- Read the result — it updates instantly as you type.
Worked example
Invest $10,000 up front, add $500 a month, earn 8% a year compounded monthly for 20 years.
- Initial investment: $10,000; Monthly contribution: $500
- Expected annual return: 8%; Time horizon: 20 years
Result: $343,778 You invested $130,000 in total, so about $213,778 — over half the final balance — comes from compounding.
What is an investment calculator?
An investment calculator shows the future value of money you invest today plus money you add over time, assuming a steady annual return. The math is the same compound-growth model used for savings and retirement planning.
The investment growth formula
FV = P(1 + r/n)nt + PMT × [((1 + r/n)nt − 1) / (r/n)]
Where P is your initial investment, PMT the monthly contribution, r the annual return (decimal), n compounding periods per year, and t years.
Frequently asked questions
Is an 8% return realistic?
Historically the S&P 500 has returned about 7–10% annually before inflation over long periods, but year-to-year results vary widely. Use a conservative number for planning.
Does this include fees or taxes?
No. Brokerage fees, expense ratios, and capital-gains taxes all reduce real returns. Treat the output as a pre-tax, pre-fee estimate.
How accurate is this calculator?
Mathematically exact for the inputs you provide. It cannot predict market returns — only model a fixed rate you choose.