💰 Investment Calculator

Project investment growth with a starting amount and monthly contributions.

About this tool

Projects the future value of an investment that starts with a lump sum and adds a fixed monthly contribution, compounding monthly at your expected annual return rate.

Separates the result into how much you actually contributed versus how much came purely from investment growth, so you can see compounding at work. If your goal is specifically retirement, the Retirement Savings Calculator uses this same math but anchors it to your current and target retirement age, and adds an estimated retirement income on top.

Worked example

Starting with $5,000, adding $200/month, at a 7% annual return for 20 years, projects to roughly $110,000 — with about $53,000 of that from contributions and the rest from growth.

How to use it

Enter your starting amount.
Enter your planned monthly contribution.
Enter an expected annual return rate.
Enter the number of years, then press Project growth.

Tips

Expected return is never guaranteed — this is a projection based on a constant rate, not a promise. Real markets are volatile year to year.
Small increases in monthly contribution compound significantly over decades — try adjusting the number to see the effect.
For a lump sum with no ongoing contributions, set the monthly contribution to 0 and this behaves like a standard compound interest calculator.

FAQ

What return rate should I use?

That's a personal assumption based on your investment mix — long-run stock market averages are often cited around 7–10% before inflation, but this tool doesn't predict future returns, it just projects a chosen rate forward.

Does this account for inflation?

No — the projected value is in future (nominal) dollars. Use the Inflation Calculator alongside this one to see what that amount is worth in today's purchasing power.

Does it account for taxes on investment gains?

No — this is a pre-tax projection. Actual after-tax growth depends on your account type and local tax rules.

From the blog: getting the most out of this tool

The number people usually fixate on is the final total, but the more useful number here is often the contribution-vs-growth split — seeing that a large chunk of a 20-year total came from compounding, not from money you personally put in, is what makes starting early click.

We built this to sit next to our Compound Interest and Retirement Savings calculators rather than replace them — this one is tuned specifically for the "lump sum plus steady monthly contribution" scenario most people actually have.

📖 Want the fuller explanation?

See Compound vs Simple Interest for the reasoning behind this calculation, with worked examples.