Retirement calculator
Retirement savings grow from three inputs: what you already have, what you add each month, and how long that money stays invested. This calculator projects your balance forward at a steady annual growth rate and draws a year-by-year chart so you can see how much of the final number comes from your own contributions versus growth.
How the math works
Every month, the calculator applies your growth rate to the current balance, then adds your monthly contribution - the same compounding process a real account goes through, just sped up. The result includes an SVG chart plotting your projected balance against your total contributions year by year; the growing gap between the two lines is compounding, not new money you put in. A small change in the growth-rate assumption swings the final number a lot over 20–30 years, which is why the result is framed as a projection based on a steady rate, not a guarantee of what markets will actually return.
Related reading
For a sense of what target numbers commonly get used, see how much you need for retirement and choosing a target retirement age. If a single savings number feels too rigid, is it realistic to use a single number as a retirement savings goal covers the limits of that approach, and what compound interest is and why it matters for investing explains the growth mechanism this calculator is built on.
The formula this calculator uses
r = annual rate / 100 / 12
each month: balance = balance * (1 + r) + monthly contribution
over years * 12 months
What it assumes without asking
- The contribution never rises, though most people’s pay does
- One steady return, applied monthly
- No fees, no taxes, no withdrawals and no career break
One example, computed in full: $25,000 now plus $500 a month at 6%
| After | You contributed | Growth | Balance |
|---|---|---|---|
| 5 years | $55,000 | $13,606 | $68,606 |
| 10 years | $85,000 | $42,425 | $127,425 |
| 15 years | $115,000 | $91,762 | $206,762 |
| 20 years | $145,000 | $168,776 | $313,776 |
| 25 years | $175,000 | $283,121 | $458,121 |
| 30 years | $205,000 | $447,822 | $652,822 |
What this calculator does not model
- What the balance is worth after inflation
- How long the money has to last, which is the other half of the question
- Taxes on withdrawal, which depend on the account type
- Any employer contribution, which the 401(k) tool covers separately
The guide behind this tool
A number on its own does not tell you what to do with it. Starting to invest with little money covers what each monthly amount becomes, and Roth against traditional covers how the balance above is taxed on the way out.
Sources & further reading
This tool is a general educational estimate, not financial advice or an investment projection guarantee. Actual returns vary and can be negative in any given year. See our disclaimer.