How to plan your retirement savings
Enter your age now and the age you want to retire, your current balance, how much you contribute each month, and an expected annual return. The calculator compounds everything monthly until retirement and shows your projected balance, how much you contributed, and how much came from investment growth.
How the projection is calculated
Each month the calculator does two things: it grows your balance by one month's return, then adds your contribution. In formula terms it combines compound growth on your current savings with the future value of a monthly contribution stream:
Balance = Current × (1+i)n + PMT × [ ((1+i)n − 1) ÷ i ]
where i is the monthly return (annual ÷ 12) and n is the number of months until retirement.
Worked example
You're 30, retiring at 65 (35 years), with $20,000 saved, adding $500/month at a 7% return:
- Total you contribute: $230,000
- Investment growth: ≈ $900,000
- Projected balance at 65: ≈ $1.13 million
Most of that nest egg is growth, not your own deposits — that's compounding at work.
The cost of waiting
Contribute $500/month at 7% from age 25 to 65 and you reach about $1.31 million. Start the very same plan at 35 and you end with roughly $610,000 — less than half. Those ten early years are worth more than all the later ones combined.
Key terms
401(k) — an employer retirement account, often with a match. Employer match — money your employer adds when you contribute. Expected return — the average annual growth you assume. Real return — return after subtracting inflation. Compounding — earning returns on your past returns.
Common mistakes to avoid
Leaving an employer match on the table. Assuming the projected balance is in today's purchasing power — it isn't, unless you use a real (after-inflation) return. Setting an over-optimistic return and under-saving as a result. Pausing contributions in your early years, which costs the most because of lost compounding.
Frequently asked questions
Should I include my employer match?
Yes. Add your employer's monthly match to your own contribution for a complete picture — it's effectively free money.
Does this account for inflation?
No. The figure is in future dollars. Use a lower "real" return (around 4-5%) if you want an inflation-adjusted estimate.
What return rate should I use?
Long-term stock averages have historically been around 6-7% after inflation, but returns aren't guaranteed. Use a rate you're comfortable with.
Why does starting early matter so much?
Compounding rewards time. The example above shows an early start beating much larger late contributions.
What is a 401(k)?
An employer-sponsored retirement account, often with a match and tax advantages. The same math applies to IRAs.
How much should I contribute?
A common guideline is 10-15% of income including any match — but at minimum, contribute enough to get the full employer match.
Can I retire earlier than 65?
Yes — just set a lower retirement age. You'll see how a shorter horizon and fewer contributions change the balance.
Is my data saved?
No. Everything runs in your browser; nothing is uploaded.