401(k) Calculator
Project your 401(k) with contributions and employer match.
All calculations happen locally in your browser — nothing is uploaded, stored or tracked.
Enter your salary and age
Current figures.
Set contribution and match
Your % of salary and the employer match.
Set growth and tax assumptions
Expected return, salary growth and retirement tax rate.
What Is a 401(k)?
A 401(k) is a tax-advantaged retirement account offered by US employers. Contributions are pre-tax (traditional) or post-tax (Roth), often matched by the employer up to a percentage of salary, and investments grow tax-deferred until withdrawal.
The calculator projects the balance at retirement from your salary, contribution rate and employer match, and shows both the pre-tax and post-tax value of the account at withdrawal.
The Model
Salary grows at the salary-growth rate you assume; the account earns the expected return. At retirement, the tax rate you enter is applied to the traditional (pre-tax) balance. All rates are your assumptions — nothing is fetched live.
Your data never leaves your device.
Every calculation on this site runs in your browser using vanilla JavaScript. Nothing is uploaded, stored or tracked.
- 100% local, client-side calculations
- No data stored on any server
- No tracking, no analytics, no ads scripts
- Works offline once loaded
Frequently Asked Questions
How much should I contribute to my 401(k)?
At least up to the employer match — that is free money. A common target is 10–15% of income including the match.
What is an employer match?
The employer contributes a percentage of your salary (often 3–6%) when you contribute — typically up to a cap.
Traditional vs Roth — which is better?
Traditional defers tax (good if your retirement rate is lower); Roth taxes now (good if it will be higher). The calculator shows the tax impact either way.
What return should I assume?
A diversified portfolio historically averages roughly 7% nominal over long periods. Use a conservative assumption.
Is this financial advice?
No — it is a projection tool using the assumptions you enter.