Comprehensive Guide
Learn more in our Investing Guide.
How it works
The most important 401(k) rule is: always contribute at least enough to get the full employer match. If your employer matches 50% of contributions up to 6% of salary, and you earn $80,000, contributing 6% ($4,800) gets you $2,400 in free money from your employer. That is an instant 50% return on your money — better than any investment. This calculator shows your optimal contribution percentage, annual contribution amount, employer match value, and annual tax savings. Beyond the match, aim to contribute 15% of your income total (including employer match). At $80,000 salary, that is $12,000/year in contributions. The tax savings at 24% bracket: $2,880/year. Every field in this calculator exists for a reason. Enter Annual Salary, Employer Match %, Match Cap %, Current Contribution %, Annual Contribution, and the engine recomputes the results instantly — no signup, no email, and nothing is sent to a server, because the math runs entirely in your browser. Change one input at a time to see which lever moves the result most; that sensitivity, not any single number, is usually the real insight. The worked example below the form uses realistic defaults so you can sanity-check the output before trusting it with your own figures, and the formula is published on the page so you can verify every step of the arithmetic yourself.Tips
- Start with the default values to see a baseline result, then change one input at a time to understand which factor matters most for your outcome.
- Replace every default with your actual number — estimates and rules of thumb produce estimates, not answers. Pull your real figures from pay stubs, statements, or account dashboards.
- Use a conservative return rate (5-6% rather than the historical 10%) for planning purposes. Markets have long flat stretches, and planning on the average sets you up for a shortfall.
Frequently asked questions
How much should I put in my 401k?
At minimum: 6% to capture full match ($4,800). Employer adds $2,400. Ideal: 15% total ($12,000). Tax savings: $2,880.
What does the 401(k) contribution optimizer calculate?
It takes annual salary, employer match %, match cap %, current contribution % as inputs and computes annual contribution, employer match $, annual tax savings. The primary output is annual contribution. Optimize your 401(k) contributions to maximize employer match and tax benefits.
How accurate are the calculator results?
The math is exact — the same formulas a financial professional would use by hand. The precision of the output depends entirely on how realistic your inputs are. Use your actual numbers rather than estimates when possible. The defaults are reasonable starting points, but your real income, rates, and timeline will produce a different result.