About 401(k) Math
The 401(k) is where most American retirement saving actually happens — payroll-automated, tax-advantaged, and often matched. The match is the headline: a typical “50% up to 6%” formula is an instant 50% return on those dollars, unavailable anywhere else in finance, and roughly a quarter of participants still leave some of it on the table.
Enter your salary, contribution percent, and the match formula from your plan documents (rate and cap), plus current balance, assumed return, and years. You get the projected balance, the yearly free-money figure, the three-way split (yours / match / growth), and the below-cap warning if it applies.
Federal employee? Your version has its own five-part match — the TSP Calculator.
Contribution + Match + Growth
Three streams, one future value:
Yours = salary × your % Match = salary × min(your %, cap %) × match rate FV = (balance)(1+r)ⁿ + monthly total × ((1+r)ⁿ − 1) ÷ r
Worked example: $80,000 salary, 6% contribution, 50%-up-to-6% match, $10,000 balance, 7% for 30 years → about $813,000, built from $154,000 of yours, $72,000 of employer match, and $587,000 of growth. The match alone compounds into six figures of the outcome.
What the Match Is Worth
A 50%-up-to-6% match on an $80,000 salary, compounded at 7% — the cost of under-contributing:
| You contribute | Match captured/yr | Match's 30-yr value | Verdict |
|---|---|---|---|
| 3% | $1,200 (half missed) | ≈ $147,000 | Leaving $1,200/yr unclaimed |
| 6% | $2,400 (full) | ≈ $294,000 | Full match captured |
| 10% | $2,400 (capped) | ≈ $294,000 | Extra 4% grows unmatched |
The middle row is the universal minimum: whatever else your budget decides, contributing to the match cap is the highest-return money move most employees will ever have available.
Limits, Vesting & Fine Print
The IRS caps employee contributions annually (with a higher catch-up allowance from age 50) and adjusts both figures most years — which is why this calculator tells you to check the current limit instead of embedding one that goes stale. High earners hit the cap before high percentages; the math here assumes your percent stays within whatever the current limit allows.
Vesting is the match's asterisk: YOUR contributions are always yours, but employer match may vest over several years — leave early and the unvested portion stays behind, a real number to check before job-hopping. Traditional-vs-Roth 401(k) chooses when taxes hit (now vs at withdrawal) without changing this calculator's growth math; fees inside plan funds subtract directly from the return you assume.