Starlight Tools

401(k) Calculator

Project employee deferrals, employer match, IRS limit caps, inflation-adjusted value, and retirement withdrawals. Everything runs locally in your browser.

Inputs

Results

Balance at retirement$0
Today's money$0
Total employee contributions$0
Total employer match$0
Total investment growth$0
First-year contribution$0

Enter assumptions to see the projection.

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How this 401(k) calculator works

The projection compounds monthly. During working years, it grows the balance by the expected annual return divided into monthly periods, then adds monthly employee and employer contributions. Salary is increased once per year by the salary-growth assumption.

  • Employee contribution: annual salary x contribution percentage, capped by the selected IRS deferral limit when the limit option is enabled.
  • Employer match: salary x the smaller of your contribution percentage and the match cap x employer match percentage.
  • Real balance: retirement balance divided by cumulative inflation through retirement age.
  • Withdrawals: after retirement, the tool subtracts your monthly withdrawal and keeps applying the expected monthly return.

The default IRS limits are based on the IRS 2026 401(k) contribution limit notice: employee elective deferrals of $24,500, catch-up of $8,000 for age 50+, and a higher $11,250 catch-up for ages 60-63. Source: IRS 401(k) and profit-sharing plan contribution limits.

This is an educational estimate, not financial, tax, or legal advice. It does not model taxes, Roth income rules, required minimum distributions, investment fees, vesting schedules, loans, hardship withdrawals, plan testing limits, or market volatility.

FAQ

Should I enter pre-tax or Roth 401(k) contributions?

Use the same contribution percentage either way. This tool projects account growth before taxes. A Roth 401(k) and traditional 401(k) can have different tax outcomes, but the contribution and compounding mechanics are the same for this estimate.

How is employer match calculated?

If your employer matches 50% up to 6% of salary, enter 50 for employer match and 6 for match cap. With an $85,000 salary and a 10% employee contribution, the estimated first-year match is $2,550.

Why can my contribution be lower than my selected percentage?

When the IRS limit option is on, employee deferrals are capped by the selected year's regular and catch-up limits. Your plan may also impose lower limits.

Does this include Social Security or pensions?

No. It isolates 401(k) savings. Use the retirement planner for a broader view of savings and spending assumptions.

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