What is 401(k) Calculator?
When to Use This Calculator
- When you first enroll - set a deferral at least equal to the match threshold before optimizing anything else.
- Each January, when the IRS publishes new limits - re-check that your payroll percentage still fills the room.
- After a raise - convert part of the increase into deferral before lifestyle spending absorbs it.
- From age 49 to 50 and again at 60 - catch-up eligibility changes the math and the maximum percentage.
- When comparing job offers - run both plans' match rules in Employer match mode to price the real difference.
- If your statement surprises you - the schedule shows where every dollar came from: you, the employer, or growth.
Steps:
- Pick the mode that matches your question: Project balance to plan the horizon, Max out to solve the 2026 limit, or Employer match to price unclaimed match.
- Enter salary and age - the IRS caps key off both: $24,500 of base deferral, plus $8,000 from age 50 and $11,250 between ages 60 and 63.
- Set the deferral rate and starting balance; Max out mode replaces your rate with the exact percentage that fills your personal limit.
- Describe the plan's match: the rate it pays and the percentage of salary it matches up to - 50% up to 6% is the classic design.
- Adjust the return, inflation and horizon under Growth assumptions; the defaults are 7%, 2.5% and the preset's horizon.
- Read the hero line for the headline figure, then the four stat cards: your contributions, employer money, investment growth and the share of the limit used.
- Work through the year-by-year schedule or flip to its chart, and scan the sensitivity grid across 10 to 40-year horizons and 4% to 10% returns.
- Switch to Employer match mode to study the deferral ladder and see what each rate earns before deciding where to set your percentage.
Formula
Use Cases
- Planning the next 20 years: enter salary, deferral and balance once, then read the ending figure in today's money.
- Sizing a raise split: convert each 1% of salary increase into extra deferral measured against the $24,500 ceiling.
- Deciding when to overflow: Max out shows the exact percentage that fills the 2026 limit before extra saving spills into an IRA.
- Auditing your plan document: type the stated match rate and threshold to confirm payroll is paying every dollar you are owed.
- Catch-up planning at 50 and 60: the same paycheck suddenly has $8,000 - or $11,250 at ages 60 to 63 - of extra room to exploit.
- Comparing job offers: a 50% match up to 6% is worth thousands a year - price it in Employer match mode against a weaker plan.
Key Benefits
- Three questions, one engine: project the horizon, solve the maximum, or price the match without re-entering your data.
- Catch-up aware by age: 50 to 59 gets $8,000, 60 to 63 gets $11,250, and Max out mode converts the room into an exact percentage.
- Honest inflation math: every projection reports the nominal ending balance beside what it actually buys in today's money.
- Match leakage is quantified: unclaimed employer dollars appear as a horizon total, a yearly figure and a ladder comparison.
- Limits stay current: the 2026 figures come straight from IRS Notice 2025-67, including the $24,500 base and the $72,000 additions cap.
- One model covers 401(k), 403(b) and 457(b) - the contribution rules are identical for 2026, so switching account type only relabels the output.
Pro Tips
- Raise the deferral by 1% each year until Max out mode reports the limit is full - the change is small and automates with payroll.
- Capture the full match before anything else, including high-interest debt - no other account returns an instant 50% on contribution day.
- Front-load bonuses and raises: dollars invested earlier compound longer than the same dollars in your final working years.
- Check the sensitivity grid: small changes in return or horizon move the ending balance more than most contribution tweaks do.
- Re-run Max out after every birthday - the catch-up thresholds at 50 and 60 are automatic raises in contribution room.
- Pair the plan with an IRA once the 401(k) limit is full; Max out mode tells you exactly when that moment arrives.
Common Mistakes to Avoid
- Deferring enough to earn some match but not all: anything below the threshold percentage donates employer money every single year.
- Forgetting catch-up room: savers over 50 often leave the extra $8,000 - or $11,250 at ages 60 to 63 - unused because payroll was never updated.
- Confusing the deferral limit with the total limit: $24,500 is yours alone, while employers can add up to $72,000 of annual additions.
- Judging the balance in nominal dollars: $1,101,544 in twenty years funds far less than it sounds like once 2.5% inflation is applied.
- Leaving the match on the table while chasing fund performance: an instant 50% return up to 6% of salary beats almost any investment decision.
- Assuming the Roth catch-up rule applies to everyone: only prior-year wages at or above $150,000 trigger mandatory Roth treatment.
Key Terms Explained
- Elective deferral:
- the salary you postpone into the plan - $24,500 for 2026 before any catch-up is added.
- Catch-up contribution:
- the extra amount savers 50 and over may defer - $8,000 in 2026, or $11,250 at ages 60 to 63.
- Annual additions:
- everything that lands in the plan from you and your employer, capped at $72,000 for 2026 before catch-up.
- Employer match:
- plan money keyed to your deferral, usually 50% of what you contribute up to a set percentage of pay.
- Match threshold:
- the salary percentage where the match stops paying - defer at least this much or leave money behind.
- Limit used:
- your annual contribution as a share of the 2026 capacity for your age and salary.
- Real balance:
- the ending balance restated in today's money after dividing out cumulative inflation.
- Roth catch-up:
- mandatory Roth treatment of catch-up dollars when prior-year wages reach $150,000 under SECURE 2.0.
Related Concepts
- Roth IRA Calculator: the natural overflow account once the 401(k) limit is filled - the same tax-free growth with no employer match attached.
- Retirement Calculator: widens the view from one account to every source of retirement income and spending.
- Compound Interest Calculator: isolates the growth engine this projection uses - monthly compounding at your annual rate.
- Investment Calculator: models taxable investing for the dollars that cannot fit inside the plan's limits.
- Social Security Calculator: estimates the baseline income layer beneath whatever this plan accumulates.
- HSA Contribution Calculator: another tax-advantaged bucket to fill once the 401(k) is maxed, with triple tax benefits.

