401k Calculator
Project a 401(k) to retirement and price the one component nobody negotiates for: the employer match you are either capturing in full or quietly leaving behind.
401k Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Results are a model, not a quotation — an institution's own figures govern.
- Every input is an assumption; change one and the answer changes with it.
- Rounding is applied only at the display layer, so totals may differ by a cent from a statement that rounds each line.
In short: On an $85,000 salary contributing 6% with a 50% match capped at 6%, a $40,000 balance grows to $745,437.43 over 25 years at 7%. The employer's $63,750 of matching becomes $172,140.23 — a 2.70x multiple — and contributing only 3% instead would forfeit $258,210.35.
Formula
B = current balance · C = combined annual contribution · i = monthly return · n = months. The match is capped at the lesser of your rate and the plan's limit.
Worked Example
- Compute your contribution. $85,000 × 6% = $5,100 a year.
- Compute the match. The cap binds at 6%, so $85,000 × 6% × 50% = $2,550 a year.
- Grow the existing balance. $40,000 at 7% for 300 months.
- Add the contribution stream. $637.50 a month combined, compounding monthly, giving $745,437.43 in total.
- Isolate the match. Without it the projection is $573,297.20, so the match is worth $172,140.23.
Analyst's note. The employer contributes $63,750 across the period and it arrives as $172,140.23 — a 2.70× multiple, earned purely by time in the market. Note the asymmetry in the other direction too: dropping to a 3% contribution costs $258,210.35, far more than the $63,750 of forfeited match, because your own money and the growth on both disappear with it. There is no other instrument offering a guaranteed 50% return on deposit.
Strengths & Limits Of This Model
Where this engine is strong
- Runs entirely in your browser — no figure you type is transmitted or stored.
- Shows the full working, so every number can be traced and challenged.
- Free, unmetered and free of affiliate incentives.
Where it stops
- Generalised assumptions cannot capture every individual circumstance.
- Jurisdiction-specific rules and mid-year changes may not be reflected.
- A model output is not a substitute for a professional review of your position.
Practical Use Cases
Checking you are capturing the full match
Set your contribution below the cap and watch the forfeited amount appear. Contributing at least to the cap is the highest-return decision available to most employees, ahead of debt repayment at anything below credit-card rates. Compare against the alternative with the Debt Payoff Calculator.
Understanding what a contribution really costs you
Because contributions are pre-tax, a $425 monthly contribution reduces take-home pay by roughly $323 at a 24% marginal rate. The engine reports that figure directly, which is usually the number that decides whether someone increases their rate. Model the paycheck effect with the Paycheck Calculator.
Deciding between a 401(k) and an IRA
Capture the full match first, since nothing else pays 50% on deposit, then compare the next dollar against an IRA on fees and fund choice. The IRA Calculator models the traditional-versus-Roth decision that follows.
Methodology & Editorial Standards
Contributions are modelled monthly on the assumption that salary and contribution rate hold constant in nominal terms, with growth applied on a monthly grid. The match is computed as the employer rate applied to the lesser of your contribution rate and the plan cap, which is the structure the large majority of US plans use; formulas with tiered or graded matches will differ. Statutory deferral limits are not enforced by the engine, since they change annually and vary with age. Projections are nominal and before any tax on withdrawal, and no vesting schedule is applied — unvested employer money is forfeited if you leave early. The engine implements the standard published formula for this calculation. Inputs are validated for domain and sign before evaluation, and any undefined case returns an em-dash rather than a spurious value.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
401k Calculator — 20 Expert FAQs
20 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How much is my employer match actually worth?
On these figures the employer pays in $63,750 over 25 years and it arrives at retirement as $172,140.23. That 2.70x multiple is time doing the work. It is the highest-certainty return available in personal finance.
What happens if I contribute below the match cap?
You forfeit employer money permanently — it does not accrue for later. Dropping from 6% to 3% here costs $258,210.35 at retirement, because you lose your own contribution, the match on it, and all the growth on both.
What does a '50% match up to 6%' mean?
The employer adds 50 cents for every dollar you contribute, but only counts contributions up to 6% of your salary. Contributing more than 6% is still sensible for other reasons, but it attracts no additional match.
How much does contributing actually reduce my pay?
Less than the contribution, because it comes out pre-tax. A $425 monthly contribution at a 24% marginal rate reduces take-home pay by about $323. The government funds the difference, which is the second large subsidy in the account after the match.
Is 7% a reasonable return assumption?
It is a common long-run nominal assumption for a diversified equity-heavy portfolio, but any particular 25-year window can differ substantially. Model 5% as well and plan against the more conservative figure.
What is vesting?
The schedule on which employer contributions become genuinely yours. Cliff vesting grants everything after a set period; graded vesting phases it in. Your own contributions are always immediately yours. This engine assumes full vesting.
Are there limits on how much I can contribute?
Yes — the IRS sets an annual elective deferral limit, with an additional catch-up allowance from age 50. The limits change most years, so check the current figures. The engine does not enforce them, so verify high contribution rates against the cap.
Should I choose a traditional or a Roth 401(k)?
The same logic as the IRA decision: traditional deducts now and taxes later; Roth does the reverse. If you expect a higher tax rate in retirement than today, Roth wins. Run the comparison on the IRA Calculator, which models both sides properly.
What happens to my 401(k) if I change jobs?
You can generally leave it, roll it into the new employer's plan, or roll it into an IRA. Rolling to an IRA usually widens fund choice and lowers fees; cashing out triggers tax and, before 59½, an additional penalty. Unvested employer money is lost.
Does this projection account for salary increases?
No — it holds salary constant in nominal terms, which is deliberately conservative. Real contributions usually rise with pay, so a plan that looks adequate here will often perform better. Do not rely on that as the plan.
Should I pay off debt or contribute to my 401(k)?
Contribute at least to the match cap first: a 50% match beats the interest rate on almost any debt. Above the cap, compare your expected return against the debt's rate, and clear anything above roughly 8-10% before investing more.
Are 401(k) fees worth worrying about?
Very much so. Plan administration plus fund expenses of 1% a year removes a large fraction of a long-horizon balance. Check your plan's fee disclosure, favour the lowest-cost index options, and model the drag with the Investment Calculator.
What is the difference between a 401(k) and an IRA?
A 401(k) is employer-sponsored, has much higher contribution limits and may carry a match, but offers whatever funds the plan chose. An IRA is yours, with a lower limit but unrestricted investment choice. Most people should use both.
When can I withdraw without penalty?
Generally from age 59½, with certain exceptions including separation from service at 55 or later under the rule of 55. Earlier withdrawals typically attract income tax plus a 10% additional tax, which together can remove a third of the amount.
Does the projection account for inflation?
No, it is nominal. At 3% inflation, $745,437.43 in 25 years has roughly the purchasing power of $356,000 today. Judge the adequacy of a retirement balance in today's money using the Inflation Calculator.
Is this 401k calculator free to use?
Yes. It is free, requires no account, and has no usage limits. ApexConverter is funded by contextual advertising, never by selling user data.
Is my data sent to a server?
No. The engine runs as Vanilla JavaScript inside your browser under our Zero-Server Client-Side Execution model. Your figures are computed locally and are never transmitted, logged, or stored.
How accurate is this calculator?
It applies the standard closed-form formula in IEEE-754 double precision, rounding only at the display layer. The engine is reconciled against an independent reference implementation before release.
Does it work on mobile?
Yes. The interface is mobile-first with numeric keypad hints and is tested down to a 320-pixel viewport with no horizontal scrolling.
Can I use it offline?
Largely, yes. Because computation is client-side, the page continues to calculate without a network connection once it has loaded.