Taking money out of a 401(k) before retirement is taxed harder than almost any other account. A pre-tax distribution is added to your taxable income for the year (taxed at your marginal rate), and if you are under 59½ the IRS adds a 10% additional tax on the whole amount — unless an exception such as the rule of 55 applies. A 401(k) withdrawal calculator exists to make that stacked cost visible before you decide, not after.
This page models a single distribution from a pre-tax 401(k). Roth 401(k) qualified distributions are a different story (contributions and growth come out tax-free), and this tool deliberately does not model them.
How the tax and penalty stack
The calculator applies two charges in sequence. First, federal income tax: the withdrawal is treated as ordinary income, so you pay your marginal rate on the full amount. Second, the 10% additional tax under IRC §72(t) — this one is mechanical, owed on the entire distribution if you are younger than 59½, and it does not care what bracket you are in. State income tax, where it applies, stacks on top of both.
The rule of 55 is the biggest lever available to people leaving work mid-career: if you separate from service in or after the calendar year you turn 55, distributions from that employer's plan skip the 10% additional tax entirely. You still owe ordinary income tax, but the penalty side goes to zero. Toggle the field above to see the difference on your own numbers.
penalty = (age < 59.5 && !ruleOf55) ? amount × 10% : 0
tax = amount × federalTaxPct
net = amount − tax − penaltyThe effective rate row is the one to stare at: stacking a 22% bracket on top of a 10% penalty means roughly a third of the withdrawal never reaches you. That effective cost is why advisors treat an early 401(k) withdrawal as a last resort, behind loans, Roth contributions, and taxable savings.
The sample, end to end. You withdraw $200,000 at age 52 in a 22% bracket. Federal tax takes $44,000 and the 10% additional tax takes $20,000 — you keep $136,000, an effective haircut of 32%. Leave the same job at 55 with the rule of 55 on and the penalty vanishes: tax drops to $44,000 and you keep $156,000. Same money, $20,000 more in your pocket — that gap is the entire argument for waiting or planning the separation carefully.
Terms & definitions
Additional tax (penalty)
The 10% charge under IRC §72(t) on distributions before age 59½, on top of ordinary income tax. Waived for listed exceptions including the rule of 55.
Rule of 55
Penalty waiver when you separate from service in or after the calendar year you turn 55; applies only to that employer's plan, not IRAs.
SEPP / 72(t)
Substantially Equal Periodic Payments — a fixed withdrawal series that avoids the penalty but locks you in for 5+ years.
Marginal tax rate
The rate applied to your last dollar of income; pre-tax distributions stack on top of your salary, so this is the rate that applies.
Frequently asked questions
What is the rule of 55?
If you leave the job that holds your 401(k) in or after the calendar year you turn 55, distributions from that plan are exempt from the 10% additional tax. You still pay ordinary income tax. The rule applies per-plan: money still sitting in an older employer's plan or an IRA does not qualify — IRAs use age 59½ regardless. Public safety employees get a lower age (50). Set the rule-of-55 field to 1 above to see the effect.
What is a 72(t) / SEPP withdrawal?
Substantially Equal Periodic Payments under IRC §72(t)(2)(A)(iv) let you take penalty-free withdrawals before 59½, but you must take a fixed series for at least 5 years or until 59½ (whichever is longer), and modifying the schedule retroactively triggers the 10% tax on everything taken. This calculator models single distributions only — for SEPP, the obligation is the schedule, not the math.
Does the 10% penalty apply to Roth 401(k) withdrawals?
Qualified Roth 401(k) distributions — age 59½ plus a 5-year holding period — are tax-free and penalty-free. Non-qualified distributions have pro-rata rules: earnings are taxed and penalized, contributions come out first. This tool models pre-tax 401(k) distributions; if your money is Roth, the answer is usually "don't withdraw, let it grow tax-free."
Is cashing out a small 401(k) when changing jobs a big deal?
The amounts look small, so people cash out; the compounding they surrender is not small. A distribution also gets the stacked tax treatment above. The standard alternatives — rolling into the new employer's plan, an IRA rollover, or leaving it if fees are good — preserve the full balance and its growth.
References
- IRS — Retirement topics: tax on early distributions: irs.gov/retirement-plans/plan-participant-employee/retirement-topics-tax-on-early-distributions
- IRS Publication 575 — Pension and annuity income, IRC §72(t) exceptions: irs.gov/publications/p575
- Investor.gov — compound interest and retirement account fundamentals: investor.gov