{"tool":{"slug":"401k","name":"401k calculator","version":"2026-08-22","canonicalUrl":"https://carlo.finance/tools/401k","jsonUrl":"https://carlo.finance/tools/401k.json","pageUrl":"https://carlo.finance/tools/401k","parameters":[{"key":"salary","label":"Salary","unit":"usd-per-year","min":0,"max":100000000,"default":100000,"sourceId":null,"help":"Your gross pay before anything comes out. This is the offer-letter number, not box 1 of your W-2: the deferral below is what turns one into the other."},{"key":"contribution","label":"You contribute","unit":"percent","min":0,"max":100,"default":6,"sourceId":null,"help":"The percent of pay you defer into the plan each year, before tax. Capped at 23,500 a year by § 402(g), more once you turn 50."},{"key":"match","label":"Employer matches up to","unit":"percent","min":0,"max":100,"default":4,"sourceId":null,"help":"The percent of your pay your employer will match. Contributing less than this leaves money your employer already offered you, which is the most expensive mistake on this page."},{"key":"matchRate","label":"Match rate","unit":"percent","min":0,"max":300,"default":100,"sourceId":null,"help":"Cents your employer puts in per dollar you put in, up to the percent above. 100 is dollar for dollar; 50 is the common half match."},{"key":"age","label":"Your age","unit":"years","min":16,"max":79,"default":35,"sourceId":null,"integer":true,"help":"Sets how long the money compounds, whether you get a catch-up contribution, and whether the deferral earns the § 25B saver's credit."},{"key":"retireAge","label":"Retiring at","unit":"years","min":17,"max":80,"default":65,"sourceId":null,"integer":true,"help":"The age you stop contributing and look at the balance. Every extra year here adds a contribution and a year of compounding on everything before it."},{"key":"balance","label":"Current balance","unit":"usd","min":0,"max":100000000,"default":0,"sourceId":null,"help":"What is in the account today, including anything you rolled in. It compounds alongside the new contributions."},{"key":"rate","label":"Annual return","unit":"percent","min":0,"max":20,"default":7,"sourceId":null,"help":"The yearly growth you assume, before fees and before tax on withdrawal. This is an assumption you choose, not a forecast, and it moves the answer more than anything else here."}],"options":[{"key":"status","label":"Filing status","options":[{"value":"single","label":"Single"},{"value":"married-joint","label":"Married filing jointly"},{"value":"married-separate","label":"Married filing separately"},{"value":"head-of-household","label":"Head of household"},{"value":"qualifying-surviving-spouse","label":"Qualifying surviving spouse"}],"default":"single","sourceId":null,"help":"Your status on the last day of the year. It does not change what goes into the account, only what the contribution saves you in tax this year."}]},"taxYear":2025,"inputs":{"salary":100000,"contribution":6,"match":4,"matchRate":100,"age":35,"retireAge":65,"balance":0,"rate":7,"status":"single"},"result":{"endBalance":1016642.5,"taxSaved":1320,"years":30,"startingBalance":0,"yourTotal":180000,"matchTotal":120000,"growthTotal":716642.5,"yearly":[{"year":1,"age":36,"yours":6000,"employer":4000,"growth":327.15,"balance":10327.15},{"year":2,"age":37,"yours":6000,"employer":4000,"growth":1073.71,"balance":21400.86},{"year":3,"age":38,"yours":6000,"employer":4000,"growth":1874.22,"balance":33275.08},{"year":4,"age":39,"yours":6000,"employer":4000,"growth":2732.61,"balance":46007.7},{"year":5,"age":40,"yours":6000,"employer":4000,"growth":3653.05,"balance":59660.75},{"year":6,"age":41,"yours":6000,"employer":4000,"growth":4640.03,"balance":74300.79},{"year":7,"age":42,"yours":6000,"employer":4000,"growth":5698.36,"balance":89999.15},{"year":8,"age":43,"yours":6000,"employer":4000,"growth":6833.2,"balance":106832.35},{"year":9,"age":44,"yours":6000,"employer":4000,"growth":8050.07,"balance":124882.42},{"year":10,"age":45,"yours":6000,"employer":4000,"growth":9354.91,"balance":144237.34},{"year":11,"age":46,"yours":6000,"employer":4000,"growth":10754.08,"balance":164991.42},{"year":12,"age":47,"yours":6000,"employer":4000,"growth":12254.4,"balance":187245.82},{"year":13,"age":48,"yours":6000,"employer":4000,"growth":13863.17,"balance":211108.99},{"year":14,"age":49,"yours":6000,"employer":4000,"growth":15588.24,"balance":236697.23},{"year":15,"age":50,"yours":6000,"employer":4000,"growth":17438.02,"balance":264135.25},{"year":16,"age":51,"yours":6000,"employer":4000,"growth":19421.51,"balance":293556.76},{"year":17,"age":52,"yours":6000,"employer":4000,"growth":21548.4,"balance":325105.16},{"year":18,"age":53,"yours":6000,"employer":4000,"growth":23829.03,"balance":358934.19},{"year":19,"age":54,"yours":6000,"employer":4000,"growth":26274.54,"balance":395208.72},{"year":20,"age":55,"yours":6000,"employer":4000,"growth":28896.83,"balance":434105.55},{"year":21,"age":56,"yours":6000,"employer":4000,"growth":31708.68,"balance":475814.23},{"year":22,"age":57,"yours":6000,"employer":4000,"growth":34723.8,"balance":520538.03},{"year":23,"age":58,"yours":6000,"employer":4000,"growth":37956.89,"balance":568494.92},{"year":24,"age":59,"yours":6000,"employer":4000,"growth":41423.7,"balance":619918.62},{"year":25,"age":60,"yours":6000,"employer":4000,"growth":45141.12,"balance":675059.74},{"year":26,"age":61,"yours":6000,"employer":4000,"growth":49127.28,"balance":734187.02},{"year":27,"age":62,"yours":6000,"employer":4000,"growth":53401.59,"balance":797588.62},{"year":28,"age":63,"yours":6000,"employer":4000,"growth":57984.9,"balance":865573.52},{"year":29,"age":64,"yours":6000,"employer":4000,"growth":62899.53,"balance":938473.05},{"year":30,"age":65,"yours":6000,"employer":4000,"growth":68169.45,"balance":1016642.5}],"deferral":6000,"requestedDeferral":6000,"deferralLimit":23500,"catchUp":0,"employerFirstYear":4000,"totalFirstYear":10000,"consideredPay":100000,"taxWithout":13455,"taxWith":12135,"saversCredit":0,"netCost":4680,"savingRate":22,"firstDollarRate":22,"otherTaxes":0,"otherTaxesWithout":0,"matchLeftOnTable":0,"matchLeftOnTableAtRetirement":0,"computability":{"status":"final","fileReady":true,"blocking":[]}},"drivers":[{"key":"rate","label":"Assumed return","step":1,"balanceDelta":225323.71,"sentence":"One more point of annual return, 8% instead of 7%, ends with $225,324 more. This is an assumption, not a decision you get to make."},{"key":"contribution","label":"Contribution rate","step":1,"balanceDelta":101664.25,"sentence":"Deferring one more percent of pay, $1,000 a year, ends with $101,664 more."},{"key":"retireAge","label":"One more year","step":1,"balanceDelta":83820.32,"sentence":"Working one more year to 66 ends with $83,820 more: one extra contribution, plus a year of growth on everything already there."}],"sensitivity":{"byContribution":[{"contribution":0,"deferral":0,"employer":0,"endBalance":0,"taxSaved":0},{"contribution":3,"deferral":3000,"employer":3000,"endBalance":609985.5,"taxSaved":660},{"contribution":4,"deferral":4000,"employer":4000,"endBalance":813314,"taxSaved":880},{"contribution":6,"deferral":6000,"employer":4000,"endBalance":1016642.5,"taxSaved":1320},{"contribution":10,"deferral":10000,"employer":4000,"endBalance":1423299.5,"taxSaved":2200},{"contribution":15,"deferral":15000,"employer":4000,"endBalance":1931620.74,"taxSaved":3300}],"byRate":[{"rate":4,"endBalance":578374.5},{"rate":5,"endBalance":693548.86},{"rate":6,"endBalance":837095.87},{"rate":7,"endBalance":1016642.5},{"rate":8,"endBalance":1241966.21},{"rate":9,"endBalance":1525619.57},{"rate":10,"endBalance":1883739.94}],"byStatus":[{"status":"single","label":"Single","taxSaved":1320},{"status":"married-joint","label":"Married filing jointly","taxSaved":720},{"status":"married-separate","label":"Married filing separately","taxSaved":1320},{"status":"head-of-household","label":"Head of household","taxSaved":1320},{"status":"qualifying-surviving-spouse","label":"Qualifying surviving spouse","taxSaved":720}]},"limits":{"electiveDeferral":23500,"catchUp50":7500,"catchUp60to63":11250,"compensation":350000,"annualAdditions":70000,"sourceId":"notice-2024-80"},"assumptions":[{"key":"salary","label":"Salary","value":100000,"unit":"usd-per-year","provided":false,"source":null},{"key":"contribution","label":"You contribute","value":6,"unit":"percent","provided":false,"source":null},{"key":"match","label":"Employer matches up to","value":4,"unit":"percent","provided":false,"source":null},{"key":"matchRate","label":"Match rate","value":100,"unit":"percent","provided":false,"source":null},{"key":"age","label":"Your age","value":35,"unit":"years","provided":false,"source":null},{"key":"retireAge","label":"Retiring at","value":65,"unit":"years","provided":false,"source":null},{"key":"balance","label":"Current balance","value":0,"unit":"usd","provided":false,"source":null},{"key":"rate","label":"Annual return","value":7,"unit":"percent","provided":false,"source":null},{"key":"status","label":"Filing status","value":"single","unit":"choice","provided":false,"source":null}],"sources":[{"id":"notice-2024-80","name":"IRS Notice 2024-80 (2025 amounts relating to retirement plans)","url":"https://www.irs.gov/pub/irs-drop/n-24-80.pdf","asOf":"2024-11-01","note":"The elective deferral limit, the age 50 and age 60 to 63 catch-up amounts, the annual compensation limit, and the annual additions limit for 2025. These are the same figures the tax engine's parameter index carries, and a test pins every constant in this file against it."},{"id":"rev-proc-2024-40","name":"IRS Rev. Proc. 2024-40 (2025 inflation-adjusted items)","url":"https://www.irs.gov/pub/irs-drop/rp-24-40.pdf","asOf":"2024-10-22","note":"The ordinary income rate tables (§ 2.01) the engine applies when it computes the return twice to measure what the deferral saves."},{"id":"pl-119-21-obbba","name":"Public Law 119-21 § 70102 (2025 standard deduction)","url":"https://www.congress.gov/bill/119th-congress/house-bill/1/text","asOf":"2025-07-04","note":"The 2025 standard deduction the engine actually applies, which this statute raised after Rev. Proc. 2024-40 had set it. Both returns start from that figure, so it is what decides whether a deferral saves anything at all at low income."},{"id":"usc-title-26","name":"26 U.S.C. (Internal Revenue Code)","url":"https://uscode.house.gov/browse/prelim@title26","asOf":"2026-04-21","note":"The sections these limits come from: § 402(g)(1) elective deferrals, § 414(v) catch-up contributions, § 401(a)(17) compensation, § 415(c) annual additions, and § 25B the saver's credit, whose 10, 20 and 50 percent rates the engine also reads from here."}],"warnings":[],"disclaimer":"This projects a traditional pre-tax 401(k) using tax year 2025 contribution limits held flat, and measures the federal income tax this year's deferral saves by running the return twice. Every figure is in today's dollars with no raises and no inflation. It is not a Roth 401(k), it excludes state tax, Social Security and Medicare tax, plan fees, vesting schedules, and the tax you will owe when you withdraw, and the return you enter is an assumption rather than a forecast. Nothing here is tax or investment advice."}