Free Tax Calculator — Withholding Gap & 2026 Brackets

Last updated: April 17, 2026

MoneyMath's tax calculator estimates 2026 federal income tax, state tax, self-employment tax, child tax credits, and the gap between expected withholding and likely tax due.

Free to useRuns in your browserSource-backed assumptions

Estimate federal and state income tax using filing status, deductions, credits, and side income.

See marginal bracket effects so you can separate tax owed from your top tax rate.

Check withholding gaps before tax season instead of discovering the shortfall in April.

How to use this calculator

Step 1Enter your starting information. Add the core inputs requested by the Tax Calculator, such as amounts, dates, rates, income, weight, or other scenario details.
Step 2Review the calculated result. Read the headline answer first, then scan the supporting breakdown, chart, or comparison table.
Step 3Compare another scenario. Change one input at a time to understand what drives the result and which option is most realistic.

Formula, Sources & Assumptions

Formula

Estimated tax = federal bracket tax + state tax + self-employment tax - credits, compared with estimated withholding.

Assumptions

Federal brackets and standard deduction use tax year 2026 values.
Withholding is an estimate based on a simplified percentage-method model.
State tax estimates may not include every deduction, credit, local tax, or special filing rule.

Sources

IRS 2026 tax inflation adjustmentsFederal brackets, standard deduction, and indexed tax items.
SSA 2026 Social Security changesOASDI wage base and FICA context.
IRS 2026 retirement plan limits401(k), IRA, and catch-up contribution limits.
IRS Rev. Proc. 2025-19 HSA limits2026 HSA contribution limits and HDHP thresholds.