Our Methodology

MyTaxCalcs is built on a simple principle: you should never have to take our word for a tax number. Every calculator uses standard, publicly documented formulas drawn directly from IRS publications and official state agencies — no proprietary "black box" math. This page explains the sources we rely on, how each calculator is built, how often we update the figures, and the limitations you should know about before you rely on a result.

Where Our Numbers Come From

Tax figures on this site trace back to primary, authoritative sources rather than to other calculators or secondary summaries:

• Federal tax brackets and thresholds come from the IRS Revenue Procedures published each fall (for example, the Revenue Procedure that sets inflation-adjusted 2025 tax-year figures).
• Standard deduction amounts are taken from the IRS annual inflation-adjustment announcements.
• Self-employment tax follows IRS Schedule SE methodology and the Social Security Administration’s annual wage base.
• Capital gains rates and breakpoints use the IRS-published 0%, 15%, and 20% thresholds, which are adjusted annually for inflation.
• FICA and payroll figures come from the statutory Social Security and Medicare rates and the current Social Security wage base.
• State income tax data is sourced from each state’s Department of Revenue (or equivalent agency), not from third-party aggregators.

Where practical, individual calculator and reference pages link out to the specific IRS publication, Revenue Procedure, or state agency page the data came from, so you can verify it yourself.

How Each Calculator Is Built

Each tool applies the same math a tax professional would, in the open:

• Federal income tax is computed bracket by bracket — your taxable income is reduced by the standard deduction (or itemized total) for your filing status, then each portion is taxed at its marginal rate. We show both the effective rate and the marginal rate so the difference is clear.
• Tax refund estimates compare your projected total tax liability against the amount withheld or paid, so you can see whether you are likely to owe or receive money back.
• Self-employment tax applies the 15.3% combined Social Security and Medicare rate to 92.35% of net self-employment earnings, caps the Social Security portion at the annual wage base, adds the 0.9% Additional Medicare Tax where it applies, and shows the deductible one-half of SE tax.
• Capital gains tax separates short-term gains (taxed as ordinary income) from long-term gains (taxed at 0%, 15%, or 20% depending on taxable income), and flags where the 3.8% Net Investment Income Tax may apply.
• Sales tax combines the state base rate with local rates for a blended figure by jurisdiction.
• Payroll tax estimates take-home pay by applying federal withholding assumptions plus the 6.2% Social Security and 1.45% Medicare employee shares (with the 0.9% surtax above the threshold).
• State income tax pages apply each state’s own structure — graduated brackets, a flat rate, or no state income tax at all for the nine states without one.

Tax Year vs. Calendar Year

Tax figures are tied to a tax year, not the calendar date you happen to visit. A calculator labeled “2025” uses the brackets and deductions that apply to income earned in the 2025 tax year (the return most people file in early 2026). When we publish figures for an upcoming year before the IRS finalizes them, we label them as projected and replace them with official numbers once the relevant Revenue Procedure is released. Where a page offers both, we cross-link the 2025 and 2026 versions so you can pick the one that matches your situation.

How Often We Update

Tax brackets, standard deductions, contribution limits, and wage bases change every year. We refresh our calculators and reference pages each fall when the IRS publishes new inflation-adjusted figures, and again mid-year whenever legislation changes the rules — as happened with the tax provisions enacted in 2025. Reference pages carry a “Last updated” date so you can see how current the figures are.

What We Intentionally Simplify

Our calculators are estimation tools, and clarity sometimes means leaving out edge cases that apply to a small share of filers. Depending on the tool, results may not fully account for the Alternative Minimum Tax, every credit and its phase-out, local (city or county) income taxes, state-specific deductions and adjustments, employer-side payroll taxes, or unusual income types. When a factor is excluded, we aim to say so on the page. For anything beyond a general estimate — especially a complex return — the numbers here are a starting point, not a substitute for a full tax preparation.

Rounding and Assumptions

Results are typically rounded to the nearest dollar for readability, which can produce small differences from a return calculated to the cent. Unless you specify otherwise, calculators assume standard filing scenarios (for example, the standard deduction rather than itemizing). Any assumption that materially affects the result is stated alongside the inputs.

Accuracy and Corrections

We test each calculator against worked examples from official IRS instructions and re-verify the underlying figures whenever the source data changes. If you believe a number is wrong, we want to know — you can reach us through our contact page, and we correct confirmed errors promptly. For more on how we source, review, and correct our content, see our editorial standards.

MyTaxCalcs is part of a small, independently built family of free financial calculator sites, not affiliated with any financial institution, insurance company, or tax preparation service. You can see the full network on our About page.

Last updated: July 2026 · Maintained by De Van Do, Founder