Income Tax Calculator

The Income Tax Calculator estimates income tax and after-tax income under four national systems, the United States, United Kingdom, Australia, and Canada (federal), applying each system's stored progressive brackets to your income and deductions, and reporting taxable income, tax owed, the effective and marginal rates, a bracket-by-bracket breakdown, and social contributions where the model includes them (UK National Insurance, the Australian Medicare levy).

How It Works

Taxable income is gross income minus the deductions entered (or the system's built-in personal allowance where the model supplies one), and the brackets then tax each slice of income at its own rate:

$\text{Tax}=\sum_{\text{brackets}}\big(\text{Income slice in bracket}\times\text{Bracket rate}\big)$

The marginal rate is the rate on your highest slice; the effective rate is total tax divided by gross income. Those two numbers answer different questions, and the calculator reports both deliberately.

Parameters

| Input | Required | Meaning | |---|---|---| | Gross income | Yes | Annual earnings before tax | | Country | Yes | US, UK, AU, or CA (federal) | | Filing status | US | Single, married jointly/separately, head of household | | Tax year | US | 2024 or 2025 stored tables | | Deductions | No | Amounts reducing taxable income |

Worked examples, one per system

United States (2025, single): income $85,000 with the$15,750 standard deduction entered gives taxable income of $69,250. The brackets charge 10$11,925 ($1,192.50), 12$36,550 ($4,386), and 22$20,775 ($4,570.50): total tax **$10,149**, after-tax income $74,851, an effective rate of 11.9% against a marginal rate of 22%.

United Kingdom (2025/26): income £60,000. The £12,570 personal allowance leaves £47,430 taxable: 20% on £37,700 (£7,540) and 40% on £9,730 (£3,892) give income tax of £11,432. National Insurance adds 8% between £12,570 and £50,270 (£3,016) plus 2% above (£194.60), £3,210.60 in all, for a total liability of £14,642.60 and take-home of £45,357.40.

Australia: income A$100,000 under the stored Stage 3 scale pays nothing on the first$18,200, 16% to $45,000 ($4,288), and 30% to $135,000 ($16,500): tax of **A$20,788**, plus the model's Medicare levy of 2$2,000), totalling A$22,788** and leaving **A$77,212.

Canada (federal): income CA$90,000 with the basic personal amount of$16,129 deducted leaves $73,871 taxable: 14.5$57,375 ($8,319.38) and 20.5$16,496 ($3,381.68) give federal tax of about **CA$11,701**, before any provincial tax, which this model does not include.

Reading marginal versus effective, and the deduction field

The worked examples make the standard confusion visible: the US taxpayer is "in the 22% bracket" yet pays 11.9% of gross income overall, because most dollars were taxed at 10% and 12% and the first $15,750 at nothing. A raise is taxed at the marginal rate only on the dollars inside the top bracket, which is why a raise can never reduce take-home pay under a progressive system. The deductions field deserves the same care: in the US model it is your only shield (enter the standard deduction for your status and year,$14,600 single in 2024 or $15,750 in 2025, or your itemized total if larger), while the UK model applies its personal allowance automatically when no deduction is entered, including the taper that withdraws £1 of allowance per £2 of income over £100,000, an effect that creates a famously steep effective marginal rate in that band that the breakdown table lets you see forming.

What differs between the four models

The US model is federal income tax only: no state tax, no FICA payroll taxes, no credits. The UK model is the most complete of the four, pairing income tax with employee National Insurance as described. The Australian model applies its stored Stage 3 resident scale plus a simplified Medicare levy (2% once taxable income passes the model's threshold; the real levy has shade-in ranges and exemptions) and omits offsets such as LITO and private-health surcharges. The Canadian model is federal only, treating the basic personal amount as a deduction in a simplified way, and omits provincial tax, CPP, and EI entirely, so Canadian results understate the true total materially and should be read as the federal component alone. Country-specialized calculators on this site (the USA Paycheck Calculator, the AU Net Income Calculator) go deeper for their own systems.

Limitations

Planning estimates from stored tables: US 2024/2025, UK 2025/26, the Australian Stage 3 scale, and Canadian federal 2025. No credits, offsets beyond those described, capital-gains regimes, or sub-national taxes except as stated. Filing-status subtleties, residency rules, and income types beyond salary all move real liabilities. Verify with the relevant authority (IRS, HMRC, ATO, CRA) or a tax professional for decisions.

Frequently Asked Questions

Why is my effective rate so much lower than my bracket?

Because brackets are slices, not a flat rate on everything. Your highest rate touches only the top slice of income; the effective rate averages all the lower slices and the untaxed allowance, and the calculator shows both because each is the right answer to a different question.

Which deductions should I enter for the US?

At minimum the standard deduction for your filing status and year if you do not itemize (entered in the worked example). If you itemize above that figure, enter the itemized total instead. Entering zero models a taxpayer with no deduction at all, which almost nobody is.

Does the calculator prepare or file a return?

No. It estimates a liability for planning, salary negotiation, and withholding sanity checks. A return involves credits, income types, and forms far beyond this model.