Payroll Tax Calculator

The Payroll Tax Calculator covers the two taxes that share the name on opposite sides of the Pacific: US FICA (Social Security and Medicare, employee and employer shares) computed from gross pay and pay frequency, and Australian state payroll tax computed from a state's threshold and rate on annual wages. Select the system you mean; the arithmetic for each is below.

US mode: how it works

Pay is annualized by the pay period (weekly x52, bi-weekly x26, semi-monthly x24, monthly x12), Social Security is charged at 6.2% up to the calculator's stored wage base of $168,600, Medicare at 1.45$200,000, and the annual figures are divided back into per-period amounts. The employer matches Social Security and standard Medicare but never pays the additional 0.9%.

$\text{Employee FICA per period}=\frac{\min(\text{Annual pay},\ 168{,}600)\times 6.2\%+\text{Annual pay}\times 1.45\%+\text{Add'l Medicare}}{\text{Periods per year}}$

US worked example

Gross pay of $2,000 bi-weekly annualizes to$52,000. Social Security is $52,000 x 6.2$3,224 a year, Medicare is $52,000 x 1.45$754, so employee FICA is $124.00 +$29.00 = $153.00 per period** and take-home before income tax is **$1,847.00. The employer pays the same $153.00 again (its cost of employing is$2,153 per period before benefits), and combined FICA on the year is $7,956. Watch the wage base in action at higher pay: at$200,000 a year, Social Security stops at $168,600 x 6.2$10,453.20 while Medicare continues, which is why high earners see their per-period FICA drop partway through the year.

Australian mode: how it works

Enter annual wages and a state, and the calculator applies that state's stored threshold and headline rate to the excess: NSW $1,200,000 at 5.45$900,000 at 4.85%, Queensland $1,300,000 at 4.75$1,000,000 at 5.5%, South Australia $1,500,000 at 4.95$1,250,000 at 4.0%, the ACT $2,000,000 at 6.85$1,500,000 at 5.5%. It reports taxable wages, the annual and monthly tax, whether registration is required, and the effective rate on total wages. A New South Wales wage bill of $2,000,000 owes tax on$800,000 of excess: $43,600 a year (about$3,633 a month), an effective rate of 2.18%. The companion reference, Payroll Tax Rates Australia 2026 on this site, explains what counts as wages and how multi-state employers apportion the threshold.

What neither mode includes

The US mode is FICA only: no federal or state income-tax withholding, no pretax deductions (401(k), health premiums, HSAs change both taxable wages and take-home), no employer FUTA or state unemployment insurance, and its wage base is the stored figure described above rather than a promise about the current year's IRS limit, so verify before running live payroll. The Australian mode applies the headline rate to the full excess; real assessments layer in tiered rates or surcharges for very large employers in some states, pro-rated thresholds for part-year and grouped employers, and exemptions (apprentices, leave wages) that the headline arithmetic does not model. Both modes are estimates for planning.

Frequently Asked Questions

Why does my take-home drop less than my FICA in January?

Because of the Social Security wage base: once cumulative wages pass the cap mid-year, the 6.2% stops and only Medicare continues, then the cap resets in January and the full FICA returns. The calculator's per-period figures are the even average across the year; your actual payslips step down when you cross the base.

Who pays the additional 0.9% Medicare tax?

Employees only, on wages above the threshold ($200,000 in the calculator's single-filer model; the real threshold varies by filing status). Employers neither pay nor match it, though they must withhold it once an employee's wages with them pass$200,000.

Is Australian payroll tax deducted from employees' pay?

Never. It is the employer's own state tax on its total wage bill once the threshold is passed, which is why it is computed on annual wages for the whole business rather than per payslip.