Your effective tax rate is everything you pay divided by everything you earn. It is the average across all of your income, and it answers a different question from the rate on the next pound or dollar: not what a raise is worth, but how much of the salary you have now ends up in tax.
In a banded system it is lower than the top tax bracket you reach, because the lower slices are taxed at less. A single American on $75,000 in 2026 pays $7,670 of federal income tax after the standard deduction, using the IRS 2026 thresholds. That is 10.2% of salary, although the last dollars are taxed at 22%. Add $5,737.50 of Social Security and Medicare at the IRS Topic 751 rates and the effective rate on all deductions is 17.9%.
Check the denominator before comparing two figures. The same $7,670 is 13.0% of taxable income and 10.2% of gross pay, and published statistics use both. Check the numerator too: some figures count income tax only, others include social contributions.
The marginal rate is the one to use for decisions at the edge, such as overtime or a pension contribution. The effective rate is the one to use for budgets and for comparing what the same salary is worth in two countries. The gap between them is not always in the same direction: above the US Social Security wage base the charge on the next dollar falls, and a tapering credit can push the marginal rate far above the average.
The take-home pay calculator reports the effective rate as total deductions divided by gross pay, beside the marginal rate, for every country it covers.