Sales Tax Calculator — add or remove tax from any amount
Add tax to a net figure or extract it from a gross one, with both directions shown.
Free and instant — results appear in seconds. No sign-up, no limits, and nothing you type is stored.
Adding tax and removing tax are different calculations, and reversing one with the other produces a wrong answer that looks plausible.
Adding is straightforward: multiply by the rate and add. Removing requires division, because the tax is a proportion of the net amount, not of the gross.
Choose the direction above and the calculator shows net, tax and gross together so the relationship is visible.
Why subtracting the percentage is wrong
An invoice arrives for 11,800 including 18% tax. What was the net amount?
The instinct is to take 18% off: 11,800 × 0.82 = 9,676. That is wrong.
The correct calculation divides:
net = gross ÷ (1 + rate)
= 11,800 ÷ 1.18
= 10,000.00Net (excluding tax) 10,000.00
Tax at 18.00% 1,800.00
Gross (including tax) 11,800.00
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The difference — 324 — arises because 18% of the net is 1,800, while 18% of the gross is 2,124. Tax is charged on the net figure, so working backwards requires division rather than subtraction.
This error compounds across a set of invoices and shows up as a reconciliation gap that is tedious to trace.
Add versus remove
Adding: gross = net × (1 + rate)
Removing: net = gross ÷ (1 + rate)
The two are inverses. Subtracting the percentage from the gross is not the inverse of adding it and never gives the right answer.
Inclusive and exclusive pricing
Whether displayed prices include tax is usually a legal requirement rather than a choice, and it varies by jurisdiction and by whether you sell to consumers or businesses. Many regions require consumer-facing prices to be shown inclusive.
Getting this wrong on a storefront produces either an unpleasant surprise at checkout or a shortfall you absorb yourself.
Rounding
Round at the line level or the invoice level consistently, and follow whatever your jurisdiction requires. Half-up is the common convention. Inconsistent rounding across an order produces totals that differ by a unit or two from what an accountant expects, and reconciling those is disproportionately painful.
Frequently asked questions
How do I remove tax from a gross amount?
Divide by one plus the rate as a decimal. To remove 18% from 11,800: 11,800 divided by 1.18 gives 10,000. Subtracting 18% from the gross gives 9,676, which is wrong, because the tax was calculated on the net figure rather than the gross.
Why is subtracting the percentage wrong?
Because the tax was a percentage of the net amount, not of the gross. Eighteen percent of the net is a smaller number than eighteen percent of the gross, so subtracting from the larger figure removes too much.
Should my displayed prices include tax?
That is usually set by law rather than preference, and it depends on your jurisdiction and whether you sell to consumers or businesses. Many regions require consumer-facing prices to be shown inclusive of tax. Check your local requirement rather than following a competitor.
Does this handle compound taxes?
No. It applies a single rate. Where two taxes stack and one is charged on the total including the other, calculate them in sequence, using the gross from the first step as the input to the second.
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