How do I find the tax if I only have the total?

Set the mode to "Total including tax". The calculator divides by (1 + rate) instead of multiplying, which is the only way to get the pre-tax price right.

Why not just take the percentage off the total?

Because the tax was calculated on the smaller pre-tax price. Taking the rate off the total overstates the tax — the higher the rate, the bigger the error.

Does this work for VAT or GST?

Yes. The arithmetic is identical — only the name and the rate change. Enter your VAT or GST rate and use the same two modes.

Why is there no list of state rates?

Because it would be wrong within months. Rates change and combine at state, county and city level. Look up your current combined rate and enter it here.

Everyday & Money

Sales Tax Calculator

Add tax to a price, or run it backwards: give it a receipt total and it tells you how much of it was tax. Works with any rate — US state and local sales tax, VAT or GST.

Your numbers

Result

Total with tax

$108.25

Sales tax

$8.25

Price before tax: $100.00

Breakdown
Item	Amount
Price before tax	$100.00
Sales tax (8.25%)	$8.25
Total with tax	$108.25

Adding tax to a price

Straightforward: tax = price × rate, and total = price + tax. A $100 item at 8.25% carries $8.25 of tax and rings up at $108.25.

Working backwards from the total

This is the one people get wrong. If a receipt says $108.25 including 8.25% tax, you cannot just take 8.25% of $108.25 — that gives $8.93, which is too much. The tax was charged on the pre-tax price, not the total. The right move is to divide: price before tax = total ÷ (1 + rate) So 108.25 ÷ 1.0825 = 100.00, and the tax was $8.25. Switch the mode field to run it this way.

Which rate should you use?

Whichever applies to you — that is why this calculator does not ship a rate table. In the US, sales tax is set by state and often stacked with county and city rates, so two shops a few miles apart can charge differently; five states charge no state sales tax at all. VAT and GST rates are national. Check your local rate and enter it.

Frequently asked questions

Sources

Tax Foundation — State and local sales tax rates
OECD — Consumption tax trends (VAT/GST rates)

Embed this calculator

Copy the code and paste it into your site or blog. Credit with a link back to Contania is included, and the height adjusts itself.

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