How sales tax is worked out
Sales tax is a percentage of the price, added on at the till rather than folded into the sticker price. Multiply the pre-tax price by the rate, and add that figure back onto the price.
A $100 item taxed at 8.875%, a real combined rate used in parts of New York City, comes to $8.875 of tax before rounding, which lands on $8.88 to the cent and a total of $108.88. Change the rate and both figures move with it; the arithmetic never changes, only the number you feed into it.
Working backwards from a receipt total
Sometimes the number in front of you is the total, not the price: a card statement, a quoted job cost, a receipt where only the bottom line survived. The instinct is to take the tax rate off that total directly, and it is the single most common sales tax mistake there is, because the rate was never charged against the total in the first place. It was charged against the smaller pre-tax price, so pulling it back out means dividing, not subtracting.
Take a $108 total taxed at 8%. Subtract 8% of $108 (that is $8.64) and you get $99.36, which looks plausible and is wrong. Divide $108 by 1.08 instead and the correct pre-tax price appears: exactly $100.00, with $8.00 of tax. The gap between $99.36 and $100.00 is only 64 cents here, but it grows with the rate and the total, and it is always in the same direction: subtracting overstates the tax and understates the price. The calculator's back-out mode does the division for you and shows the same comparison with your own numbers.
Why the rate on your receipt is never one number
Sales tax in the United States is layered: a statewide rate, then a county or city rate stacked on top, sometimes a special district rate on top of that. Two shops a few miles apart, in different counties, can legitimately charge different combined rates on an identical item, which is why this page will not print a state-by-state table. Any single number goes stale the moment a city council changes a local rate, and by the time it is out of date it is actively misleading rather than just old. What stays true is the shape of the system: check the combined rate for the specific address where the sale happens, rather than assuming a state-level figure covers it.
Five states charge no statewide sales tax at all: Alaska, Delaware, Montana, New Hampshire and Oregon. Even there the picture is not always simple; Alaska and Montana both allow local jurisdictions to levy their own sales taxes, so a purchase can still carry tax despite the state itself charging none. Everywhere else, the rate printed on a receipt is a combined figure, and the only reliable way to know it is to check it for that address rather than guess from the state name alone.
Readers outside the US meet the same arithmetic under a different name. Value-added tax, the consumption tax used across the UK and the EU, is added and removed with exactly the same multiply-and-divide relationship as sales tax; only the way it is administered differs, since VAT is usually built into the shelf price rather than added at the till. The two modes on this page work identically whichever percentage-based tax you are dealing with.
Choosing the right mode and rate
Use "add tax to a price" whenever you are starting from a price tag, a quote, or a subtotal that has not been taxed yet, and want to know what you will actually be charged. Use "back tax out of a total" whenever the number in hand already includes tax, such as a card statement, an expense report, or a receipt where you only have the final figure and need the underlying price for accounting or reimbursement. The rate itself should come from the receipt or the point of sale wherever possible; typing a rounded guess such as "about 8%" when the real combined rate is 8.875% will throw the total off by real money on a large purchase, even though it looks like a trivial difference per dollar.
Reading the chart and the table
The donut splits the total into price and tax by size, so you can see at a glance how much of what you are paying is the item itself against how much is tax on top. The table beside it holds the same pre-tax price steady and reruns it at several other illustrative rates, including whichever rate you actually entered if it is not already one of the presets, so you can compare what the identical purchase would cost somewhere with a different combined rate.
Questions people ask
How do I calculate sales tax backwards from a total?
Divide the total by one plus the tax rate as a decimal, not by subtracting the rate from the total. A $108.88 total at 8.875% divides by 1.08875 to give a $100.00 pre-tax price, with $8.88 of tax. Subtracting the percentage directly gives a lower, wrong price every time.
Which US states have no sales tax?
Alaska, Delaware, Montana, New Hampshire and Oregon charge no statewide sales tax. Alaska and Montana still allow local areas to charge their own sales tax, so a purchase in those two states is not automatically tax-free.
Why is the rate a decimal like 8.875% instead of a round number?
Because it is usually several taxes stacked together: a state rate plus a county rate plus, in some cities, a district rate on top of that. The combined figure rarely lands on a whole number, which is exactly why this calculator accepts decimals rather than rounding you to the nearest percentage point.
Is sales tax the same as VAT?
They are both percentage taxes on a sale and use the same maths to add or remove, but they are administered differently. Sales tax in the US is usually added at the till on top of a pre-tax price; VAT in the UK and the EU is normally already folded into the shelf price you see. Adding or backing tax out works the same way in both cases.
Does every state tax every purchase the same way?
No. Groceries, prescription medicine and clothing are commonly taxed at a reduced rate or exempted entirely in specific states, and services are taxed inconsistently from one state to the next. The combined rate you enter here should be the one that actually applies to the item and the address in question, not a general assumption.
Why might my receipt show a slightly different tax amount than this calculator?
Most likely rounding on a multi-item receipt, where tax is calculated per line or per department rather than once on the final subtotal, which can land a cent or two away from calculating it on the total in one pass. A different combined rate at the point of sale than the one typed in here would also explain a larger gap.
This calculator applies a single combined rate you provide; it does not look up rates by address, apply category exemptions, or account for tax holidays. Treat the result as arithmetic on the rate you enter, and confirm that rate against the receipt or the point of sale for anything that matters financially.