Sales tax is charged on the price before tax, at a rate that is usually made of four separate layers: state, county, city and one or more special districts. Two addresses a mile apart can pay rates half a percent apart.
Total with 7.5% sales tax
$107.50
$100 of goods plus $7.50 of sales tax
| Jurisdiction | Rate | Tax on this sale |
|---|---|---|
| State | 6% | $6.00 |
| County | 1% | $1.00 |
| City | 0.5% | $0.50 |
| Combined | 7.5% | $7.50 |
Every layer is charged on the same pre-tax base, so the rates add up rather than compounding on each other.
| Rate | Tax | You pay |
|---|---|---|
| 0% | $0.00 | $100.00 |
| 4% | $4.00 | $104.00 |
| 5% | $5.00 | $105.00 |
| 6% | $6.00 | $106.00 |
| 7% | $7.00 | $107.00 |
| 7.25% | $7.25 | $107.25 |
| 8% | $8.00 | $108.00 |
| 8.875% | $8.88 | $108.88 |
| 9% | $9.00 | $109.00 |
| 10% | $10.00 | $110.00 |
Combined US rates mostly land between 6% and 9%. Exemptions depend on the item, so a rate is only a check on the receipt, never a substitute for it.
This calculator adds those layers to a price, reverse-engineers the tax out of a total that already includes it, and shows the same purchase at a range of common rates so you can sanity-check a receipt.
Total = price x (1 + rate / 100). A $100 purchase at a combined 7.5% is $107.50, of which $7.50 is tax. Each jurisdiction is applied to the same pre-tax base, so the layers add up rather than compounding.
Quantity matters when you buy several of the same item: the tax is computed on the extended price, which is what the calculator does when you enter a quantity.
If the price you have already includes tax, the pre-tax amount is total / (1 + rate / 100). At 7.5%, a $107.50 total holds $7.50 of tax because $107.50 / 1.075 = $100.
The common mistake is multiplying the total by the rate, which overstates the tax: 7.5% of $107.50 is $8.06, not $7.50. Tax is always a percentage of the pre-tax amount.
State sales tax exists in all but five states: Alaska, Delaware, Montana, New Hampshire and Oregon have no statewide sales tax, though Alaska allows local rates. On top of the state rate, counties, cities and special districts (transit, school, stadium, tourism) add their own.
Some states then apply local rates at the state level rather than per city, and a few tax only specific goods. That is why the rate on a receipt is the only authority for a particular purchase.
Most states exempt food bought at a grocery store, prescription medicine and some clothing, often up to a price cap per item. Services are taxed in some states and not in others, which is why two invoices for the same work can differ.
If you buy online, tax depends on the seller having a physical or economic presence in your state. After the economic nexus rules that followed the 2018 South Dakota decision, most large sellers charge tax in most states.
Each example below was run through the calculator on this page when the site was built, so the numbers match what you see when you enter the same inputs.
Total with 7.5% sales tax
$107.50
$100 of goods plus $7.50 of sales tax
Three layers of tax, one base: the state, county and city rates are each charged on $100, not on each other.
Total with 8.875% sales tax
$10,876.61
$9,990 of goods plus $886.61 of sales tax, for 10 items at $999.00 each
Quantity is applied before the tax, so the extended price is what gets taxed - exactly as a till rings it up.
Price with the tax taken out
$2,140.00
$2,000 of goods plus $140.00 of sales tax
The tax inside the total is $140, which is 7% of the pre-tax price but only 6.54% of what was handed over.
Divide the total by 1 plus the rate as a decimal. A $107.50 total at 7.5% is $107.50 / 1.075 = $100 of goods, so the tax is $7.50. Multiplying $107.50 by 7.5% would give $8.06 and overstate the tax.
Alaska, Delaware, Montana, New Hampshire and Oregon have no statewide sales tax. Alaska still allows local sales tax, and the other four have specific local taxes such as lodging or restaurant tax in some places.
Because the rate on the receipt is the combined rate: state plus county plus city plus any special district. Some states also add a statewide local rate instead of charging each city separately.
It depends on the state. Many states tax only tangible goods, others tax specific services such as repairs or landscaping, and a few tax nearly everything. If your invoice mixes goods and services, tax typically applies only to the taxable lines.
Usually yes. After the economic nexus rules that followed the 2018 South Dakota v. Wayfair decision, sellers above a state sales threshold collect that state tax even with no physical presence there.
No. Sales tax is added once at the final retail sale, while VAT is charged at each stage of production with businesses reclaiming the input tax. The arithmetic on a retail receipt looks identical, which is why the two get mixed up.
Last reviewed 2026-09-14. This page is an estimate tool, not financial, tax or legal advice.Read the full disclaimer.