The basic formula for sales tax

Sales tax is calculated by multiplying the price of an item by the tax rate for your location. The formula is: Item Price × Tax Rate = Sales Tax Amount. Then you add that tax to the original price to get your total cost.

For example, if you buy something for $100 and your sales tax rate is 8%, you multiply $100 by 0.08 to get $8 in tax. Your total cost is $108. The tax rate varies by state and sometimes by county or city, so the same item costs different amounts depending on where you buy it.

Key Takeaways

  • Multiply the item price by the tax rate (expressed as a decimal) to find the tax amount, then add it to the original price.
  • Sales tax rates range from 0% to over 10% depending on your state, and some states have no sales tax at all.
  • Some items are tax-exempt in most states, including groceries, prescription medications, and medical equipment, though rules vary by location.
  • When you see a price tag in a store, it usually does not include sales tax, so your checkout total will be higher.
  • Online purchases are increasingly subject to sales tax based on where you live, not where the seller is located.

Converting the tax rate to a decimal

Tax rates are usually shown as a percentage, but to do the math you need to convert that percentage to a decimal. Divide the percentage by 100, or move the decimal point two places to the left.

A 7% tax rate becomes 0.07. A 9.5% tax rate becomes 0.095. A 10% tax rate becomes 0.10. Once you have the decimal, multiply it by the price of the item. This works the same way whether you are calculating tax on a single item or a cart full of items.

Calculating tax on multiple items

When you are buying more than one thing, you can add up all the prices first, then multiply by the tax rate. This gives you the total tax on your entire purchase. For example, if you buy three items for $20, $15, and $30, your subtotal is $65. At an 8% tax rate, you multiply $65 by 0.08 to get $5.20 in tax, making your total $70.20.

Alternatively, you can calculate the tax on each item separately and then add those tax amounts together. Both methods give you the same answer. Most stores use the first method (tax the subtotal) because it is faster and avoids rounding errors.

Tax-exempt items and categories

Some purchases are not subject to sales tax in most states. Groceries — unprepared food you cook at home — are typically tax-free. Prescription medications are almost always tax-exempt. Medical equipment like wheelchairs, hearing aids, and diabetic supplies are often exempt, though the rules vary.

Items that are usually taxed include prepared food (restaurant meals, deli items, hot coffee), clothing in some states, and most non-food goods. The specific rules depend on your state and sometimes your county. If you are unsure whether something is taxable, ask the cashier or check your state's tax authority website.

Finding your local sales tax rate

Your state's sales tax rate is set by law and is the same everywhere in that state, but many cities and counties add their own local tax on top. Your total rate is the state rate plus any local additions. For instance, Colorado has a 2.9% state rate, but Denver adds 3.62%, making the total 6.52% in that city.

To find your exact rate, search "[your state] sales tax rate" or "[your city] sales tax rate" online. Your state's Department of Revenue or Tax Commission website lists the rates by location. You can also ask a cashier or look at a recent receipt to see what rate was charged in your area.

Why the price tag does not include tax

In the United States, stores display prices before tax is added. This is different from many other countries, where the price you see includes all taxes. The reason is that sales tax rates vary by location, and a store may have customers from different cities or counties with different tax rates. Showing the pre-tax price keeps the tag the same for everyone.

When you check out, the cashier or register adds the tax based on your location. This is why your receipt shows the subtotal, the tax amount, and the final total separately. Online retailers increasingly show the tax at checkout based on your address, so you see the full amount you will pay before you complete the purchase.

Calculating backwards from a total price

Sometimes you know the final total and want to figure out how much tax was included. This is the reverse of the normal calculation. If you know the total and the tax rate, divide the total by (1 + the tax rate as a decimal). For example, if your total is $108 and the tax rate is 8% (0.08), divide $108 by 1.08 to get $100. That was your original price, and the tax was $8.

This is useful if you are tracking expenses or trying to understand a receipt. You can also subtract the subtotal from the total to find the tax amount directly, which is often simpler if the receipt shows both numbers.

Frequently Asked Questions

Do I have to pay sales tax on online purchases?

Most online purchases are now subject to sales tax based on where you live, not where the seller is located. This applies to orders from large retailers and many smaller sellers. Some very small sellers may not collect tax, but you may still owe it to your state. Check your state's tax authority for the current rules.

What states have no sales tax?

Five states have no sales tax: Alaska, Delaware, Montana, New Hampshire, and Oregon. However, some of these states have other taxes (like Alaska's local taxes or New Hampshire's tax on prepared food). If you live in one of these states, you do not calculate sales tax on most purchases.

Can I get sales tax refunded if I overpaid?

No, sales tax is not refunded. If you believe you were charged incorrectly, check your receipt against your state's tax rate. If there is an error, contact the store. Tourists visiting from other states cannot reclaim sales tax they paid, though some countries offer refunds to international visitors — this does not apply in the U.S.

How do I calculate tax on a discount?

Apply the discount first, then calculate tax on the reduced price. If an item costs $100 and is 20% off, the new price is $80. Then multiply $80 by your tax rate. This is how stores do it — you pay tax on what you actually pay, not the original price.

Is there a difference between sales tax and use tax?

Sales tax is charged when you buy something. Use tax is a tax on items you buy out of state and bring home without paying tax. Most people do not pay use tax because it is rarely enforced for individual purchases. It mainly applies to businesses buying inventory out of state.