The Basic Formula: Price × Tax Rate = Sales Tax

Sales tax is calculated by multiplying the item's price by the tax rate for your location. If an item costs $100 and your sales tax rate is 8%, you multiply $100 by 0.08 to get $8 in sales tax. The total you pay is $100 + $8 = $108.

The tax rate varies by state and sometimes by county or city within that state. Some states have no sales tax at all. Others charge between 4% and 10% depending on where you live. When you shop online or in person, the cashier or checkout system usually adds the tax automatically — but knowing how to calculate it yourself helps you understand what you're paying.

The price before tax is called the pre-tax price or subtotal. The tax rate is usually shown as a percentage. To convert a percentage to a decimal, divide by 100: 8% becomes 0.08, 6.5% becomes 0.065, and so on.

Key Takeaways

  • Multiply the item price by the tax rate as a decimal to find the tax amount, then add that to the original price.
  • Sales tax rates vary by state, county, and sometimes city, so the same item costs different amounts in different locations.
  • Some items are taxed at a lower rate or not taxed at all, depending on state law — groceries and prescription drugs are often exempt.
  • When you see a price tag in a store, that price usually does not include sales tax, so your final bill will be higher.
  • Online purchases may or may not include sales tax depending on the seller's location and your state's rules.

Working Backwards: Finding the Pre-Tax Price

Sometimes you know the total amount you paid and want to figure out how much was tax. This requires a different calculation. If you paid $108 total and the tax rate is 8%, you cannot simply subtract 8% from $108 — that gives you the wrong answer because the tax was calculated on the original price, not the total.

Instead, divide the total by 1 plus the tax rate as a decimal. For an 8% tax rate, divide by 1.08. So $108 ÷ 1.08 = $100. That $100 is the pre-tax price, and the remaining $8 is the tax.

This matters when you're budgeting or comparing prices. If a store advertises a $50 item and you want to know what it actually costs you, you need to add the tax for your location. If a receipt shows $54.50 and you want to know the pre-tax price, you work backwards using the tax rate.

When Sales Tax Does Not Apply

Not every purchase is taxed. Most states exempt certain categories of goods, most commonly groceries and prescription medications. Some states also exempt clothing, medical equipment, or items for business use. The exemptions vary significantly from state to state.

A grocery store receipt often shows some items with tax and some without. Fresh produce, meat, and dairy are usually not taxed. Prepared foods, candy, and soft drinks often are taxed because they are considered non-essential. If you're unsure whether something is taxed in your state, check your state's department of revenue website or ask the cashier.

Resale certificates are documents that businesses use to buy goods without paying sales tax if they plan to resell those goods. Individual shoppers do not use these. If you're buying something for personal use, you pay the tax that applies in your location.

Sales Tax on Multiple Items

When you buy several items, calculate the tax on the total subtotal, not on each item separately. Add up all the pre-tax prices first, then multiply that sum by the tax rate. If you buy a $20 shirt, a $15 pair of pants, and a $10 hat, your subtotal is $45. At 8% tax, you owe $3.60 in tax, for a total of $48.60.

This matters because some items in your cart may be taxed and others may not be. The cashier or checkout system handles this automatically by adding tax only to the taxable items. Your receipt will show the subtotal, the tax amount, and the final total. If you want to verify the calculation, add up only the taxable items and multiply by the rate.

Sales Tax Rates by State

State sales tax rates range from 0% to 7.25% at the state level. However, many counties and cities add their own local sales tax on top of the state rate. This means the total rate you pay can be 8%, 9%, 10%, or higher depending on where you are.

For example, California's state rate is 7.25%, but Los Angeles County adds 2.25%, bringing the total to 9.5% in some areas. Tennessee has a state rate of 9.55% before local additions. Some states like Oregon, Montana, New Hampshire, and Delaware have no state sales tax at all, though some of these states may have local taxes.

The rate that applies to your purchase is the one for the location where you make the purchase. If you buy something in a store, you pay the rate for that store's location. If you order online, the rules are more complex and depend on where the seller is located and your state's laws.

Online Purchases and Sales Tax

Online sales tax rules have changed in recent years. Large online retailers now collect and pay sales tax in most states, even if the company is not physically located there. This means you typically pay the sales tax rate for your location when you order online, just as you would in a store.

Smaller sellers and marketplaces may not collect sales tax. If tax was not charged at checkout, you may owe it when you file your state income tax return — though most individual shoppers do not track this. The safest approach is to assume you will owe sales tax on online purchases and budget accordingly.

Frequently Asked Questions

Do I pay sales tax on used items?

In most states, yes — used items are taxed the same way as new ones. The tax is based on the sale price, not the original price. Some states exempt used items sold by individuals, but sales at used goods stores or online marketplaces are typically taxed.

What if the price tag does not match what I was charged?

Check your receipt against the price tag. If the pre-tax price is wrong, ask the cashier to correct it. If the tax rate seems too high, verify the rate for your location on your state's revenue website. Mistakes happen, and stores will fix them if you point them out.

Can I return something and get the tax back?

When you return an item, the store refunds the full amount you paid, including tax. You do not get a separate refund for the tax — it is included in the total refund. If you paid $108 for something and return it, you get $108 back.

How do I know the tax rate for my city?

Search "[your state] sales tax rate" plus your city or county name. Your state's department of revenue website lists rates by location. You can also ask a cashier or check your receipt from a recent purchase — the receipt usually shows the tax rate applied.

Is sales tax the same everywhere in my state?

No. Most states have different rates in different counties and cities. Even neighboring towns can have different total rates because of local additions. Always check the rate for the specific location where you are shopping.