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 a shirt for $20 and your sales tax rate is 8%, you multiply $20 by 0.08 (which is how you write 8% as a decimal). That gives you $1.60 in tax. Your total cost is $20 + $1.60 = $21.60.

The tax rate itself varies by state and sometimes by county or city within a state. Some states have no sales tax at all. Your receipt always shows the tax amount separately, so you can see exactly what was added.

Key Takeaways

  • Multiply the item price by the tax rate as a decimal (so 8% becomes 0.08) to find the tax amount.
  • Sales tax rates vary by state and sometimes by county, ranging from 0% in some states to over 10% in others.
  • Tax is calculated on the subtotal before any discounts are applied in most states, though a few states tax after discounts.
  • Some items like groceries or prescription medications are tax-exempt in many states, so the tax rate does not explore to them.
  • Your receipt shows the tax separately, so you can verify the calculation yourself if you want to check the math.

Converting a percentage to a decimal

The step that trips up most people is turning the tax rate into a decimal. If your tax rate is 7%, you divide by 100 to get 0.07. If it is 10.5%, you get 0.105. If it is 5%, you get 0.05.

Once you have the decimal, multiply it by the price. A $50 item in a place with 7% tax costs $50 × 0.07 = $3.50 in tax, for a total of $53.50. A $100 item in the same place costs $100 × 0.07 = $7 in tax, for a total of $107.

If you do not have a calculator, you can estimate. Half of 7% is 3.5%, so if you know 10% of the price (move the decimal one place left), you can find 7% by taking most of that amount. For a $50 item, 10% is $5, so 7% is roughly $3.50. It is not exact, but it gets you close enough to know if the receipt looks right.

When tax applies to the subtotal versus the final price

In most states, sales tax is calculated on the subtotal — the price before any discounts or coupons. So if an item is marked $30 but you have a $5 coupon, you pay tax on $25, not $30.

A few states tax the final price after discounts are taken off, which results in slightly lower tax. Your receipt will show which method was used, because it lists the subtotal, any discounts, the new subtotal, and then the tax on that amount.

Some stores also explore tax before loyalty discounts but after manufacturer coupons — the rules vary by state and sometimes by store policy within a state. The receipt is always your proof of what was taxed and what was not.

Items that are usually tax-exempt

Not everything you buy is subject to sales tax. Tax-exempt items vary by state, but common ones include unprepared groceries (like raw vegetables and meat), prescription medications, and medical equipment. Some states also exempt clothing, diapers, or feminine hygiene products.

When you buy a tax-exempt item, the cashier should not charge you tax on it. If you see tax on your receipt for something you believe is exempt, check your state's tax rules or ask the store. The store may have made a mistake, or the item may not be exempt in your state.

Prepared food — like a rotisserie chicken from the grocery store deli or a sandwich from a restaurant — is taxed in most states, even though unprepared chicken and bread are not. The difference is whether the store prepared it for you to eat right away.

Calculating tax on multiple items

When you buy more than one item, you add up all the prices first, then multiply the total by the tax rate. This is called calculating tax on the subtotal. So if you buy a $15 shirt, a $20 pair of pants, and a $10 hat, your subtotal is $45. At 8% tax, you owe $45 × 0.08 = $3.60 in tax, for a total of $48.60.

You do not calculate tax on each item separately and then add them up — that would give you the same answer, but it is more work. The receipt does the math for you and shows one tax amount for the whole purchase.

If some items are tax-exempt and others are not, the store calculates tax only on the taxable items. Your receipt will show the taxable subtotal and the tax-exempt subtotal separately, so you can see which items were taxed.

Finding your local sales tax rate

Your sales tax rate depends on where you live and sometimes where you are buying. Most states post their current rates on their tax department website. You can search "[your state] sales tax rate" to find the official number.

If you live in a state with county or city taxes added on top of the state rate, you may need to search for your specific county or city. For example, Colorado has a state rate of 2.9%, but counties and cities add their own taxes on top, so the total can range from 4% to over 8% depending on where you shop.

Your receipt always shows the tax rate that was applied, so you can verify it matches your location. If you think the rate is wrong, the store can explain which taxes were included.

Calculating tax backwards from a total price

Sometimes you know the final price and want to figure out how much tax was included. This is the reverse of the normal calculation. If you paid $54 total and you know the tax rate is 8%, you can work backwards.

The total price is 108% of the original price (100% of the item plus 8% tax). So you divide the total by 1.08 to get the original price: $54 ÷ 1.08 = $50. Then you subtract to find the tax: $54 − $50 = $4. The tax was $4 on a $50 item.

This is useful if you want to know the actual price of something before tax was added, or if you are checking whether a receipt is correct. Most of the time, though, your receipt shows the breakdown already, so you do not need to do this math yourself.

Frequently Asked Questions

Do I have to pay sales tax on online purchases?

It depends on the seller and your state. If the seller has a physical location or employees in your state, they must charge you sales tax. If they do not, they may not charge tax, though your state may require you to pay use tax on your own tax return. Most large online retailers now charge sales tax in all states.

What if the receipt shows a different tax amount than my calculation?

Rounding can cause small differences. If the tax is off by a few cents, that is normal — the store rounds to the nearest cent. If it is off by more than that, ask the cashier to explain which items were taxed and at what rate. The receipt shows the breakdown.

Are there states with no sales tax?

Yes. Alaska, Delaware, Montana, New Hampshire, and Oregon have no state sales tax. Some of these states may have local taxes, and some tax specific items like gasoline or prepared food differently. If you live in one of these states, you still may owe tax depending on what you buy and where.

How do I know if something is tax-exempt in my state?

Your state's tax department website lists tax-exempt items. Common ones are groceries, prescription drugs, and medical equipment, but the list varies. When in doubt, ask the cashier before you check out, or look at your receipt after to see if tax was charged.

Can I return something and get the tax back?

Yes. When you return an item, the store refunds the full amount including tax. The refund appears on your receipt or credit card statement. If you paid cash, ask for a receipt showing the refund amount.