Add sales tax or reverse it from a total
Sales tax is a percentage of the price before tax. To add it, multiply the price by the rate and add the result: 100.00 at 6.5% carries 6.50 of tax and costs 106.50 in total. To reverse it from a receipt total, divide by one plus the rate. This page does both, finds the rate when you know the before-tax and after-tax prices, and totals a basket in which only some items are taxable.
Use it at the till, on a quote or on an invoice: enter the combined rate that applies, choose what you know and press Calculate. The same page covers a single item and a whole basket, so you can check one price or a full receipt without switching tools.
Sales tax formulas and the tax base
Write the rate as a decimal t, so 6.5% is 0.065. The tax is price × t, the total is price × (1 + t), and the price before tax is the total ÷ (1 + t). The rate is always measured against the price before tax, which is called the tax base. That base is the number the rest of the maths depends on, so it matters which prices a store taxes and which it does not.
Three quantities are linked by the rate. Know any two of the price before tax, the rate and the price after tax and the third follows. The tax amount itself is the difference between the two prices. A rate of zero leaves the price unchanged, and a before-tax price of zero carries no tax at any rate.
Net denominator versus gross
The rate is tax divided by the price before tax, not by the total. A 110.00 receipt with 10% tax contains 10.00 of tax on a 100.00 price. Taking 10% off the total would remove 11.00 and leave 99.00, which is wrong because the 10% was charged on the smaller before-tax price. Dividing by 1.10 undoes the addition exactly.
Worked receipt: taxable and non-taxable items
Many receipts mix items. Suppose one item costs 100.00 and is taxable, and another costs 50.00 and is not, with a 10% rate on taxable items. Tax applies to the 100.00 only, so the tax is 10.00, the total before tax is 150.00 and the total after tax is 160.00. The effective rate on the whole basket is 6.67%, lower than 10% because part of the basket is untaxed.
The same basket entered the way a receipt shows it works too. If the taxable line reads 110.00 including tax and the other reads 50.00, the calculator takes the tax back out of the taxable line only and arrives at the same totals: 150.00 before tax, 10.00 of tax and 160.00 after tax. Which items are taxable is your input; the tool does not know the rules of any place and applies none of them.
Add a third item of 25.00 that is taxable and the picture changes: the taxable part becomes 125.00, tax at 10% is 12.50, and the basket totals 187.50 including the untaxed 50.00. Because the untaxed item is part of the total but not of the tax base, the effective rate on the whole basket is 7.14%. Reading a receipt line by line like this is the quickest way to see which items were taxed.
Find a rate from before-and-after prices
If you know both prices, the rate is the after-tax price divided by the before-tax price, minus one. A 100.00 item that costs 110.00 at the till has a rate of 10%. This needs a before-tax price above zero and an after-tax price at least as large; otherwise the rate is undefined and the calculator says so instead of guessing. The rate you find is the combined rate for that purchase. If it is not a round number, the receipt may include a taxable and a non-taxable item, a rounding effect or a separate charge.
A common use is checking a restaurant or hotel bill. If a 60.00 meal comes to 65.00, the rate is 8.33%, which does not look like a standard rate and suggests a service charge, a rounded line or an extra fee rather than a tax. Finding the rate from two prices is a good first test of whether a receipt adds up.
Why receipts can differ by a cent
A cent of difference is normal and usually comes from rounding. Take three taxable items of 0.05 at 10%. Each carries 0.005 of tax, which rounds half-up to 0.01, so rounding line by line gives 0.03 of tax. Adding the three unrounded amounts first gives 0.015, which rounds to 0.02. Both follow a clear rule and neither is a mistake. The calculator rounds each line by default, lets you round the taxable group once instead, and shows a rounding-adjustment row so the totals add up. A till may use its own method again, and a discount can change the amount that is taxed, so check the taxable flags and the discounted prices before you suspect an error.
Discounts add another source of differences: a store may tax the price before a coupon or after it, and that choice changes the amount that is taxed. Enter the amount the store actually taxed, not the sticker price, when you try to match a receipt.
Finding the applicable rate
This calculator does not look up rates and does not know your city, state or the item you are buying. Enter the combined rate that applies to your purchase, taking it from the receipt, the seller or the official guidance of the tax authority where you buy. If you only have a before-and-after pair of prices, the find-the-rate mode gives you the rate that was actually charged. A single combined rate is assumed; if several taxes with different bases apply, work them out separately.
Rates can differ by item category, by delivery address and by the date of the sale, so a rate that was right last year or for another purchase may not apply now. When in doubt, ask the seller or read the guidance published by the tax authority.
Sales tax compared with VAT and tips
Sales tax and value-added tax use similar arithmetic but are different systems with different invoices and terms, so there is a separate tool for each: add or remove VAT for tax-inclusive prices and invoices with several rates. A tip is not a tax and is usually calculated on a different base. On a 60.00 meal at 8.25% the tax is 4.95 and the total is 64.95; check the tax on a bill and split it before you decide how to tip. To compare prices fairly, compare unit prices after sales tax, and to see the margin a seller keeps, use the margin and markup calculator. If a discount applies before tax, add tax to your sale price after working out the discounted price.
Sales tax questions
How do I calculate sales tax?
Multiply the taxable price before tax by the rate divided by 100. At 6.5%, a 100 price carries 6.50 of tax. Add that to the price to get the total. Round to the cent after you multiply. For several items, tax each taxable line and add the results, or tax the taxable total once; the basket mode shows both. If you enter the rate as 6.5, the calculator treats it as 6.5%, not 650%.
How do I calculate the price before tax?
Divide the total by one plus the rate divided by 100. A total of 110 at 10% divides by 1.10 to give 100 before tax. Subtracting 10% of the total would give the wrong price. Check the answer by adding the tax back to the price before tax.
Can this find my local rate?
No. The calculator does arithmetic with the rate you enter and does not look up rates by place. Take the rate from a receipt, the seller or the official source for where you buy. The find-the-rate mode tells you the rate that was actually charged on a receipt, which you can then compare with the official figure.
Why does my receipt differ slightly?
Check which items are taxable, whether a discount changed the taxed amount and how the till rounds. A difference of one cent can come from rounding alone and is not necessarily a mistake. Compare the taxed amount first and the rounding second. Receipts that show tax on each line can differ from receipts that tax the whole total.
Are VAT and sales tax the same?
No. They are different tax systems that happen to share arithmetic. Use the dedicated VAT calculator for tax-inclusive prices and invoices that mix rates. The main differences are where in the supply chain the tax is charged and how it appears on invoices.