Sales Tax Calculator
This sales tax calculator works in three directions. Add tax to a pre-tax price, take the tax back out of a total you already paid, or find the tax rate from a price and a total. Each mode shows the tax amount, the totals, the formula with your numbers substituted and the steps, rounded to the cent the way a receipt is.
How to use the sales tax calculator
- Choose a mode. Add tax to a price is the default.
- Enter the numbers that mode asks for. The defaults are a price of
$50and a tax rate of8.25%. - Read the tax and the total at the top, with the formula and steps underneath. Change the currency symbol if you need to.
With the defaults, the tax is $50 × 0.0825 = $4.125, which rounds to $4.13, and the total is $54.13.
The other two modes start from that same receipt so you can see how they relate:
- Take tax out of a total: total
$54.13at 8.25% gives a pre-tax price of$50.00and tax of$4.13. - Find the tax rate: price
$50and total$54.13give a rate of8.26%.
That last answer is 8.26%, not 8.25%, and the difference is not an error. The section on rounding below explains why.
The rate you type is up to you. The calculator has no built-in list of state or city rates, because sales tax depends on the state, the county, the city and sometimes the type of item, and those rates change. Look up the combined rate for the place of purchase, then enter it here.
The sales tax formulas
Adding tax is a percentage of a number followed by an addition. Folding the two into one multiplier, 1 + rate, is faster and is the key to the other two modes. At 8.25% the multiplier is 1.0825, so every pre-tax dollar becomes $1.0825 at the register. For a quick estimate without a calculator, the guide to working out discounts, sales tax and tips in your head builds the tax from 1% and 10% pieces.
Taking tax out is the same multiplication run backwards, so it is a division. It is the same idea as the reverse percentage calculator, which works back to an original amount from any percentage increase.
Finding the rate is a percentage change from the price to the total. The base is always the pre-tax price, because that is what the rate was applied to.
Worked examples
Example: adding 6% tax to $1,299
A laptop is priced at $1,299 in a place where the combined rate is 6%.
Both routes give the same total. The multiplier route needs one step instead of two.
Example: taking 7% tax out of $32.10
A receipt shows only the total, $32.10, and you know the rate was 7%. You need the pre-tax price for an expense report.
Check it forward: $30.00 × 1.07 = $32.10. If you had subtracted 7% of $32.10 instead, you would get $29.85 and be wrong by 15 cents.
Example: finding the rate from a receipt
An item is priced at $34.00 and the receipt total is $36.38.
The rate came out exact here. On small amounts it often does not, which is the next section.
Why rounding to the cent changes the answer
Sales tax is almost never a whole number of cents. On the default $50 at 8.25%, the exact tax is $4.125, and a register rounds it to $4.13. Once that rounding happens, the receipt no longer holds enough information to recover the exact rate.
The rate mode reports $4.13 ÷ $50 = 8.26%, the middle of that range. If you know the official rate is 8.25%, trust that number; the 8.26% is what the rounded receipt implies, not a different rate. The larger the purchase, the narrower the range, so a rate worked out from a $500 receipt is far more precise than one from a $5 receipt.
The same effect explains small differences between a receipt and a hand calculation when several items are bought together. Taxing each item separately and adding the rounded amounts can give a different answer from taxing the subtotal once:
Four cents is a big gap on a small order. Receipts usually tax the subtotal, which is why a total that looks a cent or two different from your own working is normally a rounding question, not a pricing error. The rounding calculator shows exactly which way any value rounds.
Sales tax multipliers and divisors
These rates are round example figures to show the arithmetic, not current rates for any particular state or city. The middle columns are the numbers to multiply by when adding tax and to divide by when removing it.
| Rate | Multiply to add tax | Tax on $100 | $100 total, pre-tax | $100 total, tax inside |
|---|---|---|---|---|
| 5% | × 1.05 | $5.00 | $95.24 | $4.76 |
| 6% | × 1.06 | $6.00 | $94.34 | $5.66 |
| 7% | × 1.07 | $7.00 | $93.46 | $6.54 |
| 7.5% | × 1.075 | $7.50 | $93.02 | $6.98 |
| 8% | × 1.08 | $8.00 | $92.59 | $7.41 |
| 8.25% | × 1.0825 | $8.25 | $92.38 | $7.62 |
| 9% | × 1.09 | $9.00 | $91.74 | $8.26 |
| 10% | × 1.10 | $10.00 | $90.91 | $9.09 |
The last column is always smaller than the rate. At 10%, a $100 total contains only $9.09 of tax, because the 10% was applied to $90.91, not to $100. This asymmetry is the source of the most common sales tax mistake.
Combined state and local rates
In most places that charge sales tax, the rate on a receipt is a stack of several rates added together: a state rate, plus county, city or special-district rates on top. As a made-up illustration, a 6% state rate plus a 1.5% county rate plus a 0.75% city rate makes a combined rate of 8.25%, and that combined figure is what you enter. The pieces are added, not multiplied, because each one applies to the same pre-tax price. Rates and the items they cover vary by location and change over time, so check the state or local revenue department for the place of purchase.
Sales tax on discounted prices
When an item is on sale, tax is normally charged on the price you actually pay. For an $80 item at 25% off with 7% tax:
The order of the percentages does not matter to the math: $80 × 0.75 × 1.07 and $80 × 1.07 × 0.75 both give $64.20, because multiplication can be done in any order. What matters is that the discount and the tax are both multipliers on the price, not percentages to add or subtract from each other. Taking 25% off and adding 7% is not the same as taking 18% off. The percent off calculator handles the sale price and tax together, and the guide to multiplying percentages explains why stacked percentages behave this way.
Coupons, rebates and trade-ins can be treated differently from store discounts depending on the state, so the taxable amount on a receipt is not always the price after every deduction.
Common mistakes
- Removing tax by subtracting the rate. $54.13 minus 8.25% of $54.13 is $49.66, not $50. Divide by 1.0825 instead.
- Misplacing the decimal point. 8.25% is 0.0825, not 0.825. Using 0.825 gives tax ten times too large. The percent to decimal calculator shows the conversion.
- Finding the rate against the total. $4.13 ÷ $54.13 is about 7.63%, which is the tax share of the total, not the tax rate.
- Using only the state rate. Local rates are often added on top. Use the combined rate for the place of sale.
- Expecting the rate mode to match the official rate exactly. Rounding to the cent loses precision, especially on small amounts.
- Rounding the tax before using it again. Keep the exact tax for further steps and round once at the end, as the guide on rounding to decimal places explains.
Frequently asked questions
How do you calculate sales tax?
Convert the rate to a decimal and multiply it by the price. For $50 at 8.25%, $50 × 0.0825 = $4.125, which rounds to $4.13, so the total is $54.13. You can also multiply the price by 1 + rate to get the total in one step: $50 × 1.0825 ≈ $54.13.
How do you take sales tax out of a total?
Divide the total by one plus the rate as a decimal. For a $54.13 total at 8.25%, $54.13 ÷ 1.0825 ≈ $50.00, so the tax was $4.13. Do not subtract 8.25% of the total; that gives $49.66, because the tax was calculated on the pre-tax price, not on the total.
How do I find the sales tax rate from a receipt?
Subtract the price from the total to get the tax, then divide the tax by the price and multiply by 100. For a $34.00 item with a $36.38 total, the tax is $2.38 and the rate is $2.38 ÷ $34.00 × 100 = 7%. Small receipts give less precise rates because the tax was rounded to the cent.
What is 7% sales tax on $100?
Seven percent sales tax on $100 is $7.00, making the total $107.00. On $100 the tax in dollars always equals the rate, which makes it a handy check. Going the other way, a $100 total at 7% contains about $6.54 of tax on a pre-tax price of about $93.46.
Why does the calculator say 8.26% when the rate is 8.25%?
Because the receipt was rounded. At 8.25%, the tax on $50 is $4.125, shown as $4.13. Working backwards from $4.13 gives 8.26%. Any rate from 8.25% up to just under 8.27% produces the same rounded tax, so the receipt cannot tell them apart. If you know the official rate, use it.
Is sales tax calculated before or after a discount?
Store discounts are normally taken off first, and tax is charged on the lower price. An $80 item at 25% off with 7% tax costs $60 plus $4.20 tax, $64.20 in total. Mathematically the order does not change the result, since both are multipliers, but some coupons and rebates are treated differently depending on the state.
How do combined sales tax rates work?
The state rate and any county, city or district rates are added together into one combined rate, which is then applied to the price. As an illustration, rates of 6%, 1.5% and 0.75% combine to 8.25%. Rates differ by location and change over time, so check the local revenue department for the current combined rate.
Related calculators
Guides that use this calculator
Longer explanations of the method behind it, with worked examples.
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