To calculate the price before sales tax, divide the tax-inclusive total by one plus the tax rate written as a decimal. For example, when a total of $108 includes tax at 8 percent, divide $108 by 1.08 to recover the original pre-tax price of $100.
Add tax to a price or extract included tax using the percentage rate you provide.
The inclusive total contains both the original price and tax calculated from that smaller original amount.
Formula for the Price Before Sales Tax
A tax-inclusive price is made up of the original price plus a percentage of that original price.
Convert the tax rate to decimal form, add one, and divide the inclusive total by the resulting multiplier.
The Sales Tax Calculator can perform this calculation using its Tax included mode.
How to Calculate the Pre-Tax Price Step by Step
Begin with the final price and the tax rate included in that amount.
- 1Convert the percentage to a decimal
Divide the percentage rate by 100. An 8 percent rate becomes 0.08.
- 2Create the tax multiplier
Add one to the decimal rate. One plus 0.08 equals 1.08.
- 3Divide the inclusive total
Divide the final price by the multiplier to recover the amount before tax.
Worked Example: $108 Including 8% Tax
Convert 8 percent to 0.08 and add one to create a multiplier of 1.08.
Divide the inclusive total of $108 by 1.08.
The original price before tax is $100. The included tax is $8.
Why You Cannot Simply Subtract 8%
Subtracting 8 percent of $108 removes $8.64 and leaves $99.36.
That is incorrect because the original tax was not calculated from $108.
The tax was 8 percent of the smaller pre-tax price of $100.
How to Find the Included Tax
After finding the pre-tax price, subtract it from the tax-inclusive total.
For a $108 total with a $100 pre-tax price, the included tax is $8.
This method avoids applying the percentage rate to the wrong base.
Example with a 7.5% Tax Rate
Suppose a final price of $215 includes tax at 7.5 percent.
The multiplier is 1.075.
Dividing $215 by 1.075 gives a pre-tax amount of $200 and included tax of $15.
Example with a Decimal Price
Suppose a total of $53.87 includes tax at 6 percent.
Divide $53.87 by 1.06 to estimate the original price.
Round the recovered amount and included tax according to the currency and receipt method used.
Pre-Tax Price for Multiple Items
When the entered total covers several identical items, recover the combined pre-tax subtotal first.
Divide that subtotal by the quantity to estimate the pre-tax price per item.
Small differences may occur when the original checkout rounded tax separately for each item.
Pre-Tax Price after a Discount
A final total may reflect both a discount and tax.
You must know whether the entered inclusive amount is before or after the discount and which amount was taxable.
When the final amount after discount includes tax, remove the included tax first and then analyse the discount separately.
Tax-Inclusive Pricing and Rounding
Displayed tax-inclusive prices are often rounded to the smallest currency unit.
The recovered pre-tax amount may therefore contain more decimal places than the displayed price.
Use the rounding method shown on the original invoice when an exact accounting result is required.
Common Mistakes
Do not subtract the tax percentage directly from the inclusive amount.
Do not divide by the decimal rate alone; divide by one plus the decimal rate.
Do not assume that every part of a final bill received the same tax treatment.
Conclusion
Divide the tax-inclusive total by one plus the decimal tax rate to find the price before sales tax.
Subtract the recovered pre-tax price from the final amount to find the included tax.
Use Tax included mode in the Sales Tax Calculator to complete both calculations.
FAQs
How do I calculate the original price before tax?
Divide the tax-inclusive total by one plus the decimal tax rate.
What is the pre-tax price of $108 with 8 percent tax?
The pre-tax price is $100 and the included tax is $8.
Why can I not subtract 8 percent from $108?
Because the 8 percent tax was calculated from the smaller pre-tax price.
How do I find the included tax?
Subtract the recovered pre-tax price from the inclusive total.
Can rounding affect the result?
Yes. Tax-inclusive totals and line-item taxes may have been rounded.
These examples explain percentage calculations only. Tax rates, exemptions, taxable amounts, pricing requirements, discount treatment, and rounding rules vary. Confirm the current requirements that apply to the transaction.