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Sales Tax Calculator

Quickly add sales tax to a price or extract the original price from a tax-inclusive total.
Calculator
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Analysis
Interpretation of the current calculator output

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How to Use

Step-by-step instructions
  1. 1Select whether you are ADDING tax to a price, or EXTRACTING tax from a total.
  2. 2Enter the dollar amount.
  3. 3Enter the local sales tax percentage rate.
  4. 4View exactly how much of the total transaction was tax.

Sales Tax Arithmetic

Adding tax is simple multiplication. Extracting tax from a total (finding the pre-tax price) requires division, because the tax is based on the original smaller number, not the final total.
Gross = Net × (1 + Tax Rate) // Net = Gross ÷ (1 + Tax Rate)

Variables:

GrossTotal out-the-door price including tax
NetBase item price before tax
Tax RatePercentage tax expressed as a decimal (e.g., 8% = 0.08)

Example

Extracting Tax from a $100 Receipt

Inputs:

Mode:Extract Tax
Amount:$100
Tax Rate:8.5%

Steps:

  1. 1.Convert percent to decimal: 8.5% = 0.085
  2. 2.Apply extraction formula: Base = Gross / (1 + Rate)
  3. 3.Calculate: Base = 100 / 1.085
  4. 4.Base = $92.17. Tax is the difference.
Result:
$92.17 Base Price + $7.83 Tax = $100.00 Total

Frequently Asked Questions

Why can't I just multiply the total by the tax rate to find the tax?

Because the tax rate was applied to the ORIGINAL smaller price, not the total. For example, a $100 item + 10% tax = $110. If you try to extract tax by doing $110 * 10%, you get $11, which is incorrect (the tax was $10).