Reverse Sales Tax Calculator – Easily Calculate Sales Tax Backwards

This reverse sales tax calculator is particularly valuable when you only know the final price (tax-inclusive amount) and need to work backwards to find the base price.

When you’re analyzing a receipt that shows a total amount of $108.25, and you know the local sales tax rate is 8.25%. The reverse sales tax calculator would help you determine that the original price before tax was $100.

Reverse Sales Tax Calculator

Final Price	Tax Rate	Calculation	Original Price	Tax Amount
$250.00	6%	$250.00 ÷ 1.06	$235.85	$14.15
$175.50	8.25%	$175.50 ÷ 1.0825	$162.13	$13.37
$89.99	5.5%	$89.99 ÷ 1.055	$85.30	$4.69
$1,299.99	9%	$1,299.99 ÷ 1.09	$1,192.65	$107.34
$45.75	4.75%	$45.75 ÷ 1.0475	$43.67	$2.08

Reverse Sales Tax Calculation Formula

The formula for backward calculating sales tax involves working with percentages and division.

Original Price = Final Price ÷ (1 + Tax Rate as decimal)

To convert this into a practical application:

• Convert the tax rate percentage to decimal form (divide by 100)
• Add 1 to the decimal tax rate
• Divide the final price by this number

• Final Price: $217.50
• Sales Tax Rate: 5%
• Calculation:
  • Convert 5% to 0.05
  • Add 1: 1.05
  • $217.50 ÷ 1.05 = $207.14 (original price)

How to Calculate Reverse Sales Tax?

Let’s walk through a detailed:

Step 1: Gather Required Information: Final price (tax-inclusive amount), Applicable tax rate for your jurisdiction

Step 2: Convert the Tax Rate: Convert the percentage to decimal form: Example: 7.5% becomes 0.075

Step 3: Create the Divisor: Add 1 to your decimal tax rate: 1 + 0.075 = 1.075

Step 4: Perform the Division: Divide the final price by your result from Step 3:

• If final price is $139.10
• $139.10 ÷ 1.075 = $129.40 (original price)

Step 5: Verify Your Calculation: To double-check your work:

• Multiply original price by tax rate: $129.40 × 0.075 = $9.70 (tax amount)
• Add tax to original price: $129.40 + $9.70 = $139.10 (matches final price)