Reverse Sales Tax / Backwards Sales Tax Calculator

When you buy something in many countries or states, the final price you pay already includes sales tax. But sometimes you need to know the original price before tax. This is where a Reverse Sales Tax Calculator (also called a Backwards Sales Tax Calculator) becomes useful.

Instead of adding tax to a price, this calculator removes the tax portion from the total price to find the original amount and the tax amount.

This tool is commonly used by:

• Businesses reviewing invoices
• Accountants calculating tax portions
• Online sellers determining base product prices
• Customers who want to know how much tax they paid

With just the total price (including tax) and the tax rate, you can easily calculate the price before tax and the tax amount.

Reverse Sales Tax Formula

To calculate the original price before tax, we divide the total price by 1 + tax rate.

Formula

$\text{Price Before Tax}=\frac{\text{Total Price}}{1+\frac{\text{Tax Rate}}{100}}$

Sales Tax Amount Formula

Once you know the original price, you can find the tax amount by subtracting the original price from the total price.

Formula

$\text{Sales Tax Amount}=\text{Total Price}-\text{Price Before Tax}$

Step-by-Step Reverse Sales Tax Calculation

To calculate the price before tax manually:

1. Take the total price including tax
2. Convert the tax rate percentage into decimal
3. Add 1 to the tax rate
4. Divide the total price by that value
5. Subtract the original price from the total price to get the tax amount

This method works for any tax rate, such as 5%, 7%, 8.25%, or 10%.

Example Calculation

Suppose:

• Total Price (including tax) = $108
• Sales Tax Rate = 8%

Step 1: Find Price Before Tax

$\text{Price Before Tax}=\frac{108}{1+\frac{8}{100}}$​​​​​​​

Step 2: Simplify

$\text{Price Before Tax}=\frac{108}{1.08}$

Step 3: Result

$\text{Price Before Tax}=100$

Step 4: Calculate Tax Amount

$\text{Sales Tax Amount}=108-100$

Final Result

• Price Before Tax = $100
• Sales Tax Amount = $8

Why Use a Reverse Sales Tax Calculator?

A reverse sales tax calculator saves time and prevents manual calculation errors. It is especially useful when:

• Receipts show only the final taxed price
• Businesses need to separate revenue and tax
• Accountants need accurate tax reporting
• Online sellers want to determine base product prices

Instead of doing manual calculations, you can simply enter:

• Total Price (Including Tax)
• Sales Tax Rate (%)

The calculator instantly returns:

• Original Price Before Tax
• Sales Tax Amount