✦ SOLVORY FREE TOOLS · BUSINESS & ECOMMERCE
Reverse Sales Tax Calculator — Free Online Tool
Remove an included flat percentage tax from a tax-inclusive purchase, receipt or invoice.
JavaScript is needed for the interactive tool. The formula and worked example remain available below.
How to use the Reverse Sales Tax Calculator
Remove an included flat percentage tax from a tax-inclusive purchase, receipt or invoice.
- Enter real measurements or prices in the interactive tool.
- Check unit labels and customize any applicable fees, waste allowances or product-specific rates.
- Review the result, formulas and limitations before using it in purchasing, pricing or production decisions.
Reverse Sales Tax Calculator: formula & methodology
Pre-tax price = total including tax ÷ (1 + tax rate as decimal); included tax = total − pre-tax price.
The tool uses your entered values and explicitly labeled assumptions. Final results may be rounded for display, while intermediate arithmetic retains available numeric precision. Verify material, tax, device or platform specifications relevant to your situation.
Worked example
If a receipt totals $108.25 including 8.25% sales tax, its before-tax value is $100 and included tax is $8.25.
Try the example above and then change values to reflect your own project or comparison.
Frequently asked questions
Can this handle multiple local taxes?
Only if they form one equivalent flat percentage of the same taxable base. Compound taxes and exemptions require separate calculations.
Why divide rather than subtract the tax rate?
The tax-inclusive amount equals 100% of the base plus the rate. Divide by one plus the decimal rate.
What if my receipt has exempt items?
Separate exempt and taxable lines first. A single flat percentage on the entire receipt cannot accurately reverse a mixed-tax bill.