Reverse Sales Tax Calculator
Back-calculate the pre-tax price from a total amount and sales tax rate.
Calculate Sales Tax
Results
Original Amount (Excluding Tax)
$0.00
Sales Tax Amount
$0.00
Data Source and Methodology
All calculations are based on standard sales tax formulas. Ensure that you use the correct tax rates for accurate results.
The Formula Explained
Original Amount: Original = Total / (1 + Tax Rate / 100)
Sales Tax: Tax = Total - Original
Glossary of Terms
- Total Amount: The price paid including sales tax.
- Tax Rate (%): The percentage of sales tax applied.
- Original Amount: The price before sales tax.
- Sales Tax: The amount of tax included in the total price.
FAQs
What is sales tax?
Sales tax is a consumption tax imposed by the government on the sale of goods and services.
How do I find the correct sales tax rate?
Sales tax rates vary by location and type of goods or services. Consult local tax authorities for precise rates.
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
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Formula (extracted LaTeX)
\[{originalAmount.toFixed(2)}`; document.getElementById('salesTaxValue').textContent = `\]
{originalAmount.toFixed(2)}`; document.getElementById('salesTaxValue').textContent = `
Formula (extracted text)
Original Amount: Original = Total / (1 + Tax Rate / 100) Sales Tax: Tax = Total - Original
Variables and units
- T = property tax (annual or monthly depending on input) (currency)
Sources (authoritative):
- IRS — Forms, instructions, and publications — irs.gov · Accessed 2026-01-19
https://www.irs.gov/forms-instructions - IRS — Tax topics — irs.gov · Accessed 2026-01-19
https://www.irs.gov/taxtopics - IRS — Retirement plans — irs.gov · Accessed 2026-01-19
https://www.irs.gov/retirement-plans
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
- Initial audit spec draft generated from HTML extraction (review required).
- Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
- Confirm sources are authoritative and relevant to the calculator methodology.