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Sales Tax Add & Extract Calculator
Applies a user-entered sales tax rate to add tax to a pre-tax amount or extract tax from a tax-inclusive total. Does not look up jurisdiction rates.
Limitation: Educational arithmetic only.
How to Estimate Sales Tax on a Purchase
Keep one currency and one assumed rate for the scenario.
Choose a display currency (no FX conversion occurs).
Rates are not universal
City, county, and special-district components often stack. Confirm the rate that applies to your transaction before relying on any total.
What the Sales Tax Result Means
The worksheet returns pre-tax amount, tax, and total under your entered rate. It does not decide whether an item is taxable.
Worked Sales Tax Examples
Add 8.25% to $100
Inputs
Result
Tax is 8.25; total is 108.25.
Extract 8.25% from 108.25
Inputs
Result
Dividing by 1.0825 recovers the pre-tax price and 8.25 tax.
Zero rate
Inputs
Result
At 0%, tax is zero and totals match the entered amount.
Frequently Asked Questions
Still have questions about this calculation?
Try the CalculatorSales Tax Formulas
Transparent percent arithmetic with two-decimal currency rounding.
Formula
Add tax
tax = round(amount × rate ÷ 100); total = amount + tax
Extract tax
pre-tax = round(amount ÷ (1 + rate ÷ 100)); tax = amount − pre-tax
Scientific Background
Assumptions: a single combined rate and one currency. Limitations: destination vs origin sourcing, exemptions, caps, and marketplace facilitator rules are not modeled. Confirm with state or local authorities when filing or collecting tax.
Sources & review
Sales Tax Calculator documents the references behind its formulas and assumptions. Always treat results as educational estimates, not personalized professional advice.
Last reviewed
July 22, 2026
IRS digital assets / tax reference
Internal Revenue Service (IRS)
https://www.irs.gov/businesses/small-businesses-self-employed/sales-tax-deductionFree Calculator Hub methodology
Free Calculator Hub
/methodology
See our methodology and corrections policy.