How to Add or Reverse Sales Tax
To add tax, multiply the pre-tax price by the tax rate and add the result to the price. For example, $100 at 8.25% produces $8.25 of tax and a $108.25 total.
To reverse a tax-inclusive total, do not simply subtract 8.25% from the total. Divide the total by 1.0825 to recover the pre-tax price, then subtract that amount from the total to find the tax.
Why This Calculator Does Not Auto-Pick a State Rate
A state-level rate alone may not be the rate that applies to a purchase. Local jurisdictions can affect the combined rate, and sourcing rules determine which location's rate applies. Streamlined Sales Tax rate-and-boundary systems use address or ZIP-based jurisdiction information and are updated as rates and boundaries change.
Taxability also depends on what is being sold. A rate that applies to one taxable product does not establish that another product or service is taxable in the same way. For an actual transaction, verify the rate and taxability with the relevant tax authority or an official rate lookup.
Economic Nexus Is Not One National Threshold
Remote-seller collection obligations are separate from the arithmetic on this page. There is no single nationwide “$100,000 or 200 transactions” rule. Threshold amounts, transaction-count tests, measurement periods, included sales and registration timing vary by state, and states continue to change those rules.
For example, current state-by-state guidance shows $500,000 sales thresholds in California and Texas, while a number of states have removed transaction-count thresholds. Physical presence can also create nexus independently of an economic threshold.
Sales Tax Calculator FAQ
How do I calculate sales tax on a purchase?
Multiply the taxable pre-tax price by the applicable combined sales-tax rate. Add the resulting tax to the pre-tax price for the total.
How do I remove sales tax from a total?
Divide the tax-inclusive total by 1 plus the tax rate expressed as a decimal. The difference between the total and that pre-tax amount is the included tax.
Why can the sales-tax rate differ within the same state?
Local taxing jurisdictions can add rate components to a state rate. The applicable jurisdiction can also depend on sourcing rules, which is why a transaction-specific combined rate is more useful than a state rate alone.
Do Delaware, Montana, New Hampshire and Oregon have statewide sales tax?
Current economic-nexus references list these states as having no general state sales tax. Alaska has no statewide sales tax but participating local municipalities can impose local sales taxes, so location still matters.
Does crossing $100,000 in sales always create economic nexus?
No. Economic-nexus thresholds and measurement rules vary by state. Some use $100,000, others use different dollar thresholds, and transaction-count tests have been removed in several states. Check the current rule for the specific state.
Rate and compliance references: Streamlined Sales Tax rate and boundary updates, Streamlined Sales Tax taxability matrices, and Sales Tax Institute state-by-state economic nexus guide.