How it works
Enter the applicable combined state and local rate for the purchase. If your amount already includes tax, the calculator divides by one plus the rate to recover the pretax base. It does not identify the tax jurisdiction or taxable items.
Worked example
Show example inputs and result
Amount: 100 · Combined sales tax rate: 8.25 · Amount entered: Before sales tax.
- Total including sales tax
- $108.25
- Amount before tax
- $100.00
- Tax amount
- $8.25
Questions and answers
Does the calculator look up a ZIP code tax rate?
No. Rates and exemptions depend on location, product and transaction. Supply the applicable rate yourself; the example rate is not a nationwide rate.
Why are some results rounded?
Results display up to 8 decimal places. Calculations use the unrounded values; very small values use scientific notation. JavaScript floating-point arithmetic can introduce tiny rounding differences.
Are my inputs sent to a server?
The calculator processes inputs in your browser. Its code does not send your values to a server.
Method reviewed: October 8, 2026 · Methods & accuracy