What is a Sales Tax Calculator?
A sales tax calculator does two jobs: it adds tax to a pre-tax price so you can see the checkout total, and it reverses a tax-inclusive receipt to reveal the pre-tax amount. In the US, tax rates vary by state, county, and city — often stacking up to a combined rate — so a quick calculator saves guessing at the register.
The Formula
To add tax to a price:
Total = Price × (1 + Tax% / 100)
To extract tax from a tax-inclusive total (reverse calculation):
Pre-tax = Total ÷ (1 + Tax% / 100)
Where Price is the ticket amount before tax and Tax% is your combined state + local rate.
Worked Example: $100 item at 8.25%
A $100 sweater in a California city with a combined 8.25% rate: Total = 100 × 1.0825 = $108.25. Sales tax portion = $8.25. Now flip it around — you have a $108.25 receipt and you need to back out the tax for an expense report: Pre-tax = 108.25 ÷ 1.0825 = $100.00, and tax = 108.25 − 100.00 = $8.25. Reverse calculations are a lifesaver at the end of the quarter.
Approximate US State Sales Tax Rates
(State-level only; cities and counties add 1–4% on top in most jurisdictions.)
- 0% (no state sales tax): Alaska, Delaware, Montana, New Hampshire, Oregon
- ~4%: Hawaii, Wyoming, Colorado (state portion)
- ~6%: Florida, Pennsylvania, Michigan, Maryland
- ~7%: Indiana, Mississippi, Rhode Island, Tennessee
- 7.25%: California (highest state base rate)
- Combined 9–10%+ with city/county: parts of California, Tennessee, Louisiana, Arkansas, Washington
When to Use This Calculator
- Retail checkout: preview a total before you get to the register.
- Expense reports: split a tax-inclusive receipt into pre-tax and tax lines.
- Contractor invoicing: add the correct rate to jobs across multiple jurisdictions.
- Deductible business tax: extract the sales tax portion for accounting or Schedule C.
- Cross-border shopping: compare a purchase in a no-tax state (Oregon, NH) to your home state.
Mistakes to Avoid
- Forgetting local add-ons: the state rate is only part of the story. A "6%" Florida rate is really 7–7.5% in most counties.
- Assuming groceries are taxed: most US states exempt unprepared groceries and prescriptions; prepared food (restaurants, deli) is almost always taxed.
- Missing compound-rate jurisdictions: in a few places, city rates apply on top of state-inclusive totals rather than the base price — rare but non-trivial for high-ticket items.
Frequently Asked Questions
Which US states have no sales tax?
Five states have no statewide sales tax: Alaska, Delaware, Montana, New Hampshire, and Oregon. Alaska is a special case — the state charges nothing, but local municipalities can add their own rate.
Does Amazon collect tax on my order?
Yes, in all 45 states with a sales tax. After the 2018 South Dakota v. Wayfair ruling, marketplaces like Amazon must collect based on the shipping address's combined rate, not their headquarters state.
How do I reverse-calculate tax from a total?
Divide the total by (1 + Tax% / 100). A $54.05 receipt in a 8.1% tax zone: 54.05 / 1.081 = $50.00 pre-tax, so tax = $4.05.
Is tax charged on tips?
No — in the US, tips are voluntary payments to the server and are not subject to sales tax. Restaurant tax is calculated on the pre-tip subtotal only.