Sales Tax Calculator
- Rate as decimal: r = p / 100
- Forward (tax-exclusive): T = N × r ; G = N + T = N × (1 + r)
- Reverse (tax-inclusive): N = G / (1 + r) ; T = G − N = G × r / (1 + r)
- Find rate: p = 100 × (G − N) / N ; also p = 100 × T / N ; or p = 100 × T / (G − T)
Use this Sales Tax Calculator to add sales tax to a pre-tax price, remove tax from a tax-inclusive price, find the tax amount, or calculate the implied sales tax rate from known values.
Important: This calculator performs sales-tax arithmetic only. It does not determine whether a product or service is taxable or which state, local, city, or district tax rate applies.
Sales Tax Formula
First convert the sales tax percentage to decimal form:
Tax rate = sales tax % ÷ 100
When starting with a pre-tax price:
Sales tax = net price × tax rate
Gross price = net price + sales tax
Or directly:
Gross price = net price × (1 + tax rate)
Removing Sales Tax
If the entered price already includes sales tax:
Net price = gross price ÷ (1 + tax rate)
Sales tax = gross price − net price
Do not simply subtract the tax percentage from the gross price, because the percentage is normally applied to the pre-tax amount.
Finding the Sales Tax Rate
If the net and gross prices are known:
Sales tax rate = (gross price − net price) ÷ net price × 100
If the tax amount and net price are known:
Sales tax rate = tax amount ÷ net price × 100
Worked Example
Suppose an item costs $250 before tax and the applicable sales tax rate is 8%.
Sales tax:
$250 × 8% = $20
Final price:
$250 + $20 = $270
So the transaction has a $250 pre-tax price, $20 sales tax, and $270 tax-inclusive price.
To reverse the calculation:
$270 ÷ 1.08 = $250
$270 − $250 = $20 tax
Important Notes
- Sales-tax rates and taxable items vary by state and local jurisdiction.
- Some locations combine state, county, city, district, or other local taxes into the final rate.
- Even locations within the same ZIP code can sometimes fall under different taxing jurisdictions.
- Food, clothing, medicine, services, vehicles, digital products, and other purchases may receive different tax treatment depending on location.
- Tax holidays, exemptions, resale certificates, discounts, trade-ins, shipping charges, and special tax rules are not automatically considered.
- The calculator assumes the entered rate applies to the entire taxable net amount.
- Official invoices or point-of-sale systems may use specific rounding rules that create small differences.
- The currency selector changes the displayed currency label only and does not perform exchange-rate conversion.
- Use the applicable state or local tax authority’s current rate and rules for official transactions, accounting, or tax compliance.