Sales Tax Calculator

How it works

Sales tax is a flat percentage of the pre-tax price. Multiply the price by the rate to get the tax, and add it to the price to get what you pay at the register.

Going the other way is the common mistake. If a receipt total already includes 8% tax, the tax is not 8% of the total; it is 8% of the smaller pre-tax price. Divide the total by 1.08 to recover the pre-tax price, and the tax is the difference.

The rate is whatever you enter. Combined state, county and city rates vary by address, so take the rate from a recent receipt or your state's tax authority and type it in as a percent.

Formula

r = rate ÷ 100
add:      tax = price × r         total = price × (1 + r)
reverse:  price = total ÷ (1 + r)   tax = total − price

Example

A $100 item at 8% sales tax: the tax is 100 × 0.08 = $8.00 and the total is $108.00.

A receipt total of $108.00 at 8%: the pre-tax price is 108 ÷ 1.08 = $100.00 and the tax was $8.00. Taking 8% of $108 instead would wrongly give $8.64.

A $59.99 item at California's 7.25% statewide base rate: tax 59.99 × 0.0725 = $4.35 and a total of $64.34.

Assumptions and limitations

• One flat rate applies to the whole amount. Items taxed at different rates, exemptions and tax-free thresholds are not modelled.
• No rate lookup is performed. The rate you enter is used as given; check it against your state or local tax authority.
• Figures are shown rounded to the cent; retailers may round each line item differently from a single rounding of the total.
• This is an arithmetic aid, not tax advice.

Frequently asked questions