Add a sales tax rate to a subtotal to see the tax amount and final total.
Usage Tip
For a tax-inclusive price, divide the total by (1 + tax rate) to get the subtotal.
Sales tax is the subtotal multiplied by the tax rate, and the total is the subtotal plus the tax. To work backward from a price that already includes tax, divide the total by one plus the rate written as a decimal, so a total of 107 at 7 percent tax has a pre tax price of 100.
Rates vary by location and often combine a state rate with city or county taxes, and some goods, such as groceries or clothing, are exempt in certain places. Stores may round the tax on each item or on the whole bill, so the total can differ by a cent or two. Check with your local tax authority for the exact rules that apply to you.
At a 7 percent rate, a 40 dollar subtotal has 2.80 in tax, for a total of 42.80. A 250 dollar purchase at 8.25 percent carries 20.63 in tax and totals 270.63. Adding the tax rates for the state and the locality gives the combined rate where both apply.
To estimate tax in your head, find ten percent of the subtotal by moving the decimal one place, then adjust. Round only the final total, since rounding at each step can shift the answer by a cent. Keep receipts for any purchase you may need to document for business use.