Sales tax makes up about 25 percent of state and local government revenues, according to the U.S. Census Bureau. When you buy an item, merchants add a certain percentage of the item's price to pay for the sales tax. You can quickly calculate how much money you will have to pay using a calculator. To perform this calculation, you need to know the price of the item and the sales tax percentage for your area.

### Step 1

Find out the total sales tax percentage in your area. In some areas, you may have to pay a local sales tax as well as a state sales tax. For example, if the state sales tax equals 4 percent and the local sales tax equals 1.5 percent, the total sales tax would be 5.5 percent.

### Step 2

Divide the sales tax percentage by 100 to convert it from a percentage to a decimal. For example, if the sales tax percentage is 5.5 percent, use the calculator to divide 5.5 by 100 to get 0.055.

### Step 3

Add 1 to the sales tax expressed as a decimal from step 2. For example, if you had 0.055, you would add 1 to get 1.055.

### Step 4

Multiply the result from step 3 by the price of the item to add the tax to the price of the item. For example, if an item's listed price without tax is $34, you would multiply $34 by 1.055 to find that the total price with tax added would be $35.87.