Sales Tax — Definition, Formula & Examples
Sales tax is a percentage of a purchase price that gets added to the cost of an item, collected by the seller and paid to the government. You calculate it by multiplying the item's price by the tax rate (written as a decimal).
Sales tax is a consumption tax expressed as a fixed percent of the pre-tax price. If an item costs dollars and the tax rate is , the tax amount is , and the total cost paid by the buyer is .
Key Formula
Where:
- = The pre-tax price of the item (in dollars)
- = The sales tax rate (as a percent)
How It Works
To find the sales tax on a purchase, convert the tax rate from a percent to a decimal and multiply it by the item's price. For example, a 7% tax rate becomes 0.07. Multiply the price by 0.07 to get the tax amount, then add that tax to the original price for the total cost. You can also skip straight to the total by multiplying the price by 1.07 (that is, 1 plus the decimal rate). This shortcut works because you are combining 100% of the price with 7% of the price in a single step.
Worked Example
Problem: A skateboard costs $80. The sales tax rate is 6%. What is the tax amount, and what is the total cost?
Step 1: Convert the tax rate to a decimal by dividing by 100.
Step 2: Multiply the price by the decimal tax rate to find the tax amount.
Step 3: Add the tax to the original price to find the total cost.
Answer: The sales tax is $4.80, and the total cost is $84.80.
Another Example
Problem: You paid $53.50 total for a pair of shoes, and the sales tax rate was 7%. What was the pre-tax price?
Step 1: The total cost equals the price times (1 + tax rate as a decimal). Set up the equation.
Step 2: Divide both sides by 1.07 to isolate the pre-tax price.
Answer: The pre-tax price of the shoes was $50.00.
Visualization
Why It Matters
Calculating sales tax is one of the most practical percent skills you will use in everyday life — every time you buy something in a store, you need to estimate what you will actually pay. In middle-school math courses, sales tax problems appear alongside discount and commission as core percent applications. Careers in retail, accounting, and business all require fluency with these calculations.
Common Mistakes
Mistake: Forgetting to convert the percent to a decimal before multiplying.
Correction: Always divide the tax rate by 100 first. For example, 6% becomes 0.06, not 6. Multiplying $80 by 6 gives $480, which is clearly too large.
Mistake: Subtracting the tax from the total to find the pre-tax price instead of dividing.
Correction: If you know the total and the rate, divide by (1 + rate as a decimal). Subtracting the tax percentage of the total gives an incorrect result because the tax was calculated on the pre-tax price, not on the total.