You walk into a store and see a jacket with a price tag of $50. You grab it and head to the register, expecting to pay $50. But when you check out, the total is $54.00. Where did the extra $4 come from? Sales tax. The price on the tag doesn't include the tax that gets added at checkout. But sales tax rates vary wildly by location—from 0% in some states to over 10% in others. Some cities have additional local taxes. Some items are taxed; others are exempt. You could try to calculate it mentally. But without knowing the exact local tax rate, the calculation is a guess. Or you could use a sales tax calculator to instantly show that a $50 purchase in your location will cost exactly $54.00 (assuming an 8% sales tax rate). A sales tax calculator computes the total amount of tax owed on a purchase by applying the appropriate state, county, and local tax rates to the item price. It shows both the tax amount and the final total cost, and can work backward to show the pre-tax price if you kn...