Calculating sales tax in Washington is straightforward. You multiply the price of the item by the combined sales tax rate for your location, then add that number to the original price.
The combined rate has two parts. The state rate is 6.5 percent everywhere in Washington. The local rate varies by city and county. Your total rate is the sum of both.
The basic formula
Here is the formula for any purchase in Washington:
Sales tax amount = Price × Combined rate (as a decimal)
Total cost = Price + Sales tax amount
To turn a percentage into a decimal, move the decimal two places left. For a 10.25 percent rate, that is 0.1025. For an 8.9 percent rate, that is 0.089.
Step by step example
Let us say you live in Spokane, where the combined rate is 8.9 percent. You buy a new coat for $75.
- Step one: Convert 8.9 percent to a decimal. That is 0.089.
- Step two: Multiply $75 by 0.089. That equals $6.675. Round to the nearest cent, which is $6.68.
- Step three: Add $6.68 to $75. Your total is $81.68.
That is all there is to it.
How to find your local combined rate
You need to know your local rate before you can calculate the tax. Here is how to find it. The easiest way is to look at a recent receipt from a store in your neighborhood. The receipt usually shows the total sales tax rate. It might say something like "Tax 10.25 percent" near the bottom.
You can also use the lookup tool on the Washington State Department of Revenue website. Enter your address and it will tell you the exact combined rate.
Or you can memorize the rate for your city. Most cities in Washington have rates between 8.0 and 10.25 percent. The table below shows common rates.
Calculating tax on multiple items
If you buy several items at once, you have two options.
You can calculate tax on each item separately and add them up. That works fine but takes longer.
The faster way is to add up the prices of all taxable items first, then apply the tax rate once. For example, if you buy a $50 shirt, a $30 book, and a $120 lamp, your total before tax is $200. Multiply $200 by your local rate to get the total tax.
One thing to watch for. Some items are not taxable at all. Groceries are exempt from sales tax in Washington. Prescription drugs are exempt. If you buy a mix of taxable and non-taxable items, only apply the tax to the taxable ones.
Sometimes you have the total price after tax and you want to know how much tax you paid. This is useful for expense reports or figuring out your deduction.
Divide the total price by one plus the tax rate as a decimal. Then subtract the original price.
For example, you bought something in Seattle and the total was $110.25. The combined rate is 10.25 percent, or 0.1025. Add 1 to that to get 1.1025. Divide $110.25 by 1.1025. You get $100. That was the price before tax. Subtract $100 from $110.25 to find the tax amount, which is $10.25.
Calculating tax on a car purchase
Cars are a special case because you pay the tax when you register the vehicle, not when you buy it from a private party.
If you buy from a dealer, the dealer handles the tax calculation for you. They use the combined rate for your home address.
If you buy from a private party, you pay use tax at the same rate as sales tax. The Department of Licensing calculates it for you when you register the car. They use the purchase price or the fair market value, whichever is higher.
For example, you buy a used car from a neighbor in Spokane for $10,000. The combined rate is 8.9 percent. The tax is $890. You pay that when you get your license plates.
Calculating tax on online purchases
Online purchases are taxed the same as in-store purchases in Washington. The seller is supposed to charge you the combined rate for your delivery address.
When you check out on Amazon or another large retailer, the site calculates the tax for you automatically. You do not need to do anything.
If you buy from a small online seller that does not collect Washington tax, you are technically supposed to report the purchase on your annual use tax return and pay the tax yourself. The calculation is the same as sales tax. Multiply the price by your local combined rate.
Frequently Asked Questions (FAQ)
How do I calculate sales tax in Washington on a $100 purchase?
Multiply $100 by your local combined rate. In Seattle at 10.25 percent, tax is $10.25 and total is $110.25. In Spokane at 8.9 percent, tax is $8.90 and total is $108.90. In a rural area with only the state rate of 6.5 percent, tax is $6.50 and total is $106.50.
What is the sales tax rate for my address in Washington?
You can find your exact combined rate using the lookup tool on the Washington State Department of Revenue website. Enter your address and the tool will show the state rate plus all local taxes that apply to your location. Most cities have rates between 8.0 and 10.25 percent.
Do I calculate sales tax on groceries in Washington?
No. Groceries are exempt from sales tax in Washington. You do not add any tax to raw ingredients, produce, meat, dairy, bread, or other basic food items. Prepared food from restaurants and delis is taxable. Hot food is always taxable. Cold prepared food is usually taxable as well.
How do I calculate sales tax on a car in Washington?
If you buy from a dealer, the dealer calculates the tax for you using your home address rate. If you buy from a private party, the Department of Licensing calculates the use tax when you register the vehicle. The rate is the same as your local sales tax rate. The tax is based on the purchase price or the fair market value, whichever is higher.
Do I need to calculate sales tax on online purchases?
No. Most large online retailers like Amazon calculate the tax for you automatically. They use your delivery address to apply the correct combined rate. You do not need to do any math. If you buy from a small seller that does not collect tax, you are supposed to calculate and pay use tax yourself on your annual state return.
What is the easiest way to calculate sales tax in Washington?
The easiest way is to use a sales tax calculator online. Enter the price and your zip code, and the calculator does the math for you. Many people also just memorize the total rate for their city and use the formula price times rate. For everyday small purchases, the difference of a few cents does not matter much.