Whats the Sales Tax? United States, adds or deduct tax easily. Simply select the Add Tax Calculator tab and insert the product pricing and the state tax rate, and let the app automatically calculate and reveal the equation formula and the new product pricing with tax OR alternatively use the Minus State Tax Calculator to work out what the value of a product was BEFORE-TAX was added. Included is a State Sales Tax Map which shows you the levels of State Tax in each state and you can drill down further to find the exact state sales rate for your state. Information about the United States State Sales Tax Rate included.