Sales tax is usually a percent of the taxable pretax price. You multiply the pretax amount by the rate, then add the tax to get the amount due at checkout under a simple model.
Core idea
Tax = pretax × (rate ÷ 100)
Total = pretax + tax
Sample
$100 · 8% → tax $8.00, total $108.00. Open sample
Related
Frequently asked questions
How is sales tax calculated?
Multiply the pretax amount by the tax rate percent, then add tax to pretax for the total.
Sample 8% on $100?
Tax about $8.00; total about $108.00.
Sources linked above include U.S. government materials (for example CFPB, FDIC, NCUA, BLS, IRS) where noted. Sample math uses only labeled Nestfigure assumptions—not bank quotes, job offers, or personalized advice. Last reviewed: August 9, 2026.