Tip and Discount Basics: Percent Off the Right Base
Everyday percent math fails when the base is wrong: tip on pre-tax vs post-tax, discount on list vs sale price, or stacked coupons applied in the wrong order. This guide keeps the bases explicit and points to the matching calculators.
Tips
Tip amount = bill × (tip% ÷ 100). Decide whether your bill base includes tax and whether you tip on the pre-discount subtotal—local norms differ. Split tips by dividing the tip (or the tipped total) by the number of people.
Discounts
A single discount multiplies price by (1 − discount%/100). Stacked discounts usually apply sequentially, not as a sum of percents. A 20% then 10% off is not 30% off.
Quick checks
Confirm the base
Pre-tax, post-tax, or list price.
Apply one percent
Use the tip or discount calculator.
Stack carefully
Apply discounts one after another if that is how the store posts them.