Calculating Tips and Totals
Introduction
Welcome back to Shopping and Spending with Percentages! So far in this course, you have tackled discounts, sale prices, and sales tax — percentages that appear on the price tag and at the register. In this third lesson, we shift from the checkout counter to the table: calculating a tip.
Tipping comes up almost every time you eat at a restaurant, visit a hair salon, or use a delivery service. By the end of this lesson, you will be able to compute a tip at common rates such as 15%, 18%, and 20%, and determine the total amount paid by adding the tip to the original bill. The math follows the same multiply-then-add pattern you used for sales tax, so the steps will feel familiar right away.
What Is a Tip?
A tip (also called a gratuity) is an extra amount of money given to a service worker on top of the bill. In the United States, it is customary to leave a tip at restaurants, hair salons, and for services like food delivery or rideshares. The tip is calculated as a percentage of the pretax bill — the total for the food or service before any sales tax is applied.
The most widely used tip rates are 15%, 18%, and 20%. A 15% tip is generally seen as the starting point for acceptable service, 18% reflects solid appreciation, and 20% is a common choice for great service. Knowing how to calculate each of these quickly is a practical everyday skill, and the technique is one you already have: convert the percent to a decimal and multiply.
Calculating the Tip Amount
Finding a tip is a single conversion followed by a single multiplication — the same approach you used for sales tax in the previous lesson.
Let's say your dinner bill is $50.00 and you want to leave an 18% tip.
Step 1 — Convert the rate:
Step 2 — Multiply:
The tip is $9.00. One conversion and one multiplication — that is all it takes.
Comparing Common Tip Rates
To build a feel for what each rate means in real dollars, let's compare all three standard rates on the same $65.00 restaurant bill.
| Tip Rate | As a Decimal | Calculation | Tip Amount |
|---|---|---|---|
| 15% | 0.15 | $9.75 | |
| 18% | 0.18 | $11.70 | |
| 20% | 0.20 | $13.00 |
On a $65 bill, the difference between a 15% tip and a 20% tip is only $3.25. Seeing all three side by side helps you gauge how much each percentage point really costs — and makes choosing a rate at the table much less stressful.
