Everyday Life Reference

Common Percentage Calculations for Shopping

Published September 8, 2026

The percentage calculations that come up most often while shopping. For the underlying math, see How to Calculate a Percentage.

Scenario How to Calculate
Discount amount Price × (Discount % ÷ 100)
Price after discount Price × (1 − Discount % ÷ 100)
Sales tax total Price × (1 + Tax % ÷ 100)
Tip amount Bill × (Tip % ÷ 100)

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Frequently Asked Questions

How do I quickly estimate 20% off in my head?

Find 10% by moving the decimal point one place left, then double that number.

Does “percent off” apply before or after tax?

It depends on the store, but discounts are typically applied to the pre-tax price first, and tax is then calculated on the discounted amount.

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