Percentage Guides

How to Calculate a Percentage

The core formula, three calculation types, and mental math shortcuts for everyday use.

How to Calculate Percentage Change

Measure increases and decreases with the right formula -- for prices, scores, and statistics.

How to Calculate Percentage Difference

Compare two equal-status values symmetrically without a defined starting point.

Percentage vs Percentage Points

One of the most common sources of confusion in statistics and financial reporting -- explained clearly.

How to Calculate a Tip

Fast mental math for 15%, 18%, and 20% tips -- plus bill splitting and group situations.

How to Calculate a Discount

Find any sale price instantly, handle stacked coupons, and spot the deals that are actually good.

How to Calculate Sales Tax

Calculate tax on any purchase, find the pre-tax price, and understand what you actually pay.

How to Calculate Profit Margin

Gross, operating, and net margin -- the three numbers every business owner should understand.

Margin vs Markup

Both measure profit but from different bases. Confusing them leads to systematic under-pricing.

How to Calculate Grade Percentage

Convert raw scores to percentages, understand weighted grades, and find out what you need to pass.