How to Calculate Percentage Increase and Decrease

A practical guide to percentage change with simple examples for shopping, finance, business and everyday calculations.

Why this matters

Understanding the basics helps you choose the right tool and interpret results more confidently. Affivance tools are designed to make common calculations and transformations easier to perform in a browser.

Start with the right inputs

Use accurate, consistent inputs and check units before calculating. Small input errors can produce results that look reasonable but are still incorrect.

Use an Affivance tool

After understanding the basics, use the relevant browser-based tool to run the calculation or transformation quickly. Core tools do not require an API key.

Check the result

For important financial, health or business decisions, treat online calculator results as estimates and verify important assumptions independently.

Related tools and guides

Browse all Affivance tools or read more guides in the Affivance Blog.