Percentage Calculator
Calculate a percentage of a number, what percent one value is of another, and percentage increase or decrease with clear formulas and results.
What this tool solves
Calculate a percentage of a number, percentage relationships and percentage increase or decrease.
Input: the values involved in a percentage, ratio or before/after comparison.
Output: percentage values, amounts or percentage change.
How to use it
- Choose the calculation that matches your question: percent of a value, value as a percent, or change between two values.
- Enter the numbers using the same unit where a comparison is required.
- Read the result and formula; for financial or reporting work, keep the original values with the calculation.
Common use cases
- Calculate discounts, tax percentages and markups
- Measure growth or decline between two values
- Work out test scores, completion rates or proportions
Privacy, accuracy and limits
Percentage change from an original value of zero is undefined. Rounding can make displayed results differ slightly from spreadsheet or financial-system rules.
WebToolMint keeps this workflow local in the browser where the feature allows it. Network-dependent tools are labelled separately. Keep originals and independently verify results that affect legal, financial, medical or business decisions.
Frequently asked questions
How do I calculate 20% of 150?
Multiply 150 by 0.20; the result is 30. The calculator can do this directly.
What is the percentage change formula?
For a non-zero starting value: (new − old) ÷ old × 100.
Why is percentage change undefined from zero?
The formula divides by the original value. Division by zero is undefined, so there is no finite conventional percentage change from zero.
Browse Calculators & Converters