TetraKits
Solve three common percentage problems in one tool: what is X% of a number, what percent X is of Y, and percent increase or decrease between two values. Enter values and read results instantly. The TetraKits Percentage Calculator runs entirely in your browser — free, private, and ready on mobile or desktop.
Overview
Tips, tax rates, grade curves, and growth metrics phrase the same math three different ways. Switch modes to solve "X% of Y," "X is what % of Y," or percent change without relearning formulas.
How to use the percentage calculator
- Choose calculation type — Select % of (what is 20% of 80?), what % (15 is what % of 60?), or change (percent increase/decrease).
- Enter your values — Type the numbers for your problem. Results update as you type.
- Read the answer — See result with formula explanation. For sale pricing, use the discount calculator.
Common use cases
- Choose calculation type: Select % of (what is 20% of 80?), what % (15 is what % of 60?), or change (percent increase/decrease).
- Enter your values: Type the numbers for your problem.
- Read the answer: See result with formula explanation.
- Bookmark for quick access: Save the tool for repeat tasks without installing an app.
Frequently asked questions
How do I find what percent one number is of another?
Select "what %" mode. Enter the part and the whole. Result = (part ÷ whole) × 100. Example: 15 of 60 = 25%.
How is percent increase calculated?
Percent change = ((new − old) ÷ old) × 100. A rise from 80 to 100 is a 25% increase.
Can I calculate X% of a number?
Yes. Select "% of" mode, enter the percentage and base number. 20% of 150 = 30.
What about negative percent change?
A decrease produces a negative percent change. Dropping from 100 to 80 is −20%.
Is this percentage calculator free?
Yes. Unlimited calculations with no signup.
