Percentage Calculator
Calculate percentages, reverse percentages, and percentage change with formula display.
What is Percentage Calculator?
A percentage calculator is a free online tool that helps you solve percentage-related math instantly. Whether you need to find what 20% of 150 is, determine what percent 25 is of 100, or calculate the percentage change between two values, this tool handles it all. It runs entirely in your browser with no signup required and no data sent to any server.
Real-world use cases include calculating sales discounts (e.g., 30% off a $80 item), computing restaurant tips (15% or 20% of the bill), analyzing profit margins, comparing before-and-after metrics, and working with tax rates. Students, shoppers, business analysts, and anyone doing quick percentage math will find it indispensable.
How to Use Percentage Calculator
- Choose a mode: A% of B (find a percentage of a number), A is what % of B (reverse percentage), or % Change (increase/decrease between two values).
- Enter the numbers in the labeled fields. Placeholders show example values for each mode.
- Click Calculate or press Ctrl+Enter. The result appears instantly with the formula displayed.
- Use Use Sample to load example values and see how each mode works.
- Click Copy to copy the equation, or Clear to reset and start over.
Tips & Best Practices
Use Ctrl+Enter to calculate without clicking. Use Ctrl+Shift+C to copy the result. Press Esc to clear all fields. The stat grid shows Result, Formula, Decimal, and Direction (for % Change mode). For percentage change, B is the original value and A is the new value — the tool computes ((A − B) / |B|) × 100. In "A is what % of B" mode, B must be non-zero. For decimal conversions, try our unit converter.
When to Use This Tool
Use the percentage calculator when you need quick answers for discounts, tips, tax, profit margins, growth rates, or any percentage math. Pair it with the currency converter for international pricing, or the unit converter for non-percentage conversions.
Frequently Asked Questions
What is a percentage calculator?
A percentage calculator is a tool that helps you compute percentage-related math: finding what percent one number is of another, calculating a percentage of a value, or determining percentage change between two numbers. ToolCrux's calculator runs entirely in your browser.
How do I find what percentage A is of B?
Enter A and B in the fields, then click A is what % of B. The result shows the percentage. For example, if A is 25 and B is 100, the answer is 25%.
How do I calculate percentage change?
Enter the original value as B and the new value as A, then click % Change B → A. The tool computes ((A - B) / B) × 100 to show the percent increase or decrease.
Can I use this for discounts and tips?
Yes. Use A% of B for discounts (e.g., 20% of 50) or tips (e.g., 15% of a bill). For reverse calculations, use A is what % of B. Try our unit converter for other conversions.
Is the percentage calculator free?
Yes. The ToolCrux percentage calculator is free, runs in your browser with no signup, and keeps all calculations private. No data is sent to any server.