Percentage calculator
A little less mental maths. Get the number you need, instantly.
20% of 150 = 30
Use this tool in your workflow
A protected JSON endpoint for scripts and AI tools. Execution is disabled by default and requires an approved account and bearer API key.
GET /api/tools/percentage?mode=of&a=20&b=150{ "result": 30, "unit": "number" }Modes: of, what, change. Both a and b must be finite numbers. Invalid input returns HTTP 400.
What it does
Calculate percentages, percentage shares and percentage changes for free, directly in your browser.
How to use it
- Choose percentage of, what percentage, or percentage change. Enter both numbers to calculate.
- Copy the result when ready. A zero starting value has no defined percentage change.
Example
20% of 150 is 30. Increasing 100 to 120 is a 20% change.
Methodology
Percentage of: a × b ÷ 100. Share: a ÷ b × 100. Change: (b − a) ÷ |a| × 100.
Limitations
Finite numbers only. Undefined divisions are rejected. Results use floating-point precision.
Automation
A protected JSON API is documented for this tool. Execution requires deployment enablement and an approved account’s API key.
View capabilities and documentationReference updated
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