Math calculators
Percentages, percentage change, and quick everyday math.
Math tools
Use these calculators for general informational estimates and simple arithmetic. Check the formula, units, examples, and limitations on each calculator page before relying on a result.
Percentage calculator
Calculate percentage of a value, part-of-whole percentage, reverse percentages, add/subtract percentages, and percentage change with guided modes.
Percentage change calculator
Calculate percentage increase or decrease between a starting value and a new value, with direction and absolute difference.
How to use this category
- Choose the calculator that matches the task and units you have.
- Enter realistic values from your receipt, recipe, schedule, room measurement, appliance label, or trip plan.
- Read the visible formula, result breakdown, and assumptions before using the estimate.
Related categories
Estimate boundaries
These tools do not replace qualified professional review. Use them for transparent arithmetic, quick checks, and low-stakes planning only.