🔢 Basic percentage calculators

Written by Rohan Mehta Updated
Editorial details Reviewed by Vikram Sen Verified · Methodology · Accuracy policy

Quick answer

Core percent math: what is X% of Y, reverse percentage, increase/decrease, averages, and comparisons—each formula on its own page.

What is r% of B: (r / 100) × B · X is what % of Y: (X / Y) × 100 · Increase B by r%: B × (1 + r/100)

Best for: Homework, spreadsheets, shopping discounts, survey shares, tip estimates.

Also see: Change calculators · Conversions · Percentage guide

Start with the sentence you have—percent of a number, what percent one value is of another, or change by a rate—then open the matching tool below.

Key facts

Percent of base (rate ÷ 100) × base when the rate applies to a single reference value.
Category Mathematics / everyday arithmetic
Related concepts Reverse percentage, successive change, fraction and decimal conversion.

Definitions

Percent of a number

Multiply the base by (rate ÷ 100); the rate is always relative to that base unless stated otherwise.

Reverse percentage

Recover an original value before a known percent was applied—denominator choice matters.

Comparison table

Topic Guidance
Percent of vs percent change Percent of uses one base; change compares two values over time.
Average of percents Simple average of rates can mislead when denominators differ—see the average tool notes.

❓ Frequently Asked Questions

Which basic calculator should I use first?

Use “what is X% of Y” for share-of-total problems and “X is what percent of Y” when you already have two values.

Where are fraction-specific pages?

Pages like “3/20 as a percent” are long-tail entry points; they link back to these core tools for the general method.

Glossary references

Pair percent language with conversion pages when you mix fractions, decimals, and ratios.