Percentage Calculator – Percent, Increase & Decrease
Calculate X% of a value, what percentage one value is of another, and percentage increase or decrease with clear zero-baseline validation.
The word percent means out of one hundred, but not all percentage questions are alike. Finding 15% of 200, finding what percent a part represents, and measuring the change between old and new values use different denominators. Identify the question before entering values.
How it works
Percentage amount = percent ÷ 100 × base. Part as percent = part ÷ whole × 100 when whole is nonzero. Relative change = (new − old) ÷ old × 100 when old is nonzero.
Example
15% of 200 equals 30. A price rising from 200 to 230 increases by 15%; returning from 230 to 200 decreases by approximately 13.04% because the starting base changes.
How to use
- Choose the percentage question that matches your task: percent of an amount, part of a whole or change between values.
- Enter the percentage and base amount, or old and new values, with the correct direction and units.
- Check which value is used as the denominator and distinguish a percent change from a percentage-point change.
Key features
- Percent-of-number and change concepts
- Clear denominator and starting-base explanations
- Worked financial and classroom examples
Common uses
- Understand exam marks percentages
- Calculate a sale discount amount
- Compare budget or price changes
Limitations to know
A zero original value makes the usual relative percentage change undefined. A rise from 20% to 30% is 10 percentage points, not a 10% relative increase; the latter is 50% in that example.
Frequently asked questions
What is 15% of 200?
Multiply 200 by 0.15 to obtain 30.
Why do a 15% rise and a 15% fall not cancel?
The fall is calculated using the new, larger amount. The base of the second percentage is different.
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