Percentage Calculator
Solve every common percentage problem: X% of Y, what percent one number is of another, percentage increase or decrease and reverse percentage.
Inputs
Formula
- Part = (P / 100) × Whole
- P = (Part / Whole) × 100
- Change % = ((New − Old) / Old) × 100
- Whole = Part / (P / 100)
A percentage is a ratio expressed per hundred. Every percentage question is one of four rearrangements of Part = Rate × Whole. Identifying which of the three quantities is unknown tells you which form to use — the calculator does that selection for you.
Step-by-step calculation
Rate as a fraction
P / 100
0.15
Part
(P / 100) × Whole
30
Worked example
- What is 15% of 200? Part = (15 / 100) × 200 = 30.
- Price rises from 200 to 230 → change = (30 / 200) × 100 = +15%.
- 30 is 15% of what? Whole = 30 / 0.15 = 200.
Tips
- A 20% fall followed by a 20% rise does not return to the start — you end 4% lower, because the base changed.
- For successive discounts, multiply the remaining fractions: 30% then 20% off = 0.7 × 0.8 = 0.56, i.e. 44% off.
Frequently asked questions
How do I calculate a percentage increase?
Subtract the old value from the new value, divide by the old value and multiply by 100. A negative result is a decrease.
How do I remove a percentage from a total?
Divide by (1 + rate). To strip 18% tax from 118, compute 118 / 1.18 = 100.
What is the difference between percent and percentage point?
A move from 5% to 7% is a rise of 2 percentage points, but a 40% relative increase.
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