Answer
30.00
Percentage Calculator
Work out everyday percentages: percentage of a number, percentage increase and decrease, and percent change between two values, each shown with its formula.
Key Terms (Click to expand)
Percentage (%)
A way to express a value as parts per hundred.
Base value
The denominator used to compute a percentage relationship.
Percent change
The signed change from start value A to end value B, relative to A.
Percentage points
Absolute difference between two percentages, not a relative percent change.
Tool
Percentage detail breakdown
| Mode | What is X% of Y? |
|---|---|
| Formula used | (X / 100) * Y |
| Explanation | Calculates what X percent of Y equals. |
Methodology
The calculator uses standard percentage formulas based on the selected mode:
- What is X% of Y:
(X / 100) * Y - X is what % of Y:
(X / Y) * 100 - % increase from A to B:
((B - A) / A) * 100 - % decrease from A to B:
((A - B) / A) * 100 - % change from A to B:
((B - A) / A) * 100
Using This Tool Well
When to use this tool
- Discount audit: confirm that a price drop from $100 to $80 is a 20% decrease, not a 25% decrease.
- Percentage-point translation: explain why a rate moving from 5% to 6% is a 1-point increase but a 20% relative increase.
- Share-of-total check: verify that $35 out of a $140 bill is 25% before splitting costs or quoting a ratio.
How to read the result
Read the result through the selected mode. If the sentence you want to say includes "of," "from," "to," or "change," match that wording to the mode before copying the number.
Common mistakes
- Switching direction: $80 to $100 is a 25% increase, while $100 to $80 is a 20% decrease, so using the wrong base changes the story by 5 percentage points.
- Dividing by zero: percent change from a base of 0 has no finite answer, so a "100% growth from zero" claim is not what the formula says.
- Mixing percent and percentage points: 5% to 6% is not "up 1%" in relative terms. It is up 1 percentage point or 20% relative to the old rate.
Reviewed by Leonardo, Software Engineer
Last reviewed June 23, 2026
Premises and Limitations
- Mode-specific formulas are applied exactly as entered, with no domain-specific adjustment rules.
- Some modes require a non-zero base value to avoid division-by-zero results.
- Negative values are allowed and can produce negative percentage outcomes.
FAQ
What is the difference between percent change and percentage points?
Percent change is relative to a base value, while percentage points are an absolute gap between percentages.
How do I calculate a discount percentage?
Use percentage decrease mode with original price as A and discounted price as B.
Can I use negative numbers?
Yes. Negative inputs are supported, but interpretation depends on context and selected formula mode.