Percentage Calculator
Find a percentage of a number, work out what percent one value is of another, calculate percentage increase, decrease or difference — pick a calculation type below.
Percentage Calculator
Provide any two values below and press Calculate to get the third.
Percentage Calculator in Common Phrases
Percentage Difference Calculator
Percentage Change Calculator
Provide any two of value, percent and result — the third is calculated for you.
Formulas used
X% of Y = (X ÷ 100) × Y
X is what % of Y = (X ÷ Y) × 100
% change = ((New − Old) ÷ |Old|) × 100
% difference = (|X − Y| ÷ ((X + Y) ÷ 2)) × 100
How to use this calculator
- Each box above is its own calculator — fill in the values it asks for (leaving the one you want solved for blank, where that's an option) and press its Calculate button.
- The top box and the Percentage Change Calculator can solve for any of their blanks — fill in two, leave one empty.
- The three "Common Phrases" boxes and the Percentage Difference Calculator each solve one specific, fixed question.
- Use each box's Clear button to reset just that calculator.
Understanding percentages
A percentage is just a way of expressing a fraction out of 100 — "45%" is shorthand for "45 out of every 100," which is the same amount as the fraction 45/100 or the decimal 0.45. Percentages show up everywhere because they let you compare proportions at a glance without worrying about the actual size of the numbers behind them: "20% off" means the same relative saving whether the item costs $10 or $10,000.
To turn any ratio into a percentage, divide the part by the whole and multiply by 100. Say a bag holds 40 marbles and 14 of them are blue — the fraction of blue marbles is 14/40 = 0.35, and multiplying by 100 gives 35%. That's exactly what the "X is what percent of Y" mode above does for you.
The core percentage formula
Every percentage question boils down to the same relationship between three numbers: a percentage (P), a base value it's applied to (V1), and the result (V2):
P × V1 = V2
Depending on which two of those three values you already know, you rearrange the formula to solve for the third:
- Know P and V1, want V2 → multiply: V2 = P × V1 (this is "what is X% of Y")
- Know V1 and V2, want P → divide: P = V2 ÷ V1 (this is "X is what percent of Y")
- Know P and V2, want V1 → divide: V1 = V2 ÷ P
The calculator above always works with P written as a percent (e.g. "35"), and converts it to and from decimal form (0.35) internally so you never have to do that conversion by hand.
Percentage difference vs. percentage change
These two sound similar but answer different questions, which is why they're separate modes above:
Percentage difference treats two values as equals with no "before" or "after" — it measures how far apart they are relative to their average, so it gives the same answer no matter which value you list first:
% difference = |V1 − V2| ÷ ((V1 + V2) ÷ 2) × 100
For example, comparing 10 and 6: the gap is 4, and their average is 8, so the difference is 4 ÷ 8 = 50%.
Percentage change (and its two special cases, increase and decrease) treats one value as the original and the other as the result of a change, so order matters — swapping the two numbers flips the sign:
% change = (New − Old) ÷ |Old| × 100
Going from 300 to 330 is a +10% change (an increase), but going from 330 to 300 is roughly a −9.1% change (a decrease) — the same two numbers, a different answer, because the direction matters.
Applying a percentage increase or decrease
To find the result of increasing or decreasing a number by a given percentage, convert the percentage to a decimal and add it to (or subtract it from) 1, then multiply:
Increase: New = Original × (1 + P÷100)
Decrease: New = Original × (1 − P÷100)
So $300 increased by 10% is 300 × 1.10 = $330, and $300 decreased by 10% is 300 × 0.90 = $270.
FAQ
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 15% of 200 is (15 ÷ 100) × 200 = 30.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 30 is what percent of 200? (30 ÷ 200) × 100 = 15%.
How is percentage increase or decrease calculated?
Subtract the original value from the new value, divide by the original value, then multiply by 100. A positive result is an increase; a negative result is a decrease.
What's the difference between "percentage change" and "percentage difference"?
Percentage change compares a "before" and "after" value, so the order you enter them in matters. Percentage difference treats both values as equals and measures the gap relative to their average, so it gives the same result either way round.
Can this calculator handle negative numbers?
Yes, for percentage change calculations. For "percent of" calculations, enter positive values for a meaningful result.
Is this percentage calculator free?
Yes, it's completely free with no sign-up required.