Percentage change
Use when one number is the starting point. A move from 80 to 100 is a 25% increase because the 20-point gain is compared with 80.
Every percentage formula in one place
Percentage Calculator
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Basic percentage
What is X% of Y?
Find a percentage amount from any number.
Answer
Your result
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Formula
Choose the right comparison
Three similar-sounding calculations answer different questions
The denominator determines the meaning. Use the original value for change, a symmetric average for difference, and simple subtraction for percentage points.
Percent difference
Use when neither value is the baseline, such as two measurements. Bobek compares the absolute difference with the average magnitude.
Percentage points
Use when both inputs are already percentages. A rate rising from 40% to 50% gains 10 percentage points and rises 25% relatively.
Practical percentage calculations
From quick homework checks to prices and business decisions
Shopping and bills
- Apply a discount before calculating tax.
- Add an optional tip and split the final bill.
- Reverse a sale price to recover the original price.
- Change the currency without changing the calculation.
Data and business
- Compare an old value with a new one and keep the direction.
- Separate percentage-point movement from relative growth.
- See margin and markup together to avoid confusing them.
- Copy the answer, formula and working for reports or notes.
Percentage questions
Percentage Calculator FAQ
How do I calculate a percentage of a number?
Divide the percentage by 100, then multiply by the number. For example, 15% of 80 is 0.15 × 80 = 12.
How do I find what percentage one number is of another?
Divide the part by the whole and multiply by 100. If 18 out of 24 items are complete, 18 ÷ 24 × 100 = 75%.
What is the formula for percentage change?
Percentage change is (new value − original value) ÷ |original value| × 100. The calculator reports whether the result is an increase or decrease. Conventional percentage change is undefined when the original value is zero.
What is the difference between percentage change and percent difference?
Percentage change compares a new value with an original reference value, so direction matters. Percent difference compares two values without treating either as the original; this calculator divides their absolute difference by the average of their absolute values.
What is a percentage point?
A percentage point is the arithmetic difference between two percentages. Moving from 20% to 25% is an increase of 5 percentage points but a relative increase of 25%.
How do I reverse a percentage increase or discount?
Divide the final value by the multiplier. After a 20% increase, divide by 1.20. After a 20% decrease, divide by 0.80. Subtracting 20% from a value that was increased by 20% does not return to the original.
What is the difference between margin and markup?
Both use profit, which is selling price minus cost. Margin divides profit by selling price; markup divides profit by cost. The same product therefore has different margin and markup percentages.
Are my values saved or uploaded?
No. Every calculation runs locally in your browser. Bobek does not receive or store the numbers you enter.