Percentage Calculator
Four calculators in one — find X% of a number, work out what percent one number is of another, measure a percentage increase or decrease, or add and subtract a percentage. Every answer comes with the working shown.
What is a percent of a number?
Show the working
The one formula behind every percentage
A percentage is just a fraction out of 100. Almost every percentage question reduces to a single relationship:
Percentage = (Part ÷ Whole) × 100
Rearranging that one equation answers every mode in this calculator. If you know the percentage and the whole, you find the part; if you know the part and the whole, you find the percentage; and if you compare two values, you find the change between them.
The four question types
1. What is X% of a number? Turn the percent into a decimal and multiply: 25% of 850 = 0.25 × 850 = 212.5. This is how you find a tax amount, a tip, or a share of a total.
2. X is what percent of Y? Divide the part by the whole and multiply by 100: 212.5 ÷ 850 × 100 = 25%. Use it for scores, completion rates and "what proportion" questions.
3. Percentage increase or decrease. Take the difference, divide by the original, and multiply by 100: from 850 to 900 is (50 ÷ 850) × 100 ≈ 5.88% up. A negative answer is a decrease. Always divide by the starting value, not the new one.
4. Add or subtract a percentage. Multiply by (1 + p/100) to add, or (1 − p/100) to subtract: 5000 + 18% = 5000 × 1.18 = 5900. This applies a markup, tax, tip or discount in a single step.
Percentage change vs percentage points
These two are easy to confuse. Percentage change is measured relative to the starting number, while a percentage-point change is the simple difference between two percentages. Moving from 10% to 15% is a rise of five percentage points, but a 50% percentage increase relative to the original 10%. When a headline mixes them up, the story can look very different from the reality.
Why the working is shown
Every result here comes with a step-by-step breakdown, so the tool doubles as a quick tutor — useful for checking homework, understanding a formula, or explaining a number to someone else. Your recent calculations are also saved locally in your browser so you can compare a few scenarios side by side; nothing is uploaded, and you can clear the list at any time.
Frequently asked questions
How do you calculate a percentage of a number?
Divide the percent by 100, then multiply by the number: 25% of 850 = 0.25 × 850 = 212.5. In general, (percent ÷ 100) × number.
How do I find what percentage one number is of another?
Divide the part by the whole and multiply by 100: 212.5 ÷ 850 × 100 = 25%. The formula is (part ÷ whole) × 100.
How do you calculate percentage increase or decrease?
((new − old) ÷ old) × 100. From 850 to 900 ≈ +5.88%. A negative result is a decrease — always divide by the original value.
How do I add or subtract a percentage from a number?
Add: number × (1 + percent/100). Subtract: number × (1 − percent/100). Adding 18% to 5000 = 5000 × 1.18 = 5900.
What's the difference between percentage change and percentage points?
Percentage change is relative to the starting value; a percentage-point change is the plain difference between two percentages. 10% → 15% is +5 points, but a 50% relative increase.