Free Online Percentage Calculator
Find X% of Y, what percent X is of Y, or the change between two values
Result
30
Formula
(15 / 100) × 200 = 30
Try these next
Why use Percentage Calculator
- Three calculation modes in one tool: X% of Y, what % X is of Y, and percentage change.
- Every result comes with the formula using your actual numbers, so you can verify or learn the math.
- Updates as you type -- use it like a scratchpad for quick financial or homework calculations.
- Handles edge cases (changes from zero, results above 100%) without breaking.
- Direction is flagged clearly on percentage change -- positive for increase, negative for decrease -- no ambiguity.
How it works
Each mode applies a different arithmetic formula. 'X% of Y' multiplies the base value by the percentage divided by 100: result = Y * (X / 100). 'X is what % of Y' divides the part by the whole and multiplies by 100: result = (X / Y) * 100. Percentage change subtracts the old value from the new value, divides by the absolute value of the old value, and multiplies by 100: result = ((new - old) / |old|) * 100. A positive result indicates an increase, a negative result a decrease. The tool displays the formula with your actual numbers substituted in so you can follow each step. Results are rounded to a sensible number of decimal places.
About this tool
Three percentage problems come up over and over: what is X% of Y, what percent is X of Y, and what is the percentage change between two values? This calculator handles all three. Pick a mode, type your numbers, and the result updates as you type -- along with the formula using your actual values, so you can check the math or learn the method. The formulas themselves are simple. X% of Y is Y times (X / 100). X is what % of Y is (X / Y) times 100. Percentage change is ((new - old) / old) times 100, positive for increases and negative for decreases. The tricky part is doing them quickly under pressure -- during checkout, on a quiz, or in a meeting. Edge cases like a starting value of zero and results above 100% are handled without errors.
How to use Percentage Calculator
- Pick a mode. Toggle between 'X% of Y', 'X is what %', or '% Change'.
- Type your numbers. Enter values in the input fields. Results update live as you type.
- Check the formula. The answer appears with your actual numbers substituted into the formula.
Use cases
- Standing at a 30%-off rack trying to figure out the final price of a $149 jacket before heading to checkout.
- Scored 47 out of 60 on a quiz -- switch to 'X is what %' mode and see 78.3% without reaching for a calculator app.
- Comparing this month's revenue ($18,400) against last month ($15,200) for a report to your accountant -- percentage change mode shows a 21.1% increase.
Frequently Asked Questions
Divide the part by the whole and multiply by 100. For example, to find what percent 30 is of 200: (30 / 200) × 100 = 15%. Use the "X is what %" mode in the calculator above for instant results.
Percentage change = ((New Value - Old Value) / Old Value) × 100. A positive result means an increase, a negative result means a decrease. For example, going from 200 to 250 is a 25% increase.
Percentage change measures the relative change from an original value to a new value and has a direction (increase or decrease). Percentage difference compares two values without a defined starting point, using the average as the base.
Divide by 100. So 25% is 0.25, and 7.5% is 0.075.
Subtract the old value from the new value, divide by the old value, and multiply by 100. For example, from 80 to 100: ((100 - 80) / 80) × 100 = 25% increase.
Use the "X is what %" mode. Enter the discount amount as the value and the original price as the total. For example, a $30 discount on a $200 item: (30 / 200) × 100 = 15% discount.
Yes. A percentage greater than 100 means the value exceeds the reference amount. For example, if sales grew from 100 to 250, that is a 150% increase. A value of 300% of X means three times X.
Divide the result by the percentage and multiply by 100. For example, if 30 is 15% of the original number: 30 / 15 × 100 = 200. The original number is 200.
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