What is X% of Y?
Use this to find an amount from a percentage and a base value, such as a discount amount, tip amount, or part of a total.
Free online calculator · no registration or login
Free Percentage Calculator Online
Calculate a percentage of a number, find what percent one value is of another, and work out percentage increase, decrease, change, or reverse values instantly.
- • Percent of and what percent
- • Increase and decrease
- • Apply and reverse change
- • Runs in this browser
Choose a percentage question
Each mode labels the value used as the baseline before you calculate.
Quick examples
Free online, no registration or login. Values stay in this browser while the calculation runs.
Your percentage result will appear here
Choose a mode and enter two values to see an answer, formula, and plain-language interpretation.
How to use the percentage calculator
The labels make the comparison baseline visible before you read the answer.
- Step 1
Choose the question you need to answer
Select percent of, what percent, percent change, apply change, or reverse percentage. Each mode names its baseline clearly.
- Step 2
Enter the two relevant values
Use whole numbers or decimals. For a percentage change, enter the original value first and the new value second.
- Step 3
Read the answer and formula
Review the result, calculation sentence, and formula. Copy it for notes or reset the workspace for another calculation.
How to choose a percentage calculation
The words in a percentage question tell you which value is the base. Choosing the right mode prevents a correct formula from answering the wrong question.
X is what % of Y?
Use this to turn a part-to-whole comparison into a percentage, such as a score out of a possible total.
Percentage increase or decrease
Use this when one value is the original baseline and the other is a later or new value.
Apply a percentage change
Use this to calculate a new value after an increase or decrease from a stated starting value.
Reverse a percentage change
Use this when you know the final value and the change that created it, but need the original amount.
How percentage formulas work
The result shows a concise formula so you can see which value was used as the base and how the percentage was converted.
Convert percent to a decimal
A percentage is divided by 100 before it is used as a multiplier. For example, 15% becomes 0.15.
Use the original value as the baseline
Percentage change is calculated relative to the original value: (new − original) ÷ original × 100. It is undefined when that original value is zero.
Undo a multiplier for reverse percentage
A final value after a change already includes a multiplier. Divide by 1 plus or minus the percentage as a decimal to recover the original value.
Everyday percentage checks
These modes handle ordinary arithmetic questions. They do not determine tax, pricing, lending, investment, or policy rules for you.
Find a discount amount
Use percent of to find the amount represented by a discount rate, then subtract it from the listed amount when that is the calculation you need.
Check a score or completion rate
Use what percent when a completed amount is compared with a known total, such as 45 out of 180.
Compare a previous and new value
Use percentage change when the first number is the stated starting point and direction matters.
Apply a markup or reduction
Use apply change to see a new amount after a percentage increase or decrease from a starting value.
Percentage change, difference, and points
Similar-sounding percentage terms can describe different baselines. Labeling the comparison correctly makes a result easier to interpret.
Percentage change needs a baseline
A directional change compares the new value with an original value. Reversing the inputs can produce a different percentage because the baseline changes.
Percentage difference is symmetric
Percentage difference treats two values as peers and divides their gap by their average. This tool does not present it as a substitute for directional percentage change.
Percentage points are not percent change
Moving from 40% to 44% is an increase of 4 percentage points. Relative to 40%, it is a 10% percentage increase.
Privacy and limits
Your values stay in this browser while the calculation runs. This free online tool requires no registration or login.
- Percentage change needs a nonzero original value.
- Displayed numbers are rounded for readability; calculations use the full entered decimal values.
- This calculator does not provide symmetric percentage difference, tax, pricing, finance, or legal advice.
Percentage Calculator FAQ
Straight answers about percentage formulas, change baselines, reverse calculations, and this tool's scope.
How do I calculate a percentage of a number?
Divide the percentage by 100, then multiply by the base number. For example, 20% of 150 is 0.20 × 150, or 30.
How do I find what percent one number is of another?
Divide the part by the whole, then multiply by 100. For example, 45 ÷ 180 × 100 equals 25%.
How do I calculate percentage increase or decrease?
Subtract the original value from the new value, divide by the original value, then multiply by 100. A positive answer is an increase and a negative answer is a decrease.
What happens when the original value is zero?
A percentage change from zero is undefined because the calculation would divide by zero. This tool shows a clear error instead of a misleading percentage.
Can a percentage be greater than 100%?
Yes. A part can be more than the reference whole, and a change can exceed 100% when the new value is more than double a nonzero original value.
How do I apply a percentage increase or decrease?
For an increase, multiply the starting value by 1 plus the percentage divided by 100. For a decrease, multiply by 1 minus the percentage divided by 100.
What is reverse percentage?
Reverse percentage recovers an original value from a final value after a known increase or decrease. It divides the final value by the multiplier that created it.
What is the difference between percentage change and percentage difference?
Percentage change uses a stated original value as the baseline and has direction. Percentage difference compares two peer values symmetrically using their average, so swapping the values does not change it.
What are percentage points?
Percentage points describe an absolute change between percentages. Moving from 40% to 44% is 4 percentage points, while the relative percentage increase is 10%.
Is this percentage calculator free online and does it require registration or login?
Yes. This calculator is free to use online and does not require registration or login.
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Choose a different mode above to calculate another value. No account or login is needed.