Percentage Calculator
Last updated: May 2026
Solve the three most common percentage problems in one place: find a percent of a number, reverse the calculation, or measure percentage change.
Percentage summary
Your Percentage Result
X% of Y
What does this tool do and when should you use it?
The Percentage Calculator is a multi-purpose tool that handles the three most common percentage questions people encounter in daily life. Percentages show up everywhere — calculating a restaurant tip, figuring out how much tax is on an item, checking your test score, or measuring how much a price has changed. This tool covers all three core calculation types in a single, easy-to-use interface.
A lot of people get tangled up trying to remember whether to multiply, divide, or shift a decimal point when dealing with percentages. This calculator removes all of that uncertainty. It offers three clearly labelled modes: finding a percentage of a number (X% of Y), finding what percentage one number is of another (X is what % of Y), and calculating the percentage increase or decrease between two values. It is equally useful for students, professionals, shoppers, and anyone who wants a quick and accurate answer.
How to Use (Step-by-Step)
- Select Mode: Choose the type of calculation you need using the tabs at the top — "X% of Y", "X is what % of Y", or "% change".
- Enter Your Values: Fill in the two number fields based on the mode you have selected. The calculator handles decimals without any issues.
- Calculate: Click the calculate button to get your answer.
- View Result: The answer appears immediately below the form, along with a clear label showing the relationship between the numbers you entered.
Formula & Methodology
The formula used depends on which mode you have selected:
- Mode 1 (X% of Y): Formula:
(X ÷ 100) × Y. This converts the percentage to a decimal and multiplies it by the total value. - Mode 2 (X is what % of Y): Formula:
(X ÷ Y) × 100. This expresses one number as a fraction of another and converts it into a percentage. - Mode 3 (% Change): Formula:
((New Value − Old Value) ÷ Old Value) × 100. A positive result indicates an increase; a negative result indicates a decrease.
Worked Examples
Example 1: Calculating a Tip (Mode 1)
You want to leave a 15% tip on a $40 dinner bill. Mode 1 setup: What is 15% of 40? Calculation: (15 ÷ 100) × 40 = $6.00 tip.
Example 2: Finding Your Test Score (Mode 2)
You scored 45 points out of a possible 60 on an exam. Mode 2 setup: 45 is what % of 60? Calculation: (45 ÷ 60) × 100 = 75%. You got a 75%.
Example 3: Measuring a Rent Increase (Mode 3)
Your rent was $1,200 last year and is now $1,350. Mode 3 setup: Change from $1,200 to $1,350. Calculation: ((1,350 − 1,200) ÷ 1,200) × 100 = 12.5% increase.
FAQ
What does "percent" actually mean?
"Percent" literally means "per one hundred." It is a way of expressing a number as a fraction of 100. So 50% means 50 out of every 100, which is the same as one-half.
Can I use this to calculate sales tax?
Yes — use Mode 1. If your tax rate is 8% and the item costs $50, calculate 8% of 50 to get the tax amount ($4.00). Add that to the original price to find the total cost ($54.00).
Can a percentage be higher than 100%?
Yes. While you cannot give more than 100% effort in a physical sense, mathematically a 200% increase means something has tripled in value — it had its original 100% and then grew by 200% more on top of that.
Why is percentage change useful?
Percentage change gives context that raw numbers alone cannot. A $5 price increase on a $10 item is enormous (50% up), but the same $5 increase on a $1,000 item is barely noticeable (0.5% up). Percentage change makes comparisons meaningful.
What is the quickest way to find 10% of any number in my head?
Just move the decimal point one position to the left. For example, 10% of 450 is 45. Ten percent of 1,200 is 120. Once you have 10%, you can build up to any other percentage quickly from there.