📊 Percentage Calculator

Use this percentage calculator to quickly answer questions like “What is X% of Y?”, “X is what percent of Y?”, and “What is the percent increase or decrease from one number to another?”. It’s useful for sales, discounts, grades, business metrics, and everyday math.

Percentage calculator results

Select a calculation type, enter your numbers, and choose Calculate Percentage Result to see the answer along with a plain-language explanation.

Percentage calculation breakdown

After you run a calculation, this section will show the inputs and the resulting percentage in a simple table so you can double-check your work or copy the numbers into a report.

Percentage calculator inputs and key terms

This calculator supports three common percentage questions. Here’s what each input means and when to use it.

• Calculation type: Choose whether you want to find what X% of Y is, what percent one number is of another, or the percent increase/decrease between two values.
• Percent (X): The percentage you want to apply to a base value, such as a tax rate, discount, tip, or commission (for example 15%, 20%, or 7.5%).
• Base value (Y): The starting amount to which the percentage is applied. For example, the price before discount, the original score, or the original quantity.
• Part value (X): The portion or subset you are comparing to a total. For example, the number of correct answers, the number of items sold, or the amount spent.
• Whole value (Y): The total or full amount used as the reference when you ask “X is what percent of Y?”. For example, total questions, total budget, or total capacity.
• Starting value (X): The original number before a change, such as last month’s sales, yesterday’s price, or an earlier balance.
• Ending value (Y): The new number after the change, such as current sales, today’s price, or your updated balance.
• Percent increase/decrease: Shows how much a value has gone up or down relative to its original value. This is popular in finance, business metrics, grades, and performance tracking.

Formulas used in the Percentage Calculator

The same core percentage ideas appear in many everyday situations. These are the formulas this calculator uses behind the scenes.

1. What is X% of Y?

Let X be the percentage and Y be the base value. First convert the percentage to a decimal, then multiply:
Result = (X ÷ 100) × Y
Example: 20% of 50 = (20 ÷ 100) × 50 = 10.

2. X is what percent of Y?

Let X be the part value and Y be the whole value. Divide the part by the whole and convert to a percentage:
Percent = (X ÷ Y) × 100%
Example: 25 is what percent of 80? (25 ÷ 80) × 100% = 31.25%.

3. Percent change from X to Y

Let X be the starting value and Y be the ending value. First find the difference, then divide by the starting value:
Change = Y − X
Percent change = (Change ÷ X) × 100%
If the result is positive, it is a percent increase. If it is negative, it is a percent decrease.

Note: Percent change is undefined if the starting value is 0 because you cannot divide by zero. In those cases, it may be better to describe the change in absolute terms instead of as a percentage.

Percentage Calculator FAQs

• What is the difference between “X% of Y” and “X is what percent of Y”?
  “X% of Y” means you are taking a fraction of a base value, such as 20% of 80. “X is what percent of Y” compares one value to another and asks what fraction it represents—like 16 is what percent of 80. The direction of the comparison matters and produces different results.
• How do I know if a percent change is an increase or a decrease?
  If the ending value is larger than the starting value, the percent change is positive and represents an increase. If the ending value is smaller, the percent change is negative and represents a decrease. This calculator shows the direction and the percent size of the change.
• Why does percent change behave strangely when the starting value is close to zero?
  Percent change divides by the starting value. When the starting value is very small, even tiny absolute changes become extremely large percentages, and if the starting value is exactly zero, the percent change is undefined. In these cases, it can be clearer to talk about the absolute change instead of the percent change.
• How can I use this calculator for discounts and sales tax?
  For discounts, use “What is X% of Y?” to find the discount amount, then subtract it from the original price. You can also use the same pattern to calculate sales tax by applying the tax rate to the pre-tax price and adding the result to get the final price.
• Can I use this calculator for grades and test scores?
  Yes. Use “X is what percent of Y?” where X is the number of points you earned and Y is the total possible points. The result tells you your percentage score. You can also use percent change to track how your grades improve over time.
• How precise are the results, and can I round them?
  The calculator uses standard floating-point arithmetic and formats most results to two decimal places, which is usually enough for everyday use. You can round further if needed for reports, invoices, or presentations, as long as you are consistent with your rounding rules.