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Everyday Calculators

Percentage Calculator

Use this percentage calculator for common percent math: find a percent of a number, calculate percentage change, or work out what percent one value is of another.

Reviewed May 25, 2026EstimateFormula shown

Live calculator

Percentage calculator

20% of 15030

Use this for discounts, taxes, tips, and quick percent math.

45 is what percent of 6075.00%

Use this when comparing a part against a total.

Percentage change25.00% increase

Use this for price changes, growth, decline, and before/after comparisons.

Formula

Percentage formulas

X% of Y = (X / 100) x Y; percentage change = ((new - old) / old) x 100

Use the first formula to find a percent of a number. Use percentage change to compare an old value with a new value.

How to use

Steps

  1. Use the first row to find a percentage of a number.
  2. Use the second row to find what percent one number is of another.
  3. Use the third row to calculate percentage increase or decrease.
  4. Compare the results in the right column and copy the one that matches your question.

Example

Sample calculation

20% of 15030
45 out of 6075%
80 to 10025% increase

Calculator use

Best for

  • Quick percent result from percent, base number and part.
  • Quick everyday math with the result and formula in one place.
  • Shopping, date, time, unit, school, or household comparisons.
  • A fast check before moving the numbers into a spreadsheet.

Before relying on it

Check first

  • Entering percent, base number and part from different time periods or scenarios.
  • Mixing units, dates, or original values across the same calculation.
  • Rounding early and then using the rounded number in another step.
  • Copying a result without checking whether the inputs match the real-world question.

Benchmarks

How to read the result

The calculator is a decision aid, not a fixed rule. Use the output to compare scenarios and document your assumptions.

0% - 10%Small change

Often useful for discounts, tax, tips, price moves, and small metric changes.

10% - 25%Moderate change

Large enough that most people will notice it in a bill, budget, or report.

25%+Large change

Usually worth double-checking the original numbers and assumptions.

Calculator accuracy

Methodology and assumptions

The formula, inputs, example, and limitations are shown so the result is checkable, not just a number in a box.

Formula

X% of Y = (X / 100) x Y; percentage change = ((new - old) / old) x 100

Inputs used

Percent, Base number, Part, Whole, Original value, New value

Limitations

Results are estimates for quick planning and should be checked before important financial, legal, tax, health, or business decisions.

Last reviewed

May 25, 2026

Cite this page

Toolkit Shelf. Percentage Calculator. Retrieved May 25, 2026, from https://toolkitshelf.com/tools/percentage-calculator

FAQ

Common questions

How do I calculate a percentage of a number?

Divide the percentage by 100, then multiply by the number. For example, 20% of 150 is 0.20 x 150 = 30.

How do I calculate percentage increase?

Subtract the old value from the new value, divide by the old value, then multiply by 100.

What does percentage decrease mean?

Percentage decrease shows how much a value went down compared with the original value.