BYTETOOLS

Percentage Calculator

Calculate what X% of a number is, what percent one number is of another, and percentage increase or decrease between two values — instantly and free.

50
25% of 200

How it was calculated

25 ÷ 100 × 200 = 50

What is the Percentage Calculator?

The ByteTools Percentage Calculator solves the three percentage problems people ask most: what is X% of Y, X is what percent of Y, and the percentage change from one value to another.

  • Three modes: percent of a number, reverse percentage, and percentage change
  • Live results as you type — no calculate button needed
  • Shows the formula used so you can verify the math
  • Handles decimals and negative values correctly
  • 100% private — calculations never leave your browser
  • Free, no sign-up, works offline

How to use the Percentage Calculator

  1. 1

    Choose a mode: “What is X% of Y”, “X is what % of Y”, or “% change from X to Y”.

  2. 2

    Enter your two numbers in the input fields.

  3. 3

    Read the live result and the worked formula shown below the inputs.

  4. 4

    Switch modes at any time — your numbers stay in place so you can compare answers.

About the Percentage Calculator

The ByteTools Percentage Calculator solves the three percentage problems people ask most: what is X% of Y, X is what percent of Y, and the percentage change from one value to another. Pick a mode, type your numbers, and the answer updates live — no formulas to remember and no rounding mistakes.

It is built for students checking homework, shoppers working out tips and discounts, analysts computing growth rates, and anyone splitting bills or comparing prices. Each mode shows the underlying calculation, so you can see exactly how the result was reached.

Everything is computed locally in your browser with JavaScript — nothing you type is uploaded or stored, and the calculator works offline once the page has loaded.

Frequently asked questions

How do I calculate the percentage of a number?

Multiply the number by the percentage and divide by 100. For example, 15% of 80 is 80 × 15 ÷ 100 = 12. The “What is X% of Y” mode does this for you automatically.

How do I find what percent one number is of another?

Divide the first number by the second and multiply by 100. For example, 30 is 30 ÷ 120 × 100 = 25% of 120. Use the “X is what % of Y” mode and the tool shows the division for you.

How is percentage increase or decrease calculated?

Percentage change is (new − old) ÷ old × 100. Going from 50 to 65 is (65 − 50) ÷ 50 × 100 = +30%. A negative result means a decrease — the tool labels increase and decrease clearly.

What is the difference between percentage change and percentage points?

Percentage points measure the simple difference between two percentages, while percentage change is relative. Going from 10% to 15% is a rise of 5 percentage points, but a 50% relative increase.

Can this calculator handle negative numbers?

Yes. All three modes accept negative and decimal inputs. For percentage change with a negative starting value the sign convention can be counter-intuitive, so the tool shows the raw formula so you can interpret the result.

Guides for Percentage Calculator

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