Percentage Calculator

Solve percent-of, percent-change, increase, decrease, and reverse-percentage questions with the base value clearly identified.

Drag & drop or upload an image or PDF

Enter a percent question, such as what is 18% of 250?

State which value is the part, whole, original, or new amount. You can include % and currency symbols.

Try an example

The base value decides the percentage

A percentage is a ratio measured per hundred. The same three quantities appear in most basic questions: the part, the whole, and the percent rate.

Change questions require extra care because the original amount is the comparison base. A rise from 80 to 100 is measured against 80, while a drop from 100 to 80 is measured against 100. Reverse percentages undo the multiplier that produced the final amount.

How to use the percentage calculator

Enter the problem as written

Type or paste the full expression. You can also upload a clear photo or PDF and check the extracted text before solving.

Read the working, not only the answer

Each transformation is separated and explained so you can compare it with your own method.

Ask about any step

Continue in the same solution to request another method, check a restriction, or ask why a rule applies.

Core percentage relationship

Use the known part, whole, and rate to solve for the missing quantity.

part = \frac{p}{100} \cdot whole, p = 100 \cdot \frac{part}{whole}

A reliable way to work through it

Name the quantities

Decide which number is the part, which is the whole or original amount, and which rate is given.

Convert the rate

Divide a percentage by 100 before multiplying, or multiply a decimal ratio by 100 to report a percent.

Use the correct change multiplier

Multiply by 1 + p/100 for an increase and 1 - p/100 for a decrease. Divide by that multiplier to recover the original.

Worked example

What percent of 240 is 54?

part = 54, whole = 240

Identify the compared amount and the full base amount.

p = 100 \cdot \frac{54}{240}

Divide the part by the whole and convert the ratio to a percent.

\frac{54}{240} = 0.225

The decimal ratio is exact.

p = 22.5%

Multiply the decimal by 100 and attach the percent sign.

54 is 22.5 percent of 240.

Common mistakes to check

Dividing by the new value

Percent change normally uses the original value in the denominator, not the final value.

Using 18 instead of 0.18

A percent must be divided by 100 before it is used as a multiplication rate.

Reversing a discount by adding it back

To undo a 20 percent discount, divide the final value by 0.80. Adding 20 percent to the discounted value uses a different base.

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Questions students ask

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

Divide the part by the whole, then multiply the ratio by 100 percent.

Can it calculate percentage increase and decrease?

Yes. Provide the original and new values so the change can be divided by the original amount.

What is a reverse percentage?

It recovers the original amount from a final amount and a known increase or decrease rate by undoing the change multiplier.

Is percent change from zero defined?

No. Relative percent change divides by the original value, so an original value of zero makes that calculation undefined.