CalcBloom
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Percentage calculator

Three quick percentage tools in one place. Type your numbers — the answer updates instantly.

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Guide

How to calculate percentages

A percentage is just a number out of 100. The word "percent" literally means "per hundred", so 20% is the same as 20 out of 100, or the fraction 20/100 = 0.2. Most everyday percentage questions fall into the three types on this page.

Percent of a number

To find a percent of a number, multiply the number by the percent and divide by 100. For example, 20% of 150 is 150 × 20 ÷ 100 = 30. This is handy for tips, taxes and discounts.

What percent one number is of another

Divide the part by the whole and multiply by 100. If you scored 30 out of 150, that is 30 ÷ 150 × 100 = 20%.

Percentage increase and decrease

Take the difference between the new and old values, divide by the old value, then multiply by 100. A price rising from 80 to 100 is a (100 − 80) ÷ 80 × 100 = 25% increase; falling from 100 to 80 is a 20% decrease.

Everyday examples

Common uses: a 15% tip on a $40 bill is 40 × 0.15 = $6. A 30%-off sale on a $50 item saves $15, so you pay $35. If 45 of 60 students passed, that is 45 ÷ 60 × 100 = 75%. Sales tax of 10% on $200 adds $20 for a $220 total.

Percentage formulas

Percent of a number: result = number × percent ÷ 100
What percent A is of B: percent = A ÷ B × 100
Increase or decrease: percent = (new − old) ÷ old × 100

How this calculator works

CalcBloom applies these standard arithmetic formulas directly in your browser using full floating-point precision, and rounds only for display. There are no external rates or data, so the result matches what you would get by hand or in a spreadsheet. Nothing you type is sent to a server.

Last reviewed: 2026-07

📖 Related guide: Percentages made easy: discounts, tips and tax

FAQ

Frequently asked questions

How do I calculate a percentage of a number?

Multiply the number by the percentage and divide by 100. For example, 20% of 150 is 150 × 20 ÷ 100 = 30.

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 ÷ 150 × 100 = 20% of 150.

How do I calculate percentage increase or decrease?

Subtract the old value from the new value, divide by the old value, and multiply by 100. A rise from 80 to 100 is a 25% increase.

Is this percentage calculator free and private?

Yes. It is completely free, and every calculation runs in your browser — the numbers you enter are never uploaded or stored.

How do I add or subtract a percentage from a price?

To add, multiply by (1 + percent/100): 200 plus 10% is 200 × 1.1 = 220. To subtract, multiply by (1 − percent/100): 200 minus 10% is 200 × 0.9 = 180.

What is the percentage difference between two numbers?

Divide the change by the original value and multiply by 100. From 80 to 100 the change is 20, so 20 ÷ 80 × 100 = 25%. Going from 100 to 80 is a 20% decrease, because the original value (100) is larger.

How do I turn a fraction or decimal into a percent?

Multiply a decimal by 100 (0.2 → 20%). For a fraction, divide the top by the bottom first, then multiply by 100 (3/4 → 0.75 → 75%).

What is the difference between percent and percentage points?

Going from 10% to 15% is a rise of 5 percentage points, but a 50% increase relative to the original 10%. Percentage points compare the two rates directly; percent compares the change to the starting value.