Multiply the value by the percentage and divide by 100. Example: 20% of 150 = (20 ÷ 100) × 150 = 30. In the "% of a value" mode, just enter 20 and 150.
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Percentage of a value, percent change, increase and discount with steps.
A percentage expresses a number as a fraction of 100, so 20% means 20 per 100, or 0.20. This calculator gathers the six everyday percentage tasks in one place: finding P% of a value (V·P/100), working out what percent X is of Y (X/Y·100), the percent change from an initial to a final value ((B−A)/|A|·100), increasing a value by P% (V·(1+P/100)), applying a P% discount (V·(1−P/100)), and recovering the original value before a P% increase (final ÷ (1+P/100)). Each mode prints the formula with the numbers substituted, step by step, so you follow the reasoning instead of just copying a number. Calculations use 64-bit floating point and display up to six decimals, trimming unnecessary zeros. It is built for the questions people actually type: tips, taxes, sale prices, grade weights, and salary raises.
Each mode applies a direct formula. 'P% of a value' is V·P/100; 'X is what % of Y' is X/Y·100; percent change is (B−A)/|A|·100; increasing by P% multiplies by (1+P/100); discounting P% multiplies by (1−P/100); and the original value before an increase is final ÷ (1+P/100).
It all comes down to two ideas: turn 'percent' into a fraction by dividing by 100, and choose between multiplying (to apply) or dividing (to reverse). The tool shows the numeric substitution at each step to keep the method transparent.
Example 1, % of a value: what is 15% of 80? (15 ÷ 100) · 80 = 0.15 · 80 = 12.
Example 2, original value: a jacket costs $90 after a 20% markup. The price before the increase was 90 ÷ (1 + 20/100) = 90 ÷ 1.20 = $75. Note that dividing by 1.20 is not the same as taking 20% off 90 (which would give 72).
A percentage point is not the same as a percentage: a rate rising from 10% to 12% went up 2 percentage points, but 20% in relative terms. And increases and discounts do not cancel out: a 50% discount followed by a 50% increase gives 0.5 · 1.5 = 0.75 of the original value, that is, 25% less.
In practice, percentages appear in discounts and interest, taxes and tips, price and audience changes, exam weights, and sales targets. The order in which you apply a discount and a tax can change the final total.
Paste the code into your HTML and the tool shows up on your page, without J-Kit's navigation and ads. It still runs in the browser of whoever visits your site.
<iframe
src="https://jkit.tools/embed/en-US/percentage-calculator"
width="100%"
height="600"
style="border:0"
loading="lazy"
title="Percentage Calculator"
></iframe>These references help contextualize formulas, standards, APIs and limitations used on this page. They do not replace professional validation when a result has legal, financial, medical or operational impact.
Multiply the value by the percentage and divide by 100. Example: 20% of 150 = (20 ÷ 100) × 150 = 30. In the "% of a value" mode, just enter 20 and 150.
What is P% of a value?
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