Percentage Calculator

How do you choose the right percentage calculation?

To find a percentage of an amount, select X% of Y, enter the rate in Percentage (%) and the amount in Value. For 15% of 240, the steps are 15 ÷ 100 = 0.15, then 0.15 × 240 = 36. Results appear as you type. The other tabs answer different questions, so decide which number is the whole or starting reference before entering values.

Your question	Mode	Example result
What is 15% of 240?	X% of Y	36
36 is what percent of 240?	X is ?% of Y	15%
How much did 240 grow to 276?	% Change	15%
How far apart are 40 and 60?	% Difference	40%
36 is 15% of what?	X is Y% of ?	240
What is 240 increased by 15%?	Add/Subtract %	276
What does +15% then −10% do?	Successive %	3.5% net increase

What do percentages and part-to-whole ratios mean?

A percentage expresses a ratio per hundred. To find X% of Y, use (X / 100) × Y. For a mental check, 10% means one tenth and 1% means one hundredth. Combine these parts: 15% is 10% plus half of 10%. A rate above 100% is valid arithmetic and produces more than the original amount when that amount is positive.

To find the rate instead, use (part / whole) × 100. A score of 68 out of 80 is 85%. Enter 68 in Part value and 80 in Whole value. The denominator must describe the full quantity, using the same units as the part. Three people out of twelve is 25%; dividing by the nine remaining people answers a different question. A whole of zero is undefined.

How does percentage change handle direction and negative values?

The % Change tab uses ((to − from) / |from|) × 100. Enter the original in From value and the later amount in To value. The absolute-value denominator is this calculator's convention for negative starting values: moving from −40 to −60 gives −50%, while −40 to −20 gives +50%. Interpret those results alongside the original amounts, especially when crossing zero.

Change is directional. Moving from 100 to 50 is −50%, but recovering from 50 to 100 requires +100%. A starting value of zero produces an undefined result, even when the later value is also zero. There is no nonzero starting denominator from which to calculate a relative change.

When should you use percentage difference instead?

Select % Difference to compare two values without choosing a baseline. It uses |A − B| / ((|A| + |B|) / 2) × 100. For 40 and 60, the absolute gap is 20 and the average magnitude is 50, so the difference is 40%. Swapping the inputs leaves the answer unchanged.

This compares measurements in the same units; it does not normalize different scoring scales. The absolute-value denominator also defines behavior for negative values. For −40 and −60 the difference is 40%; for −40 and 60 it is 200%. When both inputs are zero, the calculator returns 0% by convention.

How do you recover a whole or an original price?

For a known part, use X is Y% of ? and whole = known value / (percentage / 100). If a 20% discount saved 30, the original price was 150. Enter the saving as Known value and 20 as Percentage (%). Do not enter the sale price as the saving: those represent different fractions of the original.

For a final price, use Add/Subtract %. The forward multiplier is 1 + p/100 for Increase (+) and 1 − p/100 for Decrease (−). Select Find the original from the result to divide by that multiplier. A final amount of 120 after a 20% increase means 120 ÷ 1.2 = 100. A final amount of 80 after a 20% decrease means 80 ÷ 0.8 = 100.

Reversing a 100% decrease leaves no result because the multiplier is zero. The tool performs arithmetic using your rate; it does not determine applicable tax rates or invoice rules. Use the Invoice VAT Calculator for its dedicated VAT workflow.

Why do successive changes multiply rather than add?

Each change applies to the amount left by the previous change. Starting with 200, a 20% discount leaves 160; a further 10% discount leaves 144. The combined factor is 0.8 × 0.9 = 0.72, a 28% reduction. Likewise, +50% then −50% leaves 75% of the start, rather than returning to it.

In Successive %, fill every change row with a signed rate. Use Add change or Remove to keep between two and ten rows. Without a starting amount, the result is the net percentage; with Start value (optional), the steps include running amounts. For repeated growth over time, see the Compound Interest Calculator.

How are percentage points different from percent change?

A rate moving from 4% to 5% rises by one percentage point, but its relative increase is 25%. Enter 4 and 5 in % Change and select Values are percentages to show both. Enter rates as percentage numbers, not decimal fractions. The checkbox appears only when the starting value is nonzero, so this interface does not show a points-only result for a zero starting rate.

What should you check before copying or saving a result?

Choose the number format first: 1,234.56, 1.234,56, or 1 234,56. The initial choice follows your browser language. Grouped digits must use valid three-digit groups, and scientific notation is not accepted. Changing the format clears inputs and history to prevent reinterpreting existing values.

JavaScript number arithmetic uses IEEE 754 floating-point values, so decimal calculations can involve rounding. Display precision depends on magnitude: at most two decimal places for absolute values of 1,000 or more, four from 1 to below 1,000, and six below 1. Copying takes the displayed result, not hidden precision. Very large nonfinite outputs display a dash. This is not an exact decimal accounting engine.

Calculations run locally, and history lives in page memory rather than persistent storage. History keeps up to ten entries; selecting one restores its mode and inputs. Clear all, reloading, or changing number format clears that history. Treat it as a temporary comparison aid, not a saved record.