Find X% of Y, what percent one number is of another, old-to-new percentage change and symmetric percentage difference with clear steps. All math runs privately offline.
Part of our Calculators collection — Explore more Calculators tools · See also: BMI, Ideal Weight & Body Fat Calculator, Tip Calculator.
Quick answer: Percentage Calculator — Percent of, change & difference Free, no signup, runs in your browser. See below for the interactive tool, 4-step guide and FAQs.
Deep dives from the Tool4SaaS blog — tested workflows, print sizes and fixes.
Reviewed by the Tool4SaaS Editorial Team — In-house reviewers who build and test every tool locally for accuracy across current Chrome, Edge, Firefox, and Safari. Last updated: . See our authors, methodology or contact us.
It covers the everyday percent questions across three views. The Percent view finds X% of Y, works out what percent one number is of another and grows or shrinks a base; the Change view compares an old value to a new one; the Difference view measures the symmetric gap between two peers. For instance, 20% of 150 returns 30, 30 of 150 returns 20%, 150 to 180 returns 20% growth, and 60 versus 80 returns a 28.57% difference.
Percentage change needs an old-to-new order: it divides the gap by the old value, so 150 to 180 is +20% but 180 to 150 is −16.67%. Percentage difference has no direction and divides the gap by the average of the two values, so 60 versus 80 is 28.57% either way. Use change for trends over time and difference to compare two peers on equal footing.
Change = (new − old) ÷ old × 100, with a positive sign for a rise and a negative sign for a fall. From 50 to 75 the gap is 25 over 50, giving +50%; reversing it gives −33.33%. When the old value is zero the result is undefined, so the tool flags it rather than dividing by zero.
Because it uses the mean of the two values as the denominator instead of picking a side. The gap 20 between 60 and 80 divides by their average 70 and multiplies by 100, giving 28.57% whichever order you enter. That symmetry suits comparing lab replicates, peer prices or A/B results where neither value is the baseline.
No account, payment or connection is needed, and everything runs in your browser, so entries such as a 120-dollar jacket at 25% never leave the device and clear when the tab closes. Displayed figures round to two decimals, so a third becomes 33.33% on screen while the internal math keeps extra digits for chained steps.
A 120-dollar jacket at 25% off saves 30 and leaves 90 payable. An 18% tip on an 84.50-dollar bill adds 15.21, and 30 correct out of 150 is 20% complete. Each view shows the formula line beside the answer so you can confirm which base was used before trusting the number.
Three views centralize the common percent tasks in one offline page. The Percent view multiplies a rate by a base, divides a part by a whole and grows or shrinks a base; the Change view measures old-to-new movement; the Difference view compares two peers symmetrically. Shoppers take 25% off a 120-dollar jacket to save 30 and pay 90, diners add 18% on an 84.50-dollar bill for a 15.21 tip, students see 30 correct out of 150 as 20%, and analysts read 60 versus 80 as a 28.57% gap. Reference table: percent-of equals rate times base | what-percent equals part divided by whole times 100 | change equals new minus old divided by old times 100 | difference equals the absolute gap divided by the mean times 100.
The two comparison views answer different questions. Change is directional: 150 to 180 is +20% because the gap 30 divides by the old value 150, while the reverse divides by 180 for −16.67%. Difference is neutral: 60 versus 80 divides the gap 20 by the mean 70 for 28.57% either way. Edge case: a zero old value leaves change undefined and the tool flags it, whereas two zeros return 0% difference rather than an error. Limitation: both views use a single pair of values, so multi-step discounts and compounding need stepwise entry, and neither weights a value by reliability or volume. Percentage points differ from percent change too: moving a rate from 4% to 5% is one percentage point but a 25% relative rise.
Percent view: 25% of 120 is 30, so the jacket drops to 90; 30 of 150 returns 20% completion. Change view: 50 to 75 is a +50% rise, 75 to 50 a −33.33% fall. Difference view: 60 versus 80 is 28.57% and stays 28.57% when swapped. Limitation: figures display to two decimals, so repeating values round on screen even though the calculation keeps more precision. For a full markdown with tax see the discount calculator, and for tip splitting across a group see the tip calculator.