Percentage Calculator
Calculate percentages, percentage change, and percentage increase or decrease instantly.
What is X% of Y?
The percentage you want to take.
The base number.
Percentages show up everywhere else on Skycally too. If you are pricing a product, the Margin Calculator turns cost and revenue into margin and markup percentages. For a restaurant bill, the Tip Calculator applies a tip percentage and splits the total. When the numbers are in different currencies, run them through the Currency Converter first, and for weights, lengths or temperatures the Unit Converter gets everything onto the same scale before you compare.
How it works
Each tab uses one formula. A percentage is just a fraction out of 100, so every calculation below is either multiplying by a fraction or dividing to find one.
15% of 200 = 0.15 × 200 = 30
25 out of 200 = 25 ÷ 200 × 100 = 12.5%
80 → 100 = (20 ÷ 80) × 100 = 25% increase
250 increased by 20% = 250 × 1.20 = 300
How to use
- 1
Pick the tab that matches your question — X% of Y, X is what percent of Y, percentage change, or increase/decrease.
- 2
Type your two numbers into the fields. Results update instantly as you type.
- 3
Read the highlighted result, plus the formula used underneath it.
Percentage Calculator — Percentage Increase, Percentage Change & Percent of a Number
Free online percentage calculator with four modes: percentage of a number calculator, X is what percent of Y, percentage change calculator, and percentage increase or decrease calculator. Instant results, no signup.
Skycally's Percentage Calculator answers the four percentage questions people actually search for, each on its own tab. Use the percentage of a number calculator to find what 15% of 200 is, the reverse mode to find what percent 25 is of 200, the percentage change calculator to measure the difference between an old and a new value, and the percentage increase calculator to add or subtract a percentage from any number. Every result recalculates as you type — there is no calculate button and nothing to submit.
The percentage change tab is the one most people are looking for when they search for a percentage increase calculator. Enter the original value and the new value and the tool shows the change as a percentage, colour-coded green with an up arrow for an increase and red with a down arrow for a decrease, so you never have to work out the sign yourself. This is the calculation behind price rises, salary bumps, exam score improvements, weight loss, traffic growth and year-over-year revenue comparisons.
The increase and decrease tab works the other way round: you already know the percentage and want the resulting number. Toggle between increase and decrease and the tool multiplies your starting number by 1 plus or minus the percentage — useful for adding VAT or sales tax, applying a discount, marking up a wholesale price, or projecting next year's budget after a fixed percentage raise.
Everything runs in your browser using plain arithmetic. Nothing you type is uploaded, saved or logged, there is no signup, and the tool works the same on a phone as it does on a desktop. If you need related maths, the Margin Calculator handles pricing margins and markup, and the Tip Calculator handles bills and splitting.
Frequently Asked Questions
How do I calculate percentage increase?
Subtract the original value from the new value, divide by the original value, then multiply by 100. Going from 80 to 100: (100 − 80) ÷ 80 × 100 = 25% increase. Use the 'percentage change' tab and it does this for you, showing a green up arrow for an increase.
What is X percent of Y?
Divide the percentage by 100 and multiply by the number. 15% of 200 is 0.15 × 200 = 30. The first tab of the calculator does exactly this as you type.
How do I calculate what percent one number is of another?
Divide the part by the whole and multiply by 100. 25 out of 200 is 25 ÷ 200 × 100 = 12.5%. Use the 'X is what percent of Y' tab.
How do I calculate percentage decrease?
Use the same formula as percentage increase: ((new − original) ÷ original) × 100. A negative answer means a decrease. Going from 200 to 150: (150 − 200) ÷ 200 × 100 = −25%, shown as a 25% decrease with a red down arrow.
How do I add 20% to a number?
Multiply by 1.20. 250 increased by 20% is 250 × 1.20 = 300. Use the 'increase / decrease' tab with Increase selected — handy for adding tax or a markup.
How do I take 30% off a price?
Multiply by 0.70 (that is 1 − 30 ÷ 100). A $80 item with 30% off costs 80 × 0.70 = $56. Select Decrease on the 'increase / decrease' tab.
Why does the percentage change calculator need a non-zero original value?
Percentage change divides by the original value, and dividing by zero is undefined. If your starting value is 0 there is no meaningful percentage change — any increase from zero is mathematically infinite.
Is this percentage calculator free and private?
Yes. It is free with no signup, and all the maths runs locally in your browser. Nothing you enter is sent to a server, stored or logged.
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