Percentage Calculator
Answer the three most common percentage questions. Your work stays on this device whenever possible.
How to use Percentage Calculator
- Open the Percentage calculation selector and pick one of seven modes, such as "What is X% of Y?" or "Percentage change from X to Y".
- Type the first figure in X and the second in Y; the meaning of each depends on the mode you chose.
- Press "Calculate" and read the answer together with its printed formula line.
- For pricing work, switch to "Cost X with Y% markup & margin" to see selling price, gross profit and margin side by side.
- Swap X and Y and recalculate if you want to check which base the percentage is measured against.
Worked example
Pick "Cost X with Y% markup & margin", enter X = 40 and Y = 25. Markup amount = 40 × 0.25 = 10.00, so Selling Price = 50.00 and Gross Profit = 10.00. Gross Margin = 10 ÷ 50 = 20.00%, while the markup on cost stays 25%. The two percentages differ because they use different bases.
When to use this tool
- Setting a shelf price that reaches a chosen markup while seeing the resulting margin.
- Finding how much a monthly bill rose in percentage terms between two invoices.
- Working back from a total to the base figure when only the percentage share is known.
Important limitations
Percentages express relative proportions, not compounding interest or tax brackets. Always verify whether a formula requires percentage of, percentage increase, or percentage difference.
Frequently asked questions
What is the difference between markup and margin?
Markup is profit as a share of cost; margin is profit as a share of the selling price. A 25% markup on a cost of 40 gives a 50 selling price, but the gross margin is only 20%. The mode prints both.
Why can't X be zero in the change mode?
Percentage change divides by the starting value, so a start of zero is undefined and the tool shows an error. The calculation also uses the absolute value of X, so changes from negative numbers keep a sensible sign.
Does the order of X and Y matter?
Yes, for most modes. Going from 50 to 75 is +50%, but going from 75 to 50 is about −33.33%. In "X is what % of Y", swapping the values gives a different, reciprocal answer.
How many decimals are shown?
The rate and change modes show two decimals, while the "of" and reverse modes show up to six. Repeating decimals such as one third are therefore trimmed, and you should round further for reports.
How do I find the original value before a percentage?
Use "X is Y% of what?". It divides X by Y ÷ 100, so knowing that 30 is 12% of a total returns 250. This reverses a percentage without needing algebra.