Percentage Calculator Ireland
Calculate percentage of a number, percentage change, difference, reverse percentages, discounts and marks with instant formula-based answers.
Percentage Inputs
Example: if 30 is 15% of a number, this mode finds the whole number.
Percentage Result
Choose a percentage mode and enter your numbers to see the result, formula and breakdown.
About This Percentage Calculator
Use this calculator for everyday percentage questions: percentage of a number, one number as a percentage of another, reverse percentages, percentage increase or decrease, percentage difference, discounts, salary raises and exam marks.
One calculator, multiple percentage jobs. The tabs keep common calculations in one place so the page can answer several search intents without creating separate shortcodes.
Formula-first results. Each result shows the answer plus the formula used, so users can understand the calculation rather than only copying a number.
This is a general maths calculator. For Irish tax, salary, VAT or mortgage estimates, use the related calculators below.
How This Calculator Works
Who This Calculator Is For
Percentage formula examples
Most percentage questions come down to choosing the correct base number. Match your question to the formula and calculator tab below.
| Your question | Formula | Calculator tab |
|---|---|---|
| What is P% of N? | (P ÷ 100) × N | What is % of? |
| X is what % of Y? | (X ÷ Y) × 100 | X is what %? |
| X is P% of what number? | X ÷ (P ÷ 100) | X is % of what? |
| How much did a value change? | ((new − old) ÷ old) × 100 | Change / Difference |
| Add or remove P% | N × (1 ± P ÷ 100) | Add / Remove % |
| What percentage are my marks? | (scored ÷ total) × 100 | Marks % |
Quick examples: 20% of 150 is 30; 45 as a percentage of 180 is 25%; and if 30 is 15% of a number, the whole number is 200.
Reverse percentage: find the whole number
Use a reverse percentage when you know the part and its percentage but need the original whole number.
Suppose 30 is 15% of an unknown number. Convert 15% to 0.15, then divide: 30 ÷ 0.15 = 200. You can do this directly in the X is % of what? tab.
This is different from finding an original price before a discount or increase, because those calculations use the percentage that remains after the change. Always identify what the stated percentage represents before choosing the formula.
Percentage change vs percentage difference
Percentage change and percentage difference are often confused, but they answer different questions.
Percentage change is best when there is a clear old value and new value, such as a price changing from €100 to €125. The formula is (new − old) ÷ old × 100, so the increase is 25%.
Percentage difference is better when you are comparing two values without treating one as the starting point. It uses the average of the two values as the base, so the result is symmetric whichever value you put first.
Percentage of marks calculator
Marks percentage is one of the simplest percentage calculations.
To find a marks percentage, divide marks scored by total marks and multiply by 100. If you scored 250 out of 350, the calculation is 250 ÷ 350 × 100 = 71.43%.
This can be used for exam scores, assignments, tests, quizzes and total marks across multiple papers. If different exams have different weightings, calculate the weighted score separately before converting to a final percentage.
Discounts, salary raises and money percentages
Percentages are useful for discounts, price increases, tax-style estimates and salary raises.
For discounts, use the decrease mode: a 15% discount on €80 means €80 × 0.85 = €68. For price increases or salary raises, use the increase mode: a 5% increase on €40,000 means €40,000 × 1.05 = €42,000.
For Irish payroll take-home pay after a salary increase, use the Net Salary Calculator because PAYE, USC and PRSI can change the amount you actually receive.