Percentage Calculator
Calculate any percentage instantly — what is X% of Y, percentage change, percentage difference, and more.
What is Percentage Calculator?
Percentage calculations are among the most frequently performed calculations in business, finance, education, and daily life — yet they are surprisingly easy to confuse. The basic question "what is 15% of 80?" is straightforward (12), but percentage change ("sales increased from 80 to 96 — what percentage increase is that?"), percentage of total ("our department spent $12,000 of a $80,000 budget — what percentage is that?"), and percentage difference ("how much larger is 96 than 80 as a percentage?") require different formulas that are often mixed up. This calculator handles all standard percentage calculation types with clear labelling of which formula is being used, so you always know you're using the right calculation for your question.
How to Use Percentage Calculator
- 1
Select Calculation Type
Choose from: What is X% of Y? / X is what percent of Y? / What is the percentage change from X to Y? / Increase/decrease a number by a percentage.
- 2
Enter Your Numbers
Input the relevant values for your chosen calculation. The form adjusts to show only the fields needed for the selected calculation type.
- 3
Get the Result
Instantly see the result with the formula used displayed alongside — so you understand the calculation, not just the answer.
Use Cases
Business Reporting
Calculate percentage changes in sales, costs, and KPIs for monthly and quarterly reports. "Revenue grew from £142,000 to £168,000" — what's the percentage increase? (168,000 - 142,000) / 142,000 × 100 = 18.3% growth. Use this consistently across all metrics to make report figures accurate and comparable.
VAT and Tax Calculations
Calculate prices including or excluding VAT/sales tax: to add 20% VAT to a £50 price = £60; to find the ex-VAT price from a £60 VAT-inclusive price = £60 / 1.20 = £50. The reverse calculation (removing tax from an inclusive price) is where people most often use the wrong formula.
Academic and Test Scores
Calculate percentage scores from raw marks (28/35 = 80%), minimum marks needed to achieve a grade threshold (need 70% of 35 = 24.5 marks), or percentage improvement between test attempts.
Features
Six Calculation Types
Covers all common percentage calculations: percentage of a number, number from percentage, percentage change, percentage increase/decrease, percentage difference, and what percentage one number is of another.
Formula Display
Shows the mathematical formula used alongside the result — essential for understanding which percentage calculation is appropriate and for replicating it in spreadsheets.
Reverse Calculation
Given a final number and the percentage applied, calculates the original value — useful for working backwards from a discounted price, tax-inclusive total, or percentage-adjusted figure.
Percentage to Fraction/Decimal
Converts between percentage, decimal, and fraction representations — helpful for academic work, programming, and financial modelling.
Frequently Asked Questions
Percentage Change = ((New Value - Old Value) / Old Value) × 100. A positive result is an increase; negative is a decrease. Example: sales went from 200 to 250. Change = ((250-200)/200) × 100 = 25% increase. Common mistake: using the new value as the denominator instead of the old value. The old (original) value is always the base for percentage change calculations.
Percentage change has a clear direction (from old to new) and uses the original value as the base. Percentage difference is symmetric — it measures how different two values are without implying which came first. Formula: |V1-V2| / ((V1+V2)/2) × 100. Use percentage change for before/after comparisons (revenue growth, price changes). Use percentage difference when comparing two equivalent things (price at two retailers, two products' sizes).
To increase a number by a percentage: New Value = Original × (1 + Percentage/100). Example: £200 + 15% = 200 × 1.15 = £230. To decrease: New Value = Original × (1 - Percentage/100). Example: £200 - 15% = 200 × 0.85 = £170. Common mistake: adding the percentage to the original instead of multiplying: £200 + 15 = £215 is wrong. The correct answer is £230 because 15% of 200 is 30, not 15.
To find the original value before a percentage increase was applied: Original = New Value / (1 + Percentage/100). Example: a price is £115 after a 15% increase. Original = 115 / 1.15 = £100. The most common error is subtracting the percentage from the new value: £115 - 15% = £97.75 — this is wrong because it calculates 15% of the increased value, not 15% of the original.
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