Verified by NIST Numerical Methods + BLS Economic Indicators
Input Parameters
Quick Formula
Base formula: `(part / whole) * 100`. Use change mode for growth or decline and difference mode for relative spread.
Calculation Result
Result
30.00%
Reference Table
Use Case
Formula
Example
Percent of value
(B * A) / 100
20% of 150 = 30
Reverse percent
(A / B) * 100
30 of 200 = 15%
Percent change
((B - A) / A) * 100
100 to 125 = 25%
Percentage Guide
Percentage calculations support pricing, discount analysis, growth tracking, and budgeting. For financial decisions, always separate percentage points from percentage change to avoid interpretation errors.
2026 Data Context
Category
Typical Range
Usage
Retail discount
5% to 40%
Price reduction
Inflation change
1% to 8%
Economic trend
Commission rate
2% to 20%
Sales payout
Validation Notes
Inputs accept decimals and negative values where mathematically valid. A zero denominator returns zero by design to prevent invalid division output.
Percentage FAQ
What is the basic formula for a percentage?
The word percentage comes from 'per centum', meaning 'per 100'. The basic formula is (Part / Whole) × 100. For example, if you have 20 apples out of 100, you have (20/100) × 100 = 20%.
How do I calculate percentage increase?
To find the percentage increase: ((New Value - Original Value) / Original Value) × 100. If a price goes from $100 to $120, the increase is (($120 - $100) / $100) × 100 = 20%.
How do I calculate percentage decrease?
To find the percentage decrease: ((Original Value - New Value) / Original Value) × 100. If a price drops from $100 to $80, the decrease is (($100 - $80) / $100) × 100 = 20%.
What is the difference between percentage and percentage points?
A percentage is a ratio, while percentage points refer to the arithmetic difference between two percentages. For example, if an interest rate rises from 5% to 6%, it has increased by 1 percentage point, which is a 20% relative increase.
How do you add a percentage to a number?
Multiply the original number by (1 + percentage/100). To add 15% to $100: $100 × (1 + 0.15) = $115.
How do you subtract a percentage from a number?
Multiply the original number by (1 - percentage/100). To take 20% off $100: $100 × (1 - 0.20) = $80.
How do I convert a fraction to a percentage?
Divide the numerator by the denominator and multiply by 100. For example, 3/4 becomes 0.75, then 0.75 × 100 = 75%.
How do I convert a decimal to a percentage?
Simply multiply the decimal by 100 and add the '%' sign. For example, 0.456 becomes 45.6%.
What is VAT and how is it calculated?
Value Added Tax (VAT) is a consumption tax. To find the VAT amount: (Net Price × VAT Rate) / 100. To find the total price: Net Price × (1 + VAT Rate/100).
How do I calculate CAGR (Compound Annual Growth Rate)?
CAGR is the geometric progression ratio that provides a constant rate of return: [(End Value / Start Value)^(1 / Number of Years)] - 1. Then multiply by 100 to get the percentage.
Why is 100% of something just the original amount?
100% means 100 per 100, which equals 1 (100/100 = 1). Multiplying any number by 1 leaves it unchanged.
What happens if a value increases by more than 100%?
A 100% increase means the value has doubled. A 200% increase means it has tripled (Original + 2 × Original). There is no upper limit to percentage increase.
Can a percentage be negative?
In mathematics, percentages usually refer to absolute ratios (0-100+). However, in financial contexts, a 'negative percentage' usually indicates a decrease or a loss.
How do I find the 'Whole' if I know the 'Part' and the 'Percentage'?
Use the formula: Whole = Part / (Percentage / 100). If 20 is 10% of a number, then Whole = 20 / 0.10 = 200.
What is percentage error?
It measures the inaccuracy of a measurement: (|Experimental Value - Theoretical Value| / |Theoretical Value|) × 100. It shows how close a result is to the target.