Knowledge base
Learn percentages, one scenario at a time
A growing library of focused, search-intent guides covering every kind of percentage math you run into — paired with the calculator that does the arithmetic for you.
Quick start
Skip ahead to the math you need
Every guide here uses the same step-by-step format: explain the formula, show a worked example, compare values in a table, list common mistakes, and link back to the live calculator.
5 guides
Increase & decrease
Step-by-step pages for raising, lowering and comparing values by a percent.
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Percentage increase
How to calculate a 10% increase on any number
Learn how to calculate a 10% increase on a price, salary or balance. Step-by-step formula, worked examples, comparison tables and free percentage calculator.
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Percentage decrease
How to calculate a 25% decrease step by step
A 25% decrease cuts a number to three-quarters of itself. See the formula, a worked example, a comparison table and common mistakes to avoid.
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Percentage change
The percentage change formula, in plain English
Master the percentage change formula: ((new − old) ÷ old) × 100. Worked example, comparison table, mistakes and direct-to-calculator links.
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Salary math
Salary increase percentage calculator and guide
Calculate any salary raise as a percentage of your current pay. Step-by-step formula, comparison table, negotiation tips and instant calculator link.
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Pricing math
Price reduction percentages explained for shoppers and sellers
Understand how price reductions work as percentages on both sides of the till. Formula, examples, comparison table and free percent-off calculator.
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5 guides
Formula guides
Plain-English breakdowns of the percentage formulas you use most.
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Percentage basics
What is a percentage? A friendly introduction
A percentage is a way of expressing a number as a fraction of 100. Learn what percentages are, why they matter and how to use them with our free calculator.
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Percentage basics
How percentages work in everyday math
See how percentages turn fractions into clean comparisons. Read the formula, walk through worked examples and try the percentage calculator in one click.
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Formula reference
The percentage formula, explained without the jargon
The percentage formula in one line: (part ÷ whole) × 100. See the variations for increase, decrease and change, with worked examples and a calculator.
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Percent of a number
How to find a percentage of a number
Find any percent of any number with a single multiplication. Worked examples, mental-math shortcuts, common mistakes and a free percentage calculator.
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Ratio conversion
Ratio to percentage conversion guide
Convert any ratio into a percentage with a single formula. Read the steps, see real-world examples and use the free percentage calculator.
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5 guides
Discount, tax & tip
Real-world shopping, sales-tax and tipping math made simple.
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Percent off
How to calculate percent off any price
Calculate the sale price and the savings on any discount in seconds. Step-by-step percent-off formula, comparison table, mistakes and a free calculator.
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Sales tax
Sales tax percentage calculator and step-by-step guide
Add sales tax to any subtotal, or back tax out of a gross price. Formula, comparison table, common mistakes and a free percentage calculator.
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Restaurant tip
How to calculate a restaurant tip without slowing the table down
Calculate any restaurant tip in seconds using the 10% shortcut. Read the formula, see the comparison table, and skip awkward bill-time math.
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Discount math
The discount percentage formula explained
The discount percentage formula in one line. See the savings, the sale price and the comparison table, and try the free percentage calculator.
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Tax math
How to add tax to a price the right way
Add sales tax, VAT or GST to any price with confidence. Formula, worked example, comparison table and a free percentage calculator.
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5 guides
Business & finance
Margin, markup, commission, interest and growth percentages explained.
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Profit margin
How to calculate profit margin percentage
Calculate gross and net profit margin from any revenue and profit figures. Read the formula, see worked examples and try the free percentage calculator.
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Markup
How to calculate markup percentage on cost
Calculate markup percentage from cost and selling price. See the formula, compare markup vs margin, and use the free percentage calculator.
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Commission
Commission percentage explained for sales teams and freelancers
Calculate any commission as a percent of sales. Read the formula, tiered-rate example, common mistakes and try the free percentage calculator.
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Interest math
Interest rate percentage guide for borrowers and savers
Understand interest rates as percentages on loans and savings. Read the simple-interest formula, compare APR vs APY, and use the calculator.
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Business growth
Business growth percentage calculator and guide
Calculate revenue or user growth as a percent. Read the formula, see real-world examples and use the free percentage change calculator.
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5 guides
Grades & education
Convert marks, fractions and ratios into clean classroom percentages.
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Grades
How to calculate grade percentages from raw marks
Convert raw marks to a percentage grade in a single division. Step-by-step formula, conversion table, common mistakes and a free percentage calculator.
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Exam scores
Exam score percentage guide for students
Turn any exam score into a percent and a target grade. Read the formula, see the conversion table and try the free percentage calculator.
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Fractions to percent
How to convert fractions to percentages
Convert any fraction to a percent in two simple steps: divide, then multiply by 100. Worked examples, conversion table and free percentage calculator.
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Study guide
Percentage math for students: study guide and shortcuts
A student-friendly study guide to percentage math: formulas, shortcuts, comparison tables and a free calculator for instant practice.
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Math basics
How to find a percentage in math
Find any percentage in math with one formula: (part ÷ whole) × 100. See worked examples, conversion tables and the free percentage calculator.
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Found your topic? Try the math live.
Every guide on this page links to the same percentage calculator, configured for the exact mode you need: basic percent, increase, decrease, or percentage change.
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