Blog

Practical how-to posts with worked examples. Each one links to the matching free tool so you can check your own numbers.

Learn the reverse percentage method to find the original price when you only know the sale price and the discount.

Step-by-step formula for percentage change, why going up 30% and down 30% do not cancel out, and worked examples.

Calculate gross profit, margin and markup with clear examples, and learn why a 40% margin is not a 40% markup.

Work out the lowest price you can charge after fees and costs, and the price needed to earn a target profit.

Add VAT to a net price or take it out of a gross price correctly, with a simple method that avoids the common 5% mistake.

Exact formulas and a quick mental trick for converting Celsius and Fahrenheit, with common reference temperatures.

Convert height in centimetres to feet and inches in three steps, with examples and a reference table.

Why two discounts in a row do not add up, and how to work out the real total discount with a simple multiplication.

Work out a tip percentage quickly in your head, then divide the total fairly between friends.

Convert kilograms to pounds and stones accurately with the 2.20462 factor and a mental shortcut for travel and fitness.

Prefer longer guides? See Articles, or find short answers in the FAQ.

By country

Guides for your location: Pakistan · India · United States.