Guides
Clear explanations of how each calculation works, with worked examples you can open in the matching calculator.
Quadratic FormulaHow to Use the Quadratic Formula (Step by Step, with Examples)Learn the quadratic formula in plain English: when to use it, how to plug in a, b and c, what the discriminant tells you, and five worked examples.Read the guide SlopeHow to Find the Slope of a Line (Formula, Steps & Examples)Find the slope (gradient) of a line from two points, a graph or an equation. Clear steps, worked examples, and the mistakes that trip people up.Read the guide PercentageHow to Calculate a Percentage (The 3 Questions, with Examples)Work out a percentage of a number, what percent one number is of another, and percentage change. Plus reverse percentages, VAT and common traps.Read the guide BMIHow to Calculate BMI (Metric, Imperial and Stone) and What It MeansCalculate BMI by hand in kg and m, pounds and inches, or stone. See the healthy ranges, when lower thresholds apply, and what BMI can't tell you.Read the guide