Guides

Plain-English explanations with worked examples. Each guide links to the calculator that does the work for you.

• BMI vs Body Fat Percentage: Which Should You Use? BMI is a quick weight-for-height screen; body fat percentage shows what the weight is made of. See when each helps, with a worked example.
• How to Count Days Between Two Dates (and Avoid Off-by-One Errors) Should you count the start day, the end day, or both? Learn the simple rule, with worked examples for leap years and weekends.
• Metric to Imperial Conversion Chart (Printable) A printable metric and imperial conversion chart for length, weight, volume and temperature, using exact official definitions, US and UK units labelled.
• How to Pay Off a Loan Faster: What Extra Payments Really Save See how much paying a little extra each month saves on a loan, with a worked example, a comparison table and what to check with your lender first.
• Percent vs Percentage Points: What’s the Difference? Why a rise from 10% to 12% is 2 percentage points but a 20% increase. Clear examples from interest rates, prices and tax, plus common mistakes.