Guides
Clear explanations of the maths behind everyday decisions, each with a worked example and a free calculator to try your own numbers.
Compound interest explained: how money grows on itself
What compound interest is, the formula behind it, the Rule of 72, and why starting early matters more than the amount you save.
From yearly salary to hourly rate — and what you really take home
How to convert an annual salary to an hourly wage, the difference between gross and net pay, and how to compare a job offer with freelance rates.
How VAT works — adding it, removing it and avoiding the classic mistake
Learn how value-added tax is calculated, how to remove VAT from a gross price correctly, and how VAT differs from US sales tax.
How a mortgage payment is calculated — and where your money goes
The annuity formula behind monthly mortgage payments, how interest and principal shift over time, and how term and rate change the total cost.
Percentages made easy: the three questions you'll ever need
How to calculate a percentage of a number, a percentage change, and reverse percentages — plus why a 50% drop needs a 100% rise to recover.
BMI and body fat percentage: what they measure and their limits
How BMI is calculated, the WHO categories, why muscular people can score 'overweight', and how body fat estimates and waist size add context.
Smart shopping: how discounts really add up
Why 20% + 10% off is not 30% off, how to compare 'buy one get one' deals, and how to work out the true price per unit.
Inflation and the real value of money
What inflation is, how it erodes savings, how to calculate real returns, and how to adjust past prices to today's money.