Guides
Original long-form articles on everyday calculations and the mistakes people make with them.
- Six Unit-Conversion Traps: Ounces, Gallons, Tons and Temperature Gaps
An ounce of weight and a fluid ounce differ 28-fold, US and UK gallons differ 20%, and three different tons differ by 10%. How to avoid each trap.
- How Big Should an Emergency Fund Be? Making "3–6 Months" Concrete
Work out your own emergency-fund number from income stability, dependants and fixed costs — plus where to keep it and when to use it.
- Measuring Body Fat: Four Methods, Their Errors and When to Use Them
How far apart are smart scales, calipers, tape formulas and DEXA? Their error sources, how to measure properly, and why trends beat absolutes.
- Prepay the Mortgage or Invest? A Numbers-First Decision
Convert prepayment into an equivalent risk-free yield, then compare it with your after-tax returns, liquidity and peace of mind.
- Mean, Median and Mode: Which One to Use
Why averages mislead, using income and housing examples to show when mean, median or mode is the right summary.
- Percentages and Percent Change: Three Common Errors
Telling percentage from percentage points, getting the direction right, and avoiding the discount/markup symmetry trap.
- TDEE and Fat Loss: How Large Should the Deficit Be?
From BMR to TDEE, activity multipliers, deficit sizing and plateaus — a sustainable framework for fat loss.
- The Limits of BMI: Why It Is Not Body Fat
BMI is just weight over height squared. Why it mislabels athletes and older adults, and how waist and body-fat measures fill the gap.
- The Power of Compounding: Time, Rate and Regular Investing
The compound interest formula, the Rule of 72, and how lump sums differ from monthly contributions over time.
- How Mortgage Payments Work: Amortization, Rates and Terms
From the amortization formula to how rates, terms and down payments affect monthly payments and total interest.