🧮Calculators

Several tips in the book are really a calculation. These tools use the rules and numbers the book gives; afterwards, go back to the tip for the full explanation and sources.

• 💳 The real annual rate of installment plans What a fee of “0.6% per month” costs per year, using the method of China’s central bank. Don't make only the minimum credit card payment, and don't take installments or consumer loans for purchases; if you must borrow, convert the interest into an annualized rate before comparing
• 🧮 Is paying off a mortgage early worth it How much interest an early payment saves, compared with what you could reliably earn instead. Before prepaying your mortgage, work through one comparison; don't go by feel
• ☕ How much caffeine today Coffee, tea, cola and energy drinks added up and compared with the 400 mg daily limit. Drink 3 to 4 cups of coffee a day, keep total caffeine under 400 mg, and don't add sugar or milk foam
• 🍺 How much pure alcohol per week Beer, wine and spirits converted to grams of pure alcohol and compared with the book’s bands. To drink less, first count how much you drink in a week, then spend a few minutes talking to a doctor