AllCalcNow Blog

Learn how to calculate age from a date of birth. Discover the manual subtraction formula, borrow rules for months and days, and see worked examples.

Learn how to calculate the exact number of days between two dates. Review manual month-summing, Julian Day Number formulas, and worked examples.

Learn how pregnancy due dates are calculated. Review Naegele's rule, IVF transfer date adjustments, and see step-by-step worked calculations.

Learn how to calculate work tenure, service years, and anniversaries. Review proportional year formulas, leap year adjustments, and see worked examples.

Understand the mathematical rules of leap years. Learn why we have leap days, review the Gregorian divisibility algorithm, and see worked examples.

Compare 4 common methods to measure body fat percentage. Learn the US Navy formula, review worked examples, and check accuracy ranges.

Compare BMI and Body Fat Percentage. Learn why BMI can be misleading for athletes, understand metabolic risks like TOFI, and see worked examples.

Learn how to calculate your BMR and TDEE. Review the Mifflin-St Jeor formula, calculate activity factor adjustments, and see worked examples.

Learn how to calculate a healthy weight range by height using reverse BMI equations. Compare standard boundaries and the Devine formula with worked examples.

Learn how to track body composition without relying on a weight scale. Understand body recomposition, circumference measurements, and athletic benchmarks.

Learn the difference between markup and margin. Study the formulas, review worked pricing examples, and optimize your business profits.

Learn the math to split restaurant bills fairly. Calculate proportional tax and tip, divide shared appetizers, and review worked group examples.

Access our comprehensive unit conversion cheat sheet. Learn formulas for length, weight, volume, and temperature, and see worked examples.

Learn how to calculate price per unit to find the best deal. Compare bulk vs standard sizes, spot shrinkflation, and review worked shopping examples.

Discover why manual percentage math doesn't always align with pocket calculators. Study percentage asymmetry, calculator % key logic, and worked examples.

Learn the formulas to calculate discounts, sale prices, and total savings. See worked examples for single, stacked, and reversed discounts.

Learn standard formulas to convert length, weight, and temperature between metric and imperial systems. Study worked examples and quick math shortcuts.

Learn how to calculate your vehicle's fuel cost and MPG. Study worked road trip examples, compare vehicle efficiencies, and save on gas.

Learn how to calculate your Grade Point Average (GPA). Understand weighted vs unweighted scales, study credit-weight formulas, and see worked examples.

Learn tipping customs and gratuity rules for restaurants, hotels, and taxis worldwide. Check regional guides, see worked examples, and avoid travel mistakes.

Discover the differences between simple and compound interest. Study the formulas, see side-by-side growth examples, and learn how compounding accelerates returns.

Compare fixed vs variable rate loans. Learn how variable rate resets are calculated, see rising and falling rate scenarios, and find the best loan.

Understand the difference between APR and interest rate. Learn how upfront loan fees affect APR, study worked examples, and make smarter borrowing choices.

Learn how to calculate your Debt-to-Income (DTI) ratio. Understand front-end vs back-end ratios, review lender guidelines, and see worked examples.

Compare renting vs buying a home. Learn the price-to-rent ratio formula, understand break-even timelines, and see step-by-step worked calculations.

Learn the exact formula to calculate Equated Monthly Installments (EMI), understand loan amortization schedules, and see step-by-step worked examples.

Learn the difference between gross and net salary, understand tax deductions and pre-tax benefits, and see step-by-step take-home pay calculation examples.

Understand how currency pairings and exchange rates work. Learn conversion formulas, calculate spreads and retail fees, and see worked examples.

Determine your ideal retirement savings rate using math. Learn the future value annuity formula, review age-based savings benchmarks, and see worked examples.

Understand how to calculate your electricity bill. Learn to convert Watts to kWh, analyze utility rates, and see step-by-step cost examples.

Ready to buy a home or refinance? Learn how to calculate your monthly payment manually using the amortization formula and see how PITI affects your costs.

Learn the math behind Body Mass Index (BMI). We break down metric and imperial formulas, check official WHO categories, and look at the health limitations of BMI.

Discover the mathematical formula for compound interest, compare simple and compound returns, understand compounding frequencies, and see the power of starting early.

Understand Value Added Tax (VAT), compare it to sales tax, learn the exact formulas to add or remove VAT, and review standard VAT brackets in the UK and Europe.

Tipping customs vary wildly across the globe. Learn the mathematics of tipping, discover local etiquette rules for popular travel destinations, and split bills easily.

Retirement planning doesn't have to be overwhelming. Learn how to estimate your target savings, understand standard withdrawal rules, and take control of your financial future.

We standardly measure our age in years. But looking at your lifespan in days, weeks, or hours provides a completely new perspective. Learn the math of dates.

Percentages are a fundamental part of daily math. Master percentage calculations with 3 simple methods for everyday calculations, change rates, and ratios.