Guides
Health & Fitness Guides
23 plain-language answers to the questions behind the numbers — each one paired with the free calculator that puts it to work.
Body composition
What BMI, body fat and lean mass actually measure — and where each one misleads.
What Is a Healthy BMI? Chart, Ranges and Limits The healthy BMI range, the full category chart, and where BMI falls short. Read the guide → How to Measure Your Body Fat Percentage The tape, caliper, BIA and DXA methods compared — plus healthy ranges. Read the guide → What Is a Good FFMI? The Natural Muscle Limit The FFMI ranges for men and women, the natural muscle limit, and how to read yours. Read the guide → Waist-to-Hip Ratio and Your Health What WHR says about health, the WHO risk thresholds, and how it compares to BMI. Read the guide → What Is a Good Waist-to-Height Ratio? The "half your height" rule, the NICE risk bands, and how WHtR compares to BMI. Read the guide → Waist-to-Height Ratio Chart: Your Target Waist by Height Keep your waist under half your height. This chart turns that ratio into an actual waist measurement for your height, in cm and inches. Read the guide → How Long Does It Take to Build Muscle? Months, not weeks — and your first month of gains is mostly not muscle. Read the guide →
Calories & energy
Where your daily burn comes from, and what a deficit does over weeks rather than days.
How Long Does It Take to Lose Weight? The math behind realistic timelines, worked examples, and why loss slows down. Read the guide → What Is a Calorie Deficit? The Simple Science The one mechanism behind all fat loss, how it works, and how to size it safely. Read the guide → How Many Calories Does Walking Burn? Body weight and pace decide almost everything — here is the honest MET math, in charts. Read the guide → How to Speed Up Your Metabolism: What Works The honest, evidence-based guide to boosting metabolism — and what barely works. Read the guide → How Many Calories Are in a Pound? About 3,500 for a pound of fat — but not for a pound of muscle, or a pound on the scale. Read the guide → How Many Steps Are in a Mile? About 2,200–2,400 for most adults. The popular 2,000-step rule only fits a 6'5" walker. Read the guide → The Mifflin-St Jeor Equation, Worked by Hand The equation, worked by hand — and the detail almost every page about it gets wrong. Read the guide → What Does kcal Mean? Kilocalorie. On a label it is the same thing as a capital-C Calorie — here is why both exist. Read the guide →
Nutrition & hydration
Protein, carbs, macros, fasting and fluid — how the common targets were arrived at.
How Much Water Should You Drink a Day? The real answer beyond '8 glasses' — how much fluid you actually need and why. Read the guide → How to Count Macros for Cutting and Bulking Turn a calorie target into grams of protein, carbs and fat — for cutting or bulking. Read the guide → How Much Protein Do You Need a Day? The g/kg targets for your goal, how to split protein across meals, and where to get it. Read the guide → Intermittent Fasting for Beginners How 16:8 and other methods work, how to start safely, and what breaks a fast. Read the guide →
Fitness & performance
Strength standards, running pace, heart-rate zones and what the numbers predict.
How to Calculate Your One-Rep Max The Epley and Brzycki formulas, a worked example, and how to train with %1RM. Read the guide → How to Lower Resting Heart Rate: What the Evidence Shows Aerobic training does most of the work — about 4 bpm in pooled trials. Strength training alone does little. Read the guide →
Everyday health
Sleep, recovery and life-stage questions the calculators touch on.
Can You Catch Up on Sleep? Recovery sleep helps, but three nights of eight hours did not restore baseline in the study that tested it. Read the guide → How Is a Due Date Calculated? A Simple Guide Naegele's rule, ultrasound dating, and why only about 4-5% of babies actually arrive on the due date. Read the guide →