Activity Multipliers: How to Pick the Right One for Your TDEE
The activity factor you choose changes your calorie estimate far more than the BMR equation does. Here is what each level means and how to avoid the usual overestimate.
Health & Fitness
Body measurements, calories, sleep and training numbers, and what they do and do not tell you.
BMI for Children and Teens: Why Percentiles Replace Cutoffs
A child's BMI is calculated like an adult's, but it is judged against other children of the same age and sex. Here is how percentiles work and what the bands mean.
Mifflin-St Jeor vs Harris-Benedict vs Katch-McArdle for BMR
Different BMR equations give different answers for the same person. Compare Mifflin-St Jeor, Harris-Benedict and Katch-McArdle on one set of numbers and see why they differ.
How to Calculate Time Slept and Sleep Efficiency
Time in bed and time asleep are not the same number. Learn to calculate both, handle the midnight crossing, and compute sleep efficiency by hand.
Calorie Deficit Math: Setting a Target and Estimating a Timeline
A daily calorie deficit converts into a predicted rate of weight loss with simple division. Here is the arithmetic, why the plan slows down over time, and where the limits are.
How Calories Burned Are Estimated: METs Explained
Most calorie-burn figures come from one short formula built on MET values. Learn how it works, how to use it by hand, and why the answer is an estimate.
Estimate Your One-Rep Max: Epley, Brzycki and Their Limits
You do not need to grind out a true single to know roughly how strong you are. Two simple formulas turn a set of 3 to 10 reps into a one-rep max estimate.
Healthy Weight Range for Your Height: How It Is Calculated
A healthy weight range is a BMI band turned back into kilograms. Here is the arithmetic, a table for common heights, and why a range beats a single ideal number.
Heart Rate Zones: Percent of Max vs Heart Rate Reserve
Heart rate zones turn "how hard am I working?" into numbers. Learn the two common ways to calculate them and why the same percentage can mean two different heart rates.
How Much Water Do You Need? Guidelines and a Simple Estimate
There is no single right amount of water. Here is what official intake guidelines say, how to estimate a range from body weight, and when needs go up.
How to Calculate BMI by Hand in Metric and Imperial Units
BMI is one division and one squared number. Here is the metric and imperial method, the common unit slips, and how to run the formula backwards to find a target weight.
How to Estimate Body Fat With a Tape Measure (US Navy Method)
A soft tape and a log button are enough to estimate body fat. Here is the US Navy method step by step, what the percentage means, and how far to trust it.
Predict Your Race Time with the Riegel Formula
A 5K time can hint at your marathon time, but not by simple multiplication. The Riegel formula adds a fatigue factor, and it comes with real caveats.
Resting Heart Rate Trends: A Simple Recovery Check
A morning pulse count costs nothing and can hint at how well you are recovering. The trick is to compare it with your own baseline, not with anyone else's.
Running Pace Explained: Per Km, Per Mile and Speed
Pace is time per distance, speed is distance per time, and they are two views of the same number. Here is how to calculate and convert them by hand.
Sleep Cycles and Bedtimes: Working Out When to Sleep
Count back from your wake-up time in blocks of about 90 minutes to find a sensible bedtime. Here is the arithmetic, a quick-reference table and what the method cannot promise.
Sleep Debt: How to Calculate It and Pay It Back
Sleep debt is simple bookkeeping: hours needed minus hours slept. Here is how to total it for a week and spread the repayment sensibly.
Waist Measurements: Waist-to-Height and Waist-to-Hip Ratios
A tape measure can say more about abdominal fat than the bathroom scale. Learn where to measure, the common cut-offs, and how to calculate both ratios by hand.
The 10% Rule for Weekly Mileage and Recovery Weeks
Raising mileage by 10 percent a week sounds modest until you see it compound. Here is the maths, the limits of the rule, and a simple cut-back week pattern.
What BMI Can and Cannot Tell You About Your Health
Two people can share the same BMI and have very different bodies. Here is what the number was designed for, where it falls short, and what to pair it with.