Guides that explain the numbers
A calculator hands you a figure. It rarely tells you which population the equation was built on, how wide the error bars are, or what the number fails to capture. These guides cover that ground, citing the original papers so you can go and read them.
When a Health Number Warrants a Doctor's Visit
Calculators are screening prompts, not diagnoses. Here are the categories of result that deserve a professional opinion, and how to make that appointment useful.
More guides
Strength Training for Beginners: The First Twelve Weeks
Beginners adapt to almost anything, so the programme matters less than showing up. Here is what to do for twelve weeks, what to ignore, and why less is more at the start.
Carbohydrates and Fibre: Setting an Intake That Fits Your Training
Carbohydrate has no minimum requirement but it fuels hard work, so the right intake follows your training volume rather than any fixed percentage of calories.
RPE and Reps in Reserve: Autoregulating Load Without a 1RM Test
Reps in reserve turns effort into a number you can programme against. How the scale works, how accurate it is, and why novices systematically misread it.
Eating for Muscle Gain: Surplus Size, Protein, and the Rate You Can Actually Build
Muscle gain is limited by how fast you can build tissue, not by how much you eat above maintenance. Here are the real rates and the surplus that supports them.
Body Recomposition: Losing Fat and Gaining Muscle at the Same Time
Losing fat while adding muscle is possible, but not for everyone equally. Here is who it works for, what the trials show, and why the scale stops being useful.
Reverse Dieting: Separating the Mechanism From the Marketing
Reverse dieting claims to raise your metabolism by slowly adding calories. The underlying physiology is real; the promised effect size is not. Here is the difference.
Returning to Exercise After Birth: A Staged, Evidence-Led Approach
The six-week check is a clearance, not a starting line. Here is what the guidelines say about postpartum activity, how return is usually staged, and who to ask.
Understanding Health Metrics: How to Read a Number Without Overreacting to It
Every health number carries a population of origin, an error range and a threshold drawn by committee. Here is how to read one without overreacting to it.
Dietary Fat: How Much You Need and Why a Floor Exists
Two fatty acids are genuinely essential and fat carries the vitamins that need it. That is why a fat target has a hard minimum rather than only an upper bound.
How to Start Running Without Getting Injured in Week Three
Your fitness improves faster than your tendons and bones can follow. That mismatch is why new runners break down, and why the fix is about patience, not form.
Ideal Body Weight Formulas Compared: Why Four Equations Give Four Answers
Devine, Robinson, Miller and Hamwi disagree by several kilograms at the same height. The reason is that none of them was built to describe a healthy weight.
Read the guide, then run the numbers
Each article links to the calculators it discusses, and each calculator shows the equation and source behind its output. Every article carries a named author and a publication date. Nothing here is medical advice. Our editorial policy sets out how we source, review and correct what we publish.
Open the toolkit