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.
51 articles, page 4 of 5
Electrolytes and Hydration: When Water Alone Is Not Enough
Sweat carries sodium, not just water. Here is when replacing it matters, what the sodium concentration data shows, and why most people need electrolytes far less often than marketing suggests.
Stress, Cortisol and Weight: Untangling a Badly Oversold Story
Cortisol is not a fat-storage switch. Chronic stress does affect body weight, but through sleep, eating and movement rather than a direct hormonal route.
One-Rep Max Testing: Estimate It or Test It?
Four published equations estimate your one-rep max from a submaximal set, and they disagree by several kilos. Here is what that spread means and when to test.
Pregnancy Weight Gain: What the Guidelines Actually Say
The IOM ranges are set by pre-pregnancy BMI, not by weight during pregnancy. Here is where those numbers came from, what they do and do not predict, and why your target belongs to your care team.
Heart Rate Training Zones: What Each Zone Actually Trains
Five training zones, and the specific physiology each one develops. How the bands are calculated, why your resting pulse changes them, and where they mislead.
Calorie Needs: How the Equations Work and How to Calibrate Them
Every TDEE calculator gives you a confident-looking number produced by a regression fitted to strangers. Here is what the equations estimate, where the error hides, and how to correct the figure against your own data.
Body Fat Percentage vs BMI: Which Number Actually Matters?
Body fat percentage describes what your body is made of. BMI describes how heavy you are for your height. Here is when each one earns its place, and where both fail.
Sleep and Metabolism: What Short Sleep Does to Appetite and Training
Short sleep raises hunger, shifts what you lose on a diet from fat toward lean tissue, and blunts training quality. Here is what the controlled trials found.
How Accurate Is Calorie Tracking? The Error Sources Nobody Mentions
Tracked intake is typically wrong by ten to thirty percent, and the errors run one way. Here is where they come from and why tracking is still worth doing.
How Many Calories Should You Eat? Working From BMR to a Real Target
A calculator gives you a maintenance estimate. Turning it into a daily target means choosing a deficit, respecting a floor, and reading the feedback.
What BMI Actually Measures, and What It Misses
Body mass index is a population screening tool that was never designed to describe an individual body. Here is what the index does well, where it fails, and which measurements to add.
Waist-to-Height Ratio: The Simplest Risk Marker You're Not Using
Keep your waist under half your height. One tape measure, one division, no reference population needed, and it holds up against BMI on cardiometabolic risk.
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.
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