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 5 of 5
How to Find Your Max Heart Rate: Formulas, Field Tests and Their Error Bars
Age formulas estimate maximum heart rate to within roughly ten beats. Here is how Fox, Tanaka and Gellish differ, what a field test adds, and what it costs you.
How Much Water Should You Drink? Past the Eight-Glasses Myth
The eight-glasses rule has no research behind it. Here is what the reference bodies actually publish, what a body-weight formula adds, and why thirst beats both.
Gestational Age Explained: Why Pregnancy Is Dated From Before Conception
Pregnancy is counted from the last menstrual period, a fortnight before conception. Here is why that convention exists, what Naegele's rule assumes, and why dating is a window.
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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