The Calclu blog
The stories behind the numbers — practical, plain-English deep dives into the math of health, money and everyday life, each paired with a free calculator you can use right away.
Understanding Your BMI: What the Number Actually Tells You
Your BMI is one number, but it opens a window onto your health risks and your healthy weight range. Here's how it's calculated, what the ranges mean, and where the formula falls short.
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How Many Calories Do You Actually Need? A Complete Guide
Forget the generic 2,000-calorie advice. Here's how to calculate your real daily calorie needs from your BMR, activity level, and goals — plus how to split them into macros.
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Loan Interest Explained: How Your Monthly Payment Is Really Calculated
Every mortgage, car loan, and personal loan uses the same amortization formula. Here's how your monthly payment is calculated — and why half a percent costs you a fortune.
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The Power of Compound Interest: Why Starting Early Beats Saving More
Why does saving $100 a month starting at 25 beat starting at 35 by over $140,000? Compound interest. Here's the formula, the Rule of 72, and the dark side nobody mentions.
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Percentages Made Simple: Tips, Discounts and Everything In Between
From tips to discounts to "is this a good deal?", percentages run daily life. Here are the five percentage situations you'll actually meet — and the traps that catch everyone.
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How Old Are You Really? Age Calculation Beyond Birthdays
Born March 15, 1990 — how old are you today? The answer changes with one rule, and getting it exactly right matters for pensions, school cutoffs, and legal deadlines.
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The Complete Guide to Tipping and Splitting Bills Fairly
The check lands and the table goes quiet. Here's how to tip confidently (the 10% + half trick), split the bill three fair ways, and settle the classic arguments.
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How Due Dates Are Calculated: The Science Behind Your Estimated Delivery Date
Only 4% of babies arrive on their due date — yet the date drives everything. Here's how Naegele's 280-day rule works, why ultrasound corrects it, and why weeks beat months.
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GPA Explained: How It's Calculated and Why Credit Hours Are Everything
A 3-credit A and a 1-credit C don't average to 2.5 — the A weighs three times more. Learn the weighted-average math behind your GPA and how to use it strategically.
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Standard Deviation Made Simple: Reading the Story in Your Data
Two students average 75. One scores 74-75-76, the other 60-75-90. Same mean, different story — standard deviation is the statistic that tells them apart.
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Body Fat Percentage: The Number the Scale Can't Give You
Two people weigh 80 kg — one is an athlete, one carries visceral fat. The scale can't tell them apart, but body fat percentage can. Here's how to measure and use it.
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How Much Water Should You Drink? What the Science Actually Says
"8 glasses a day" was never really science. Your real hydration needs come from your weight, activity, and climate — plus two signals your body already gives you.
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