FourLabs Blog
Practical, in-depth guides on the math, formulas and conventions behind every FourLabs tool — organized into our four labs.
Text Lab
- Text LabJun 15, 2026 5 min
UPPERCASE, camelCase, snake_case & Slugs: When to Use Each
A practical guide to text case conventions: when to use Title Case in headings, camelCase in JavaScript, snake_case in databases and kebab-case in URLs.
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- Text LabJun 25, 2026 7 min
Find and Replace with Regex: A No-Nonsense Cheat Sheet
The regex patterns that pay for themselves: emails, phone numbers, whitespace cleanup, capture groups and the difference between greedy and lazy matching.
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- Text LabJun 26, 2026 5 min
Invisible Text: How It Works, Where It Works, Where It Doesn't
Which Unicode characters render as blank space, which platforms strip them, and why your blank WhatsApp message sometimes refuses to send.
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- Text LabJun 21, 2026 8 min
Writing Numbers in Words: Checks, Invoices & Legal Documents
Why amounts are written twice on cheques, the exact phrasing banks expect, and how the same rules apply to invoices, loan agreements, contracts and tax forms in the US, UK and India.
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Daily Tech Lab
- Daily Tech LabJun 12, 2026 6 min
How to Calculate Your BMI Correctly (Formula, Chart & Examples)
Step-by-step guide to calculating Body Mass Index with the metric and imperial formulas, WHO categories, worked examples, and the limits of BMI.
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- Daily Tech LabJun 20, 2026 5 min
Percentage Calculator Guide: Increase, Decrease & Tip Math Made Simple
Master the three core percentage formulas — what is X% of Y, X is what % of Y, and percent change — with real-world examples for tips, discounts and tax.
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- Daily Tech LabJun 18, 2026 4 min
How to Calculate Your Exact Age (Years, Months, Days & Leap Years)
The simple method to calculate age in years, months and days — including how leap years and month-length differences affect the result.
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- Daily Tech LabJun 22, 2026 8 min
Calorie Calculator Explained: BMR, TDEE & Macro Targets
What BMR and TDEE actually mean, the Mifflin–St Jeor formula, activity multipliers, and how to set protein, carb and fat targets for any goal.
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Conversion Lab
- Conversion LabJun 5, 2026 7 min
Metric vs Imperial: A Practical Comparison (with Conversion Tables)
Why the world uses two measurement systems, how kilograms, pounds, meters, and feet really compare, and the fastest way to convert between them.
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- Conversion LabJun 24, 2026 6 min
Celsius, Fahrenheit & Kelvin: Formulas, Reference Points & Memory Tricks
The exact formulas for converting between Celsius, Fahrenheit, Kelvin, Rankine and Réaumur, plus reference points every cook, traveller and student should memorise.
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Dev & Design Lab
Coming Soon
New developer and design guides are loading. Stay tuned.