How to Improve Fuel Economy: Driving Habits That Actually Save
Smoother driving, correct tire pressure, less weight and lower motorway speed can cut fuel use noticeably. Here is what each one is worth.
Marco Bianchi · 5 min read
Guides & tutorials
Practical guides, how-tos and comparisons to get the most out of our free online tools.
June 1, 2026
How Long Does It Take to Read a Book?
Estimate reading time from word count and reading speed. Learn the simple formula, the average of about 250 words per minute, and a worked example for a full novel.
Lena Hoffmann · 4 min read
May 29, 2026
EBITDA vs EBIT vs Net Income: One P&L, Three Answers
Walked down one $10M P&L: EBITDA of $1.8M, EBIT of $1.1M, net income of $525K. The gap is 70.8 percent of EBITDA — and it is the cost of the assets and the debt the business actually runs on.
Camille Laurent · 7 min read
What TV Size Is Right for My Room?
Turn your viewing distance into a recommended screen diagonal in inches, so a 4K TV fills your field of view without straining your eyes.
Marco Bianchi · 4 min read
What Is a Child Growth Percentile?
Growth percentiles compare a child's height and weight to others the same age and sex. Here's how to read them and what really matters.
Sofia Nunes · 2 min read
May 28, 2026
What LTV:CAC Ratio Should You Target? The Churn Estimate Decides It
Everyone quotes 3:1 and nobody states their churn assumption. With $100 ARPU and an 80 percent gross margin, moving monthly churn from 2 to 3 percent drops the ratio from 4.0:1 to 2.67:1 — a pass turned into a fail by one percentage point.
Camille Laurent · 8 min read
How to Split Rent Fairly Between Roommates
Three fair ways to split rent — equally, by room size, or by income — with worked examples so nobody feels shortchanged.
Camille Laurent · 4 min read
May 27, 2026
What Is the Rule of 40? Six Ways to Score Exactly 40
Growth rate plus profit margin should clear 40. But 60 percent growth at a minus 20 percent margin scores the same as 10 percent growth at a 30 percent margin — and on $10M of revenue those are opposite companies.
Camille Laurent · 8 min read
How Many Teaspoons in a Tablespoon?
There are exactly 3 teaspoons in 1 tablespoon. Learn the exact conversion, the milliliter equivalents, and why US, UK, and metric spoons differ slightly in size.
Marco Bianchi · 3 min read
The 10% Rule for Runners: Build Mileage Without Injury
The 10% rule says to raise your weekly running mileage by no more than 10% at a time. Learn why it works, when to break it, and how to plan safe progression.
Aisha Karim · 4 min read
How to Estimate Your Conception Date
Estimate conception from your last period or your due date, understand ovulation timing, and know why the result is a range rather than a single day.
Sofia Nunes · 4 min read
May 26, 2026
Three Different Rules Get Called "The 529 Rule"
Qualified expenses, the K-12 cap and state tax treatment are three separate rules, and only the first two are federal. The K-12 cap doubled to 20,000 dollars for tax years from 2026; a federally qualified withdrawal can still be a state recapture event.
Camille Laurent · 15 min read