How Inflation Eats Your Savings
Inflation quietly cuts what your money can buy. Here's what it is, how it erodes cash, the rule of 72 for prices, and how to protect your savings.
Camille Laurent · 3 min read
Guides & tutorials
Practical guides, how-tos and comparisons to get the most out of our free online tools.
August 7, 2025
August 6, 2025
How to Count Business Days
Business days are weekdays minus holidays. Here's what counts, how to work them out between two dates, why holidays complicate it, and where it matters.
Lena Hoffmann · 3 min read
How to Scale a Recipe Up or Down
Multiply every ingredient by the same factor. Here's how to find it, why the ratios must stay fixed, what doesn't scale linearly, and how to round sensibly.
Marco Bianchi · 3 min read
August 5, 2025
How to Calculate a Weighted Average
A weighted average gives some values more influence than others. Learn the Σ(w·x) / Σw formula with grade and portfolio examples you can follow step by step.
Lena Hoffmann · 3 min read
August 4, 2025
What Week Number Is It?
Week numbers run from 1 to 52 or 53. Here's how the ISO 8601 system numbers them, why some years have 53 weeks, and where businesses use them.
Lena Hoffmann · 3 min read
August 1, 2025
How Long Will It Take to Download a File? Time, Bits vs Bytes, and Overhead
Estimate download time from file size and connection speed. Learn the size ÷ speed formula, the crucial bits-versus-bytes conversion (divide by 8), and why real downloads run slower than the math predicts.
Daniel Okonkwo · 4 min read
Sales Tax vs VAT: The Difference
Both tax what you buy, but collect it differently. Here's how US sales tax and VAT work, and what each means for the price you actually pay.
Camille Laurent · 3 min read
July 31, 2025
How to Pace Your Swim
Swimming pace is measured per 100 metres. Here's how to work it out, why even pacing wins, how the pace clock helps, and how to get faster.
Aisha Karim · 3 min read
July 30, 2025
How to Estimate Your Electricity Bill
Your bill is energy used times the price, plus a standing charge. Here's how to work out kWh, what the standing charge is, what uses the most, and how to cut it.
Marco Bianchi · 3 min read
July 29, 2025
PSI to Bar: Convert Tire Pressure Both Ways
Convert PSI to bar and back with the exact factor, learn the 1 bar ≈ 14.5 PSI shortcut, and set tire pressure right in either unit.
Daniel Okonkwo · 4 min read
July 28, 2025
Combinations vs Permutations: When Order Matters
The difference between combinations and permutations comes down to one question: does order matter? Learn the nCr and nPr formulas with clear worked examples.
Lena Hoffmann · 3 min read
What Is a Cron Expression?
A cron expression schedules a task to run automatically at set times. Here's what it's for, its five fields, how to read one, and the common gotchas.
Daniel Okonkwo · 3 min read