SpecWhale guides

Why your first loan payment is mostly interest, how the split shifts over time, and how to use that to pay less interest overall.

BMI is a population-screening ratio, not a diagnosis. Here's what the number actually represents and where it tends to mislead.

What a /24 actually means, how to find your usable host range fast, and the two host counts everyone forgets to subtract.

A 50% markup and a 50% margin are not the same number. Here's the difference, and why it matters when you're pricing a product.

Both are plain text and both move data between systems. The right choice depends on whether your data is a table or a tree.

Some holidays move every year, some are regional even within one country, and a few countries swap official observance days entirely.

BMI, the Navy tape method, and skinfold calipers all estimate body fat differently -- and disagree with each other more than most people expect.

Length beats complexity rules almost every time. Here's why entropy, not special characters, is the number that matters.

Most regex bugs come from four things: greedy quantifiers, missing anchors, unescaped special characters, and forgetting a pattern matches anywhere by default.

Why cropping to a new aspect ratio always costs you either width, height, or resolution -- and how to figure out which before you shoot or export.

Your tax bracket is not your tax rate. Here's what each of these three numbers actually measures.

The 220-minus-age formula is the one everyone knows and the one exercise scientists trust least. Here's what the alternatives fix.

An inch is exactly 2.54 cm by definition. A cup of flour in grams depends on how you scoop it. That difference matters more than it sounds.

WCAG contrast ratios aren't a subjective 'looks readable' judgment -- they're a calculated ratio with a specific formula and specific pass/fail thresholds.

Both add a percentage at purchase, but VAT is collected in stages throughout the supply chain while sales tax is collected once, at the final sale.

VO2 max measures how much oxygen your body can use during exercise. Pace measures how fast you cover distance. They're related, but not the same thing.

There are over 60 official HTTP status codes. In practice, a handful cover almost everything you'll actually debug.

Storage manufacturers use decimal gigabytes. Operating systems display binary gibibytes. Both numbers are correct -- they're just measuring with different rulers.

"Ships in 5 days" usually means business days. "Due in 5 days" usually means calendar days. Mixing them up is a common source of missed deadlines.

These three formats solve different problems -- structure, tabular simplicity, and safe transport -- and picking the wrong one is a common source of avoidable headaches.

Both measure what's left after cost of goods. The difference is whether you're looking at dollars or percentage of revenue.

APR ignores compounding. APY includes it. That gap is why the same loan can show two different-looking interest rates.

Simple interest grows linearly. Compound interest grows exponentially. The difference is small early, large over time.