Practical guides, how-tos and comparisons to get the most out of our free online tools.
A practical guide to pricing: work out your unit cost, apply cost-plus pricing, understand markup versus margin, and know when to price on value instead.
Daniel Okonkwo · 4 min read
Running pace is time per kilometre or mile. Here's how to work it out from any run, convert between units, and use it to pace a race without blowing up.
Aisha Karim · 3 min read
ERA measures what happened, FIP measures only what the pitcher controls without his fielders, WHIP measures traffic allowed. Two pitchers can swap places entirely between them — and the gap between ERA and FIP is a forecast, not a verdict.
Aisha Karim · 10 min read
Estimate paint by wall area, coats and the coverage on the tin — with a worked example and the 10% rule so you buy once and match the colour.
Marco Bianchi · 2 min read
OPS adds two fractions with different denominators, which as arithmetic is indefensible. It survives because it tracks run scoring far better than batting average and costs nothing to compute — but it underpays on-base ability, and OPS+ does not fix that.
Aisha Karim · 10 min read
Mean, median and mode all describe the 'middle' of your data — but answer different questions. Here's what each means, with examples and when to use which.
Lena Hoffmann · 2 min read
Published best-time tables average over audiences that are not yours, and on a ranked feed posting time matters far less than it did on a chronological one. Compute your own audience's activity across time zones instead — six zones flatten the timing lever from a 94% swing to a 22% one — and see how many posts a real timing test needs.
Camille Laurent · 12 min read
Field goal percentage counts a three-pointer and a layup as the same event and ignores free throws entirely. eFG% fixes the first problem, TS% fixes both — and the ranking of three players changes at every step.
Aisha Karim · 10 min read
Platforms crop rather than letterbox, so an image is only safe if its subject sits inside the intersection of every ratio it will be shown at. That intersection has a closed form — the narrowest ratio divided by the widest — and it works out at 29.45% of the source for a realistic set. Geometry that does not expire, plus the pixel counts that do.
Camille Laurent · 12 min read
Turning jump height into take-off velocity is exact physics. Turning it into watts is a regression fitted on somebody else's athletes — and the three common formulas disagree by thousands of watts on the same jump.
Aisha Karim · 13 min read
The famous email ROI multiples are self-reported survey figures with the labour left out of the denominator and revenue that would have arrived anyway left in the numerator. Build the honest version instead: incremental revenue against full cost, measured with a holdout — and the arithmetic of how big that holdout has to be.
Camille Laurent · 12 min read
BMI weighs you and divides by your height squared. It cannot tell muscle from fat, which is why lean athletes get classed overweight. FFMI removes the fat first — and inherits every error in the body-fat estimate it is built on.
Aisha Karim · 13 min read