Methodology

Every figure has a source

The catalog holds 48 entities, 24 people and 37 curated comparisons. Each entity and person record carries the name of the source, a link to the page the figure was read from, the date it was checked, and a note saying exactly what was measured. That source appears wherever the figure appears: in the catalog picker, on the board, and on the entity, person and comparison pages.

People come from official league, club and federation profiles (NBA.com, NFL.com, the WTA, MLS, club sites and the Premier League). Animals come from zoo and museum references such as San Diego Zoo Wildlife Alliance, the Smithsonian and the Field Museum. Sports equipment comes from the sport's own rulebook. Buildings and vehicles come from their operator, manufacturer or a recognised authority such as the CTBUH. Average adult heights come from the CDC's National Health and Nutrition Examination Survey.

Which sources are allowed

Sources are ranked. First the body that owns the number: the league or federation that lists an athlete; the operator or manufacturer of a structure or vehicle; the sport's rulebook for equipment; a standards body such as ISO; a government statistics agency for a population figure.

Where no owner exists — no federation lists a giraffe — a recognised reference institution serves instead: a zoo, a museum, the National Park Service, NOAA, NASA or the CTBUH. Nothing else counts. Encyclopaedias, aggregators and rival comparison tools are not sources, because their figures trace back to nobody who measured anything. Where none can be read, the subject is left out.

What “height” means

Height is not one thing. A giraffe is listed at the top of its head, an elephant and a lion at the shoulder, a dinosaur skeleton at the hip or the top of its mounted frame, a basketball hoop at the rim, a skyscraper at its architectural top. The measurement note on every record says which, and the board draws the figure so that this measured point sits at the stated height. Where an animal's drawing rises above its measured point, a dashed mark shows where the measurement is.

By category: an animal is measured where its source says — top of head, shoulder, or the withers of a horse. A building takes its architectural height, not the height to a mast tip: the Empire State Building is 381 m, not 443.2 m. A vehicle takes the manufacturer's overall height, equipment the rulebook figure, a tree the tallest individual recorded.

Listed athlete heights are what a league or federation publishes. They are not measured by HeightViz and may be rounded or self-reported by the league; the page says which source they came from and when.

Height and length are different measurements

A blue whale, a great white shark, a saltwater crocodile and a tiger are measured along the body by their sources, so those records carry a length, not a height. They are drawn side-on, exactly as long as the shared scale says, and labelled “… long”.

Their vertical extent comes from the artwork's proportions, never from a source, and is never printed as a height. No difference bracket is drawn between a height and a length either, because subtracting one from the other would mean nothing.

Planets

The planets come from one row of NASA's NSSDCA fact sheet — “Diameter (km)”, defined on its notes page as the diameter at the equator — and each is a plain disc exactly that wide on the shared scale. Saturn has no rings drawn: the sourced number is the planet body, and rings would show a width no source gives. The Moon and Pluto sit on the same board because the fact sheet lists them in that table; Pluto is labelled a dwarf planet. Diameters are stored in centimetres and read in kilometres or miles on the planet size comparison.

Centimetres are the only stored value

Every measurement is stored once, in centimetres. Feet and inches, metres, kilometres and miles are ways of printing that one number, worked out when a label is drawn. No second, imperial value exists to drift from the metric one and no rounded copy is kept for display: a height typed as 5'11" is stored as 180.34 cm and reads 5'11" again when shown back.

Conversions use exact definitions — 2.54 cm to the inch, 100 cm to the metre, 160,934.4 cm to the mile, 0.45359237 kg to the pound — and rounding happens in the label, never in the stored value, as the height converter shows. Large values print in a readable unit: metric switches to metres at 10 m and kilometres at 100 km, feet and inches to miles at that same 100 km. The unit changes; the scale does not.

One scale, one ground line

Every subject shares one linear scale from the same ground line, so a subject twice as tall is drawn twice as tall. Rendered size is the centimetre value times one number — the pixels per centimetre of that scene — the same for every subject and every ruler tick, so 180 cm draws exactly 20 per cent taller than 150 cm. Rulers in centimetres and feet describe that same scale; downloads render it at a fixed size.

Wide subjects can need more room across than the board has. Rather than scroll, the board lowers that one pixels-per-centimetre number until everything fits: the scene shrinks, the relationship between subjects does not. Below a floor it keeps full size and scrolls instead.

Widths are illustrative: a silhouette's width comes from the drawing's proportions, not from a sourced width, so only the measured value — the height, or the length — is to scale.

Average heights by country

The 200 country pages use one dataset: the NCD Risk Factor Collaboration's Lancet 2020 study of height trajectories by country, open access under CC BY 4.0 and taken from the study's own data file.

Each figure is the modelled mean height at age 19 — the oldest age the study estimates — for 2019, beside the same estimate for 1985. The published 95% uncertainty interval says how precisely the mean is known, not how much people differ from one another.

These are population estimates from a statistical model, not measurements of any individual and not a survey of adults of every age. Browse them under average height by country.

Growth references for children

The percentile calculator and the growth chart read published tables, not a HeightViz model: the CDC's 2000 growth charts percentile data files, the WHO Child Growth Standards for birth to five years, and the WHO Growth Reference 2007 for five to nineteen. Each gives, per sex and age in months, three numbers — L, M and S — from which percentiles and z-scores follow by the LMS method the references specify. The tables are stored exactly as published.

Between published ages, L, M and S are interpolated linearly, as the references intend. Under 24 months they measure recumbent length and from 24 months standing height, so the tools switch there too — which is why a value can step at that birthday.

None of this is medical advice: a percentile is a position on a published reference. The height predictor likewise applies the American Academy of Pediatrics' mid-parental arithmetic with its stated margin, about four inches either way. What a number means for a child is a question for a clinician.

When sources disagree

Published figures disagree more often than you would expect: a league and a club list an athlete differently, two institutions measure an animal to different points. HeightViz does not average them — an average is a third figure nobody published. The page names the one source it used and the date it was read.

Which figure wins follows the order above, and a better official source replaces a weaker one: figure, source name and check date change together. Where a source gives a range, the note quotes it.

Check dates and corrections

Every entity and person record carries the day its figure was last read, published with the figure rather than kept internally. Re-checking against the same official pages is a standing item on the project's launch checklist, and when a figure is re-checked the date moves with it, so an old date stays visible.

Artwork

Animal silhouettes come from PhyloPic and two landmarks from Wikimedia Commons, under CC0 or CC BY licences, and are credited on the Size Comparison page. Everything else is drawn by HeightViz. No copyrighted photographs or artwork are used; people pages show an initials avatar.

What HeightViz never does

• Invent, estimate or average a height that a source does not state.
• Publish a page whose figures are not sourced; such pages are kept out of search engines.
• Present a length as a height, or a population estimate as a measurement of a person.
• Save the names and heights you type. A shared link carries them in the link itself and nowhere else.
• Generate comparison pages by combining names. Every comparison page is chosen by hand.