How numbers earn their place on this site: the sources we accept, the cross-checks a figure must survive, how disagreements between sources are handled, and how corrections get made.
A length is published on this site only if it comes from a published source with a name on it: a clubmaker's specification sheet, a manufacturer's published specification, the USGA and R&A Equipment Rules, or a fitting chart that circulates in published form and can be pointed to. Blog opinion, forum consensus and 'everyone knows' are not sources. If a figure cannot be traced to a publication, it does not appear — including when that leaves a gap in a table, which is marked as a gap rather than filled with an estimate.
Where two independent sources publish the same datum, we check them against each other before publishing. The standard iron lengths on this site pass that test cell for cell: The GolfWorks' specification sheet and Hireko Golf's chart agree on every men's steel iron, on graphite playing half an inch longer than steel, and on the women's standards sitting one inch lower. Data that rests on a single source is used only when the source is the authority for its own system — a manufacturer's spec for its own clubs, a junior brand's chart for its own sizes — and single-source data is identified as such on the page or in our research notes. One cell of one reproduced chart we use could not be cleanly verified in its only reproduction; it is flagged in the research file rather than silently polished.
Disagreement between good sources is information, and this site shows it rather than averaging it away or quietly choosing. The standing example is the driver: the clubmaker standard is 45 inches, a major manufacturer's fitting guide calls 45¾ inches the standard, and current stock drivers ship between 45½ and 46 inches. The chart page prints all three, with the sources credited at the foot of the page, and explains why they differ. The same rule applies inside the fitting charts: the widely reproduced height-and-wrist-to-floor chart, Hireko's coarser chart and Wishon's wrist-to-floor-only method give slightly different answers at the same measurements, and the site names the system its calculator uses instead of pretending the others do not exist.
Each calculator is tested against its published chart before it goes live: the chart's own rows are fed through the tool and the outputs compared against the printed values, including the edge rows at the top and bottom of each table. A tool that cannot reproduce its own source chart does not ship. When a chart itself contains a known quirk — one widely circulated fitting chart has a wrist-to-floor band that overlaps the row above it — the quirk is printed as published on the chart page, together with the resolution the calculators apply (the height pairing), not silently rewritten into a chart that exists nowhere in print.
Anyone can flag a number through the Report an Error page, linked in the footer of every page, or by email. Reports are checked against the cited published source — not against our own previous output. When a report is right, the figure is corrected, and where the error was ours rather than a source's, the correction is made without editing the record of what the source said. When a source itself changes a specification, the site follows the current published figure at its next verification pass.
The numbers on this site come from the cited publications and from nowhere else. No club manufacturer, shaft maker or retailer selects, sponsors or approves the figures in the charts, and a maker's specification is printed because it is published — including when it disagrees with the number next to it. Commercial relationships, if any are ever added to the site, will be disclosed on this page.