How we source every number
Every number on Woodworking Math says where it came from. Three independent sources is the goal; fewer is shown only with a label that says exactly what stands behind it, and none is never shown.
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The tiers
A figure starts as each publisher's own number. How many independent publishers print it decides what the page shows. The tag in the right column is the one you see under results across the site: three marks for the strongest support, fewer for less.
| Sources | What the page shows | The tag |
|---|---|---|
| 3 or more | The median of their recommended values, and the span they cover. One outlier can't drag a median. | Median of 4 sources |
| 2 | Both values as a range, with both publishers named. More than twice apart, they are not averaged: the page starts at the lower and says they disagree. | Only two sources publish this: Source A and Source B |
| 1 | Only when that source is the authority: the standard itself, or the maker of that exact product. The tag names its role. | One source: Source A, the maker of that product |
| A rule of thumb | Some shop rules were never measured (a tenon a third as thick as the stock, a 1:8 dovetail slope). They are tradition, so the page says so and names the two or more references that state the rule. It is never shown as a median. | Traditional rule, stated by Source A and Source B |
| None | No number. The calculator says the sources are not there yet. | No answer |
What counts as a source
A source is a publisher, not a document. Two data sheets from the same company count once, and a site that copies another's table row for row counts once. We prefer makers' own published data and recognised standards, and we record when each one was read, so a figure can be checked again when the publisher revises it.
Why we refuse instead of guessing
A guessed number looks exactly like a sourced one, and people act on numbers. When the sources are not there, the honest answer is that we don't know yet, so the page says so and the gap goes on our list to research.
How the reasoning is built
Under each result, "Why these numbers?" walks from your inputs to the number: the situation, what it means, the choice it leads to, and the arithmetic. Each step carries the same tag as the numbers. A claim that fails the same source rule is left out, not hedged. Arithmetic is marked as exact by definition, and a step that only restates what you entered says so.