Vasa · 1628
The Vasa: two feet in one hull, one of 11 inches and one of 12
Four carpenters' rules were recovered from the wreck, all slightly different. Two were marked in Swedish feet of twelve inches, two in Amsterdam feet of eleven. Every one of them was used correctly.
On 10 August 1628(Verified) the Swedish warship Vasa left Stockholm on its first voyage and sank within about twenty minutes of setting sail(Verified) , in front of the crowd that had come to watch it go.
The cold, low-oxygen water of the Baltic preserved the wood. When the ship was recovered it was almost entirely intact, which means the evidence was intact as well. It is held by the Vasa Museum in Stockholm, where Fred Hocker, the museum’s head of research, measured the timbers.
Inside the wreck he found four carpenters’ rules, all slightly different lengths(Verified) .
Two systems, both correct
Two of the rules were marked in Swedish feet, divided into twelve inches. Two were marked in Amsterdam feet, divided into eleven.(Verified)Both divisions were standard. Neither was a mistake. A Dutch shipwright working to a Dutch rule and a Swedish shipwright working to a Swedish rule were each measuring accurately, in a shipyard that employed both.
The millimetre values below come from one source only, and that matters enough to say before quoting them. The Amsterdam foot is 283 mm and the Swedish foot is 297 mm.(Single source: Tim Harford) The second newsroom that reports the rules gives no millimetre figures at all.
The shorter foot has the longer inch
That pairing is the part worth slowing down for, because the intuition runs the other way.
Shorter foot, longer inch. A carpenter who called out nine inches from an Amsterdam rule and a carpenter who called out nine inches from a Swedish one were describing timber that differed by this much.
Divide 283 by 11 and divide 297 by 12. The foot that is 14 mm shorter is divided into fewer parts, so each of its parts is nearly a millimetre longer. Millimetre values from a single source.
Source: Tim Harford, reporting Fred Hocker's measurements
So the word “inch” did not mean one thing in that shipyard, and neither did the word “foot”, and the two errors do not point the same way. A shipwright asked for a longer foot got a shorter inch with it.
A ship is built from both sides at once
That is what makes this different from a drawing with a wrong number on it. A drawing can be checked against itself. A hull under construction is checked against the other half of the hull, and the other half was being built by someone holding a different rule.
The Vasa is more asymmetric than most ships of its day, with more structure on the port side than the starboard side, and it leaned to port.(Verified) On 10 August 1628 a gust caught it, and it kept leaning.
The Mars Climate Orbiter had a version of the same problem 371 years later: a solar panel mounted off-centre, and nine months spent correcting the twist that caused. A body built lopsided never stops asking to be straightened. Both were undone by the correcting rather than by the building.
Where the sources actually stand
Two separate organisations report the four rules, which under the method used here is the standard. There is a caveat, and it belongs in the article rather than in a footnote: both of them are reporting the work of one researcher. Fred Hocker measured the ship, and everything downstream is his measurement.
That is normal for an archaeological finding and it is acceptable. It is not the same thing as two organisations independently establishing a fact, so he is named rather than presented as consensus.
The third source listed below was retrieved specifically to test the four-rules claim, and does not contain it. It supports the twenty minutes and nothing else. Recording that is the point of keeping a source list rather than a bibliography.
The last case is the one where somebody did check.
Cut register
Figures that circulate and are not published here
- 1,300 m SINGLE-SOURCE Traced to a search summary and never confirmed at a source. A summary that says a distance exists is not a record of the distance.
Sources
3 entries · 3 independent organisations
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S01
Tim Harford SECONDARY
Reports the four rules, the two systems of feet, and the hull asymmetry. The only retrieved source that gives the feet in millimetres. Attributes the finding to Fred Hocker of the Vasa Museum.
Accessed 11 September 2026
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S02
The World (PRX) SECONDARY
New Clues Emerge in Centuries-Old Swedish Shipwreck
Independent newsroom reporting the same finding: four rules, Swedish feet of twelve inches, Amsterdam feet of eleven, and more structure on the port side. Gives no millimetre values.
Accessed 11 September 2026
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S03
Smithsonian Magazine SECONDARY
Supports the sinking within about twenty minutes. Retrieved specifically to test the four-rules claim and does not contain it. Listed here to record the negative result.
Accessed 11 September 2026