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This is similar to this question about metric measurements. In Australia, a common measurement is 90mm x 45mm for timber. A 4x2 would be (approx) 100mm x 50mm but, as I understand it, that is the milled rather than final measurement. Does the smaller metric size refer to the final measurement or does have nothing to do with a 4x2?

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Also Why are 2"x4"'s really 1.5"x3.5"? – Niall C. Aug 16 '11 at 20:03
up vote 4 down vote accepted

It's a bit wider than a typical US 2x4, but likely equivalent. A 2x4 that you get for building is 3.5"x1.5" so that would equate to 89x38mm.

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90x35 is also available - that would be closer to the 89x38mm you've quoted above. I dare say 90x45 is more useful since it maintains the 2:1 ratio. – dave Aug 16 '11 at 21:08
In the sense of someone saying "a 2x4 is/isn't strong enough to do that" sure, 90x45 or 90x35 are equivalent. If you're trying to build a box you may need to tweak plans that care precisely how wide a 2x4 is. – Kate Gregory Aug 16 '11 at 21:14

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