[DesertRatTom]

The rest of the world is on the metric system, so no point in manufacturing in imperial as well. Having to reset the machinery that peels, handles, stacks, glues and compresses sheets of ply is fraught with waste and costs. We just have to adapt because imperial fans are a nearly insignificant minority now and the differences are minescule.

I recently found this chart of standards for plywood types and grades. I really use a lot of A-B grade for my projects.

 

[DesertRatTom]

1) That is no excuse since a lot is manufactured for the US market.
2) But even if they produce by the metric system, they could say it’s 5mm, or 18mm thick. I’m more annoyed by the fact that it’s advertised (and sold) in fractions of inches, when in reality it’s not.
So, when you buy a sheet of plywood you can’t really tell what will you get (in terms of thickness, number of ply, and what the inner layers are made of). The only way is from previous experience.

Imperial sizes are no longer a world standard. We're about the only place left using imperial sizes.

I see using the imperial sizes as a convenience. Massive quantities of metric sized ply is imported to the US. I'm not sure if there is any manufacturer in the USA producing ply. And if they hope to sell it overseas, they will have to produce metric.

Not sure it matters much so long as the makers identify it by its metric size. Calling 18mm 3/4 inch is something done in ad copy and price tags. I don't think there's anything to be done about it. I mean, if you want to use plywood, you don't have any alternatives anymore.

 

[DesertRatTom]

I would also like to add, that no plywood is exactly the thickness advertised. A little moisture, or dryness and the dimension will change. That's why we have to buy or make exact fit jigs to cut dados and grooves rather than just buying one or two router bits or fixed with dado sets.

My big issue with metric is that I grew up imperial and I know what a 4x4 should be, but a 100 mm measure is something I have to think about for a few seconds. And how long is a meter? That isn't instinctive to me. A little over a yard, three feet and a nuggie? But my complaints have as much influence as a fart in a hurricane.

 

[DesertRatTom]

You’re right. Anyway, I read somewhere that plywood made to the full size of 1/4”, 1/2”, etc can be purchased. Do you know about such products?

Never found any in the usual places, but I bet you can find a big lumber supplier who will have it or can order it. I live in the desert now, and my supplier is an hour's drive away, and so far as I know, they only have Baltic Birch ply in metric, 5x5 feet square.

l think 2x and 4x is actually 1 5/8ths and 3 5/8ths, which is to say 41.28mm and 92.58mm. To confuse us all even further, lumber is sold by the board foot, which is 12 inches square by one inch deep. Don't know how they sell it in metric countries, but the metric equivalent is 304.88 mm square, by 24.50mm.

Out in the shop I have a mesuring stick that's one meter long, with both metric and Imperial numbers on the same face, so I can, if needed, just look and see how long a metric measure is in inches and feet. I do think metric is easier in most ways, but I can't visualize a meter and think of it as a "fat" yard.

I found this on the web. It's a conversion chart. Detailed down to 32nds of an inch.