To make construction easier, I try to use stock dimensional ‒ in inches ‒ milled softwood lumber straight as it comes off the rack at the lumber suppliers here is the US. For metric measurements (OK, that’s the rest of the world) you would use stock sizes available in your country. So I thought I would compile a list of stock metric sizes available, but I found that easier said than done since there are variations by region as well as by country. There is also the question of “nominal” size, or what stock sizes are traditionally called, as opposed to the actual dimensions. Below is a chart showing the “nominal” size call outs (what you ask for) used in the US and the actual milled dimensions in inches (the size you get). Then I listed the approximate metric dimensions of the actual milled imperial dimensioned stock that I have used. With this information you should be able to choose the best available equivalent stock lumber to use where you are.

Most designs are flexible enough to accommodate differences in sizes. Use your judgment. Actual measurements such as length dimensions are also flexible. Or do what I have done and get a yourself a tape measure that has both imperial and metric measurements. If you are familiar with Google’s free SketchUp drawing application ‒ that’s what I have used here ‒ you can go to their 3D Warehouse and open up my SketchUp 3D files and convert to metric. You will have to pull off the dimensions yourself. (See my web site or blog intro page for links to Google.) Since my stock sizes are different from what you may be using you will have to make sure the difference doesn’t matter ‒ in most cases it wont. Again, all is flexible.