Balsa Density, Grain, and Grade

Written by Al and Rod Clark Learn about balsa, grades, densities, grains, and proper applications. Information and tips for any balsa kit, plans, or scratch build project
When you are tackling your next balsa project, spend a few moments to learn about the different densities, grades, and grains of balsa. Not all balsa is created equal and its application depends on the characteristics.

Balsa Density

GradeUltra LightLightLight MediumMediumMedium HardHard
Density in
4-5.45.5-6.0 6.1-7.57.6-9.59.6-1214 +
 |----Contest Grade Balsa----||-------------Non Contest Grade Balsa-------------|
So how do you determine the density and grade of balsa? It is a two step process to determine the various density ranges shown above. First, weigh the sheet of balsa. While there are very accurate electronic scales, I'd suggest you use a small postage scale (the kind with a weight and clip). Once you know the weight of the balsa refer to the nomographs below to determine the density.

Balsa Density Nomographs

After you weight a sheet of balsa the following nomographs are used to identify the balsa density and grade.

Download a complete PDF of all of the nomographs.

Balsa Grains

Builders should take note of the different balsa grains. Each grain type has different characteristics and should be used in different applications. Notice that the C-grain balsa sheet has a mottled appearance and distinct checkerboard pattern. It is very stiff across the sheet and splits easily. It will not easily wrap around curved surfaces without cracking. C-grain is used for sheet balsa wings and tails, flat fuselage sides, wing ribs, formers, and trailing edges. C-grain is usually hard to find in local hobby shops. I mainly use it for sheet tail surfaces. B-grain grain lines are shorter than A-grain and it is less stiff than C-grain. If you look at the narrow edge of the balsa sheet, B-grain will look the same as it does on the wide, flat side. B-grain can go around soft curves without cracking. This grain is used for flat fuselage sides, wing ribs, formers, planking gradual curves, and wing leading edge sheeting. A-grain has long fibers that show up as long grain lines. If you look at the narrow edge of the balsa sheet, A-grain will have a checkerboard appearance. This is the most flexible of all grains, and it is quite easy to wrap around curved surfaces. A-grain is typically used for sheet covering rounded fuselages and wing leading edges, planking fuselages, forming tubes, strong flexible spars, and hand launch glider fuselages. By Al and Rod Clark

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Good information

Nice Article

Agreed. Keep these types of articles coming.

Good Info.



This is great. I've only built kits and occassionally balsa to replace a broken piece. I just looked for any sheets that didn't look cracked. No idea about the grain and density. Thanks.

I printed this article from the website. Good information.

This is probably a better method than what I did before which was playing ine-mine-moe.

I love the looks of the charts presented here. Perhaps someone could have a look at the link to the .pdf as it's broken.

Stan, Thank you for letting us know! We have corrected the issue and the PDFs are available for download again.

what i need is c-grade balsa wood

Handy, but the balsa density ranges are different to those shown in other charts such a Sig etc. Which ones are correct? Who knows?


contest balsa wood is on the decline this is due to the production of windmills around the world, as wind mills now use balsa wood for sheeting due to its light weight. this is the main reason of shortage of balsawood. hope this helps

So as presented, it appears that the contest grade range is on the harder (and denser?) end of the balsa scale. Too bad most (the few that have any) stores which carry balsa have only what appears to be grade A leaving us with only the weaker varieties. The best supply I've seen in a while is at Hobby Lobby. Michaels was divesting itself of balsa as of a year or two ago at least the branch near me at the time in Connecticut. I haven't been to a Michaels in my new Tennessee location yet. A Hobbytown is nearby but I don't recall seeing balsa there. That's it for me for many miles around from here. Sigh.

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