What are the ideal sizes for new custom textures?

I want to create some new textures, but I don't want them to look too big or too small in-game.

So when creating them, how can I prevent them from looking huge or tiny? Is their some way to limit the drawing area to the same size as the vanilla Doom textures?

I'm not sure what you mean. A texture made up of 32x64 panels will be usable in the same way as METAL2, a texture made up of 64x64 panels will be usable in the same way as the GRAY* square panels, and so on. Most textures in Doom are 128 units tall, but in most modern source ports you can use taller sizes nowadays, and of course a single texture can be made up of multiple panels for slight variations (i.e. METAL2 is a 64x128 texture, considering of four similar-looking 32x64 panels). The desired scale of your textures should be pretty easy to get the hang of just from comparing them against Doom's own textures, and the heights and widths of structures in your own maps or others' maps.

It's also worth noting that texture widths should be powers of 2 (8, 16, 32, 64, 128, 256, 512, 1024, 2048, etc), and not weird arbitrary widths, or nearly all sourceports will have difficulty drawing them and will usually just crop them to the next smallest width (i.e. if it's 24 wide, most ports will only draw the first 16 columns).

You also have to make sure it's has a correct height: http://doom.wikia.com/wiki/Tutti-frutti_effect

boris said:

You also have to make sure it's has a correct height: http://doom.wikia.com/wiki/Tutti-frutti_effect

Depends on the source port he's mapping for. If vanilla, it should be 128 units tall. If ZDoom, it should be a power of 2. If Boom or a derivative, it should be able to vertically tile no matter what its height.

You could just look up the dimensions of the existing doom textures and resize whatever textures you have to match it?

64x128
128x128
256x128 (big wide textures)

That probably covers 90% of the textures in Doom.

Don't forget the standard personnel Doom doors and switch panels, which are 64x72 for some reason.

printz said:

Don't forget the standard personnel Doom doors and switch panels, which are 64x72 for some reason.

Many of the floor-to-ceiling heights were 72 in Knee Deep in the Dead. You'll notice that startan styled textures fit really well on walls with a front height of 72.

printz said:

Don't forget the standard personnel Doom doors and switch panels, which are 64x72 for some reason.

Don't waste potential like Doom.wad did with a lot of them, though: make the actual textures 128 tall and use the remaining 56 units to make another, shorter variant to go along with the 72-tall one :)

All of your feedback has been very useful, thanks :)

What's interesting in that early versions of Doom, many textures were 56, 72, and 104 tall. 128 was considered really tall (according to the patch/texture names). I guess they decided to go for a less claustrophobic atmosphere and rearranged the patches/textures to form textures mostly of 128 height.