Shelf Thickness Question

[Dennis Putnam]

I'm making some shelves and need some help determine the type of wood and thickness so it won't sag in a year or two. It won't be holding a lot of weight but I want to prepare for the worst case (I don't mean 40" CRT TV but perhaps a DVR and/or DVD player). The length will be a little over 4' between supports and will be painted so I'm not worried about grain quality. I was thinking about using whiteboard but I'm not sure 1" stock will be sufficient. I don't know that I can get 4/4 locally very easily. I don't think I want to use plywood because I don't like the look of any of the edge finishing options. In any case what is the rule of thumb for shelf thickness with respect to wood type? Thanks.

[Charles Wiggins]

Use the Sagulator:
http://www.finewoodworking.com/SkillsAndTechniques/SkillsAndTechniquesArticle.aspx?id=28101

[Dennis Putnam]

Cool! Thanks.

[Frank Drew]

As you're using the term here, what's "whiteboard"?

You could reinforce a shelf by screwing a piece of angle iron onto the back edge.

In any case, in addition to added strength, I think thicker shelves (within reason) look better than thin ones; although 3/4" might work for a light duty shelving, it often looks just too dinky.

[David Cefai]

DVD players can get quite warm, which could contribute to warping, so I suggest overengineering the shelves.

[Dennis Putnam]

Thanks. I found some 5/4 white pine at a box store and according the Sagulator that will be ample, although it looks kind of bulky. However, if I put an Ogee edge on it I think it will be fine. Thoughts?