You really should post this in the figure forum.
If you are talking historical figures, i.e. those figures not corresponding to the scales of military vehicle models (1/72, 1/48, 1/35) there are a variety of sizes. Historicals are generally spoken of in size, not scale, although they do correspond to a scale and busts may be an exception.
A few common sizes for figures: 54mm, 65mm, 70mm, 75mm, 90mm, 120mm (commonly confused with 1/16 scale), 150mm, 200mm, 250mm.
Common bust scales may include: 1/10, 1/8, 1/6, 1/4 (not too common).