I generally stick to the Fibonnaci sequence (5, 8, 13, 21, 34, 55, 89 etc) when I’m typesetting as a guide for type sizes but I find that it can be restrictive on its own so I’ve made further number sequences which offer a better choice of size.
Size 8 type is a little on the small side for most body copy so to use only the Fibonacci list would cause problems. It’s very simple to work out a type size list that should be well balanced — use root numbers as a multiplier. Root 2, root 3, root 4 etc are all interesting numbers to create well-proportioned sizes and this goes for page measurements as well as type sizes. Root 2, for instance, is what the DIN paper system is based on. The golden ratio is roughly the root of 2.6 so root 2 and root 3 are also good for getting a pleasing balance in type/paper sizes.
The basic point is to make things proportional. The next step is to make sure you’re using a more interesting measurement to use in proportions than, say, 1/2 or 1/3 because these just give predictable results (and are actually called static ratios for this reason).
Golden section lists (multiply each by 1.618 and round to nearest):
3, 5, 8, 13, 21, 34, 55, 89 etc
4, 6, 9, 14, 23, 37, 60, 97, etc
6, 10, 16, 26, 42, 68, 110, etc
Obviously the smaller sizes aren’t as significant because the contrast between them won’t be big at all — the lists are most useful when you’re involving large type with small — and, of course, the bigger the contrast, the better.
Root 2 list ( multiply by 1.414 and round to nearest):
2, 3, 4, 6, 8, 11, 16, 23, 33, 47, 66, 93 etc
If paper of DIN proportions, which is the norm in Europe, is based on root 2 would it not make more sense to use root 2 as a basis for proportions of type sizes and layout also? I’ve been using the golden ratio so far which is slightly more than root 2. I’ll have to try it and find out. To be truly pedantic you could always work to a decimal place or two in the type sizes just to make sure you’re bang on root 2 proportions… Might be a little over-the-top though.