If you enjoy neat categories, here's a practical way I break it down in my head: tiny pieces, medium pieces, and
long reads. Short stories are usually under 7,500 words;
novelettes 7,500–17,500; novellas about 17,500–40,000; and novels anything above 40,000 by the SFWA standard. Still, publishing norms nudge most commercial novels into the 60,000–100,000 range, so the average "book" people buy and shelve tends to be closer to 80k.
When you do the math that means an average novel (say 80k) is around four times the length of a 20k novella. If you compare an 80k novel to a 35k novella, the multiple drops to about 2.3. My takeaway is that there’s no single fixed multiplier, but a useful rule of thumb is: expect novels to be roughly two to five times longer than novellas. That variance comes from genre, authorial voice, and publisher expectations — a cozy mystery will aim for the lower end, while a sprawling fantasy can double or triple the usual
novel length.
I like keeping those ranges in mind when choosing what to read. Sometimes I
crave the intensity of a novella; other times I want the slow burn only a longer book can give, and knowing the typical word counts helps me pick the right mood.