Is it possible to estimate (or calculate), in advance, the range of focal lengths you might need for shooting in a given scenario?

For instance, suppose you will be going to the zoo (with your APS-C DSLR) and you want to pack light, and assuming that you will be between 30ft(10m) and 60ft(20m) from your subjects, is it possible to calculate which zoom lens(es) to take to cover this range so that you can get wide angle to reasonable close-ups?

Is there a forumla (or rule-of-thumb estimatation method) that you can use?