How can I convert from one rep range to another?

Question

There are formulas that take how much you can lift at however many reps and convert to a 1 rep max. Are there similar formulas that take the same parameters and calculate how much you can lift at any rep amount?

Or should I just calculate my 1 RM then use %s of it at different rep ranges (for example 10 reps at 75% of my calculated 1RM)?

Answer 1

Here is an algorithm to convert from one rep range to another using Epley formula:

1. Calculate your 1 rep max (1RM) using the formula 1RM = w(1+r/30)
2. Move the formula around to this 1RM/(1+r/30) = w
3. Enter in your known 1RM and the new rep amount you want to use to calculate the weight you should use

(other formulas could be used. Here is wiki with formulas: https://en.wikipedia.org/wiki/One-repetition_maximum)