Finding Rep Max

I’ve got a stupid question. I am about to start Chad’s QD training program and I need to find a load that is 18RM for example and use it for 6 sets and 3 reps each. Instead of guess and try on the load, I was wondering if there are a chart that approx. your RM at different weight/rep. Like if your 1RM on bench is 225 then ur 6RM should be around 185…something like that.

Thanks in advance for any help!
G

Look at the bottom

Interesting link reidhoch, thanks.

for 18 rep max:
weight = 0.625 1rm

This is based on Epley formula.
This is only an approximation. If you never lift with 18 reps then you will probably have only a crude approximation. It is good for a first guess.

If you can do some math then you can use the following equations.

1rm = (1 + 0.0333 reps) x weight

reps = [(1rm / weight) - 1] / 0.0333

weight = 1rm / (1 + 0.0333 reps)