Over the years a number of people have produced formulae for calculating an approximate 1RM; based on reps and weight used. Whilst studies seem to favour the Epley formula over the others (in terms of accuracy), I have a few alternatives here.
Brzycki equation :
1RM = Weight / ( 1.0278 - (0.0278 x number of repetitions ))
This formula first appeared in a paper entitled Strength testing: Predicting a 1-rep max from reps-to-fatigue in a 1993 issue of the Journal of Health, Physical Education, Recreation and Dance.
Epley equation :
%1RM = 1 / (1 + (0.0333 x number of repetitions ))
Presented by Boyd Epley in 1985.
Lander formula :
1RM = weight / (1.013 - (0.0267123 x number of repetitions ))
This was presented in a paper entitled Maximums based on reps by J. Lander in a 1985 National Strength Conditioning Journal.
Over to you. Do you use any of these methods yourself, and what have been your own experiences?