I have finally found a simple equation to help you calculate your 1 rep max (1RM) without having to put your anatomy and joints in danger. This equation was developed by researchers at the University of Mexico (albuquerque), to calculate your 1RM on the bench press with 99% accuracy.
All you need to know is your 5RM, which is the weight that you can lift for 5 total reps without any assistance from a spotter. A safe way to figure out your 5 RM is to do three warm up sets of 5 reps and increase your weight about 15-20% each set until you’re ready to do your 5RM at 95-100%. Here’s a gross example:
135 lbs for 5 reps – warm up at about 50% effort
160 lbs for 5 reps – warm up at about 70% effort
190 lbs for 5 reps – warm up at about 90% effort
200 lbs for 5 reps – 95% effort. Consider this your 5RM.
Here’s the formula:
(5RM weight x 1.1307) + 0.6998
So if your 5RM is 200 lbs, the 1RM math will look like this:
(200 x 1.1307) + 0.6998 = 226
Your 1RM is 226 lbs.
Want to figure out your working weights at 20%, 40%, 60%, 80% or other percentages, just multiply 226 by 0.2, 0.4 or the percentage you wish to lift for that set.
This formula was conducted using the bench press but it should be fairly accurate for determining your 1RM in other big lifts too.
Post your 1RM for your bench press below!