# What is the best 1 RM prediction formula

I want to predict 1RM using a formula but I am not sure which is the best to use for the male athletes ages rages from 18 to 30 years old. For example, if I can bench press 80kg 4 times what could my 1RM be?

• There is missing information here. What information DO you know? Obviously, there are different formulae given different pieces of information. For instance, do you know their 3RM, 5RM, 8RM? If you're just trying to find someone's 1RM given their age, there is absolutely no way to generalize that.
– Alec
Feb 22 '16 at 12:06
• What I mean is that if I can bench press 80kg 4 times what could my 1RM be? Feb 22 '16 at 12:10

There are many different formulae for calculating one's 1RM.

I'll list some of the easiest-to-use ones. They'll all use two single variables;

w = the weight used for testing, measured in kilograms (kg)

r = the number of repetitions managed by the athlete at

# Lombardi

Example

Let's say I can do 4 reps at 80kg, my expected one-rep max would be

I feel comfortable with rounding to nearest integer here, because of the overall inaccuracy of any such formula.

# Epley

Example

Let's use the same example, from your comment. With 4 repetitions at 80kg, my expected one-rep max would be

# More formulae

There's a list of these at the One-repetition maximum article on Wikipedia.

# Which is best?

Quite frankly, there is no way of telling, simply because of the diversity of people. One formula might be best for me, but for you, it might be a different one. But I think if you try them all, they should all land pretty close to each other.

In these dealings, there will always be inaccuracies. You can't rely on any such formula to give you anything too precise, so the whole "which is more precise" question seems unanswerable.