I went ahead and tested my shoulder press today using 115 lbs expecting a possibility of 14 reps due to having 14 reps of 30lbs doing Incline Front Raises (IFR) left / weakest side. There was a couple week gap in between that consisted of a lifting break and a day of the skull-crushers exercise.
Theoretical Calculations
Using this link, https://strengthlevel.com/strength-standards, I compared seated dumbbell press and the standing barbell press. I only looked at the Advanced and Elite section at 170lbs and simply divided the barbell press by the seated dumbbell press and form a range. Ratio = Barbell Press / Seated Dumbbell Press. Advanced Ratio was 1.915 and Elite ratio was 1.846; midpoint ratio would be 1.88.
From the previous blog, the formula between IFR and Seated Dumbbell Press (one hand) was: Seated Dumbbell Press = IFR * 2. Since the seated dumbbell press (two handed) is slightly larger than the barbell press, there will be a theoretical formula between Barbell Shoulder Press and IFR. A formula would go like this:
IFR * (DB Press / IFR) * (Shoulder Press / DB Press) = estimated shoulder press.
Examples
Advanced: 30lbs * (2) * (1.915) = 114.9
Elite: 30lbs * (2) * (1.846) = 110.76
Because my strength to almost to advanced, it would be safe to assume that 115lb shoulder press would be a possible equivalent to my 30lbs IFR given the same rep range. The theoretical ratio would be: 3.833 from (115 / 30). Elite would be 3.7 and these two lifts should be retested once I get at or very close to the Elite category.
The findings
As you can see in the above two images, I had the same 14 reps from my Incline Front Raises to my Barbell Shoulder Press and confirmed my aforementioned formula of 3.83 ratio. This formula was based on my weaker side of my Incline Front Raises of 14 reps compared to my stronger side of 25 reps proving that you’re only as strong as the weakest muscle of the lift and that apparently includes a muscle imbalance. Once I get close to Elite, I will retest to formula to see if it’s still 3.83 or more like 3.7.
To switch between Seated Dumbbell Press and Barbell Press I’m going to setup another equation:
Dumbbell Press * (IFR/Dumbbell Press) * (Barbell Press / IFR) = (.5) (3.83) = 1.915
Formulas
Barbell Shoulder Press = 3.83 * Incline Front Raises
Barbell Shoulder Press = Dumbbell Press (weakest hand) * 1.915
Dumbbell Press (weakest) = Barbell Shoulder Press * .522
Incline Front Raises = Barbell Shoulder Press * .261