The 1RM calculators become less accurate with higher reps
because of the differences in muscle fibres, with the following
equations you can obtain a good estimate as long as reps are
not over 12(weight in kg or lbs):
Brzycki equation[1]:
Weight / ( 1.0278 - ( 0.0278 * Number of reps ) )
The alternative equation[2]:
Weight * ( 1 + ( 0.033 * Number of reps ) )
These equations can give you an idea what you may get, for example
in high school when I could bench press 165 lb x 4 reps, my 1 RM
was 185 lb, using the Calculators:
By the Brzycki equation:
165/(1.0278 - (0.0278*4 )) Estimate= 180 lb 1RM
By the alternative equation:
165*(1+( 0.033*4 )) Estimate= 186 lb 1RM
And when I squatted, IIRC back in HS: 225 x 12 reps my
1RM was about 315 lb.
The estimates for you:
Method [1] = 551 lb
Method [2] = 569 lb
The calculators will not be accurate for lifts like DB press because getting
the weight up, here is like half the work. It would be interesting to compare more
maxes with these calculators. The way you train in other lifts may also influence
your 1RM max results.