`1RM = (100* w )/(48.8+53.8e^(-0.075* r ))`

Enter a value for all fields

The Wathen Max Weight calculator computes the approximate maximum weight one can lift using the Wathen formula.

INSTRUCTIONS: Choose your preferred units and enter the following:

• (w) Weight Lifted in Repetitions.
• (r) Number of Reps.

Max Weight (1RM):  The calculator returns the approximate max weight in pounds.  However, this can be automatically converted to other mass or weight units (e.g. kilograms) via the pull-down menu.

Math / Science

Max Repetition Weight formulas like Wathen are intended to provide an estimate on the maximum weight one can lift without having to attempt such a lift.  The motivation is to avoid injuries associated with lifting one's max.  The Wathen One Max Weight formula is:
 

   1RM =  (100*w) / (48.8 + (53.8*(E**((-1)*0.075*r))) )

where:

• 1RM = One Rep Maximum, the approximate limit that could be lifted once.
• w = weight lifted in multiple repetitions
• r = number of repetitions lifting weight w.

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