RPE to Weight Calculator Formula

Understand the math behind the rpe to weight calculator. Each variable explained with a worked example.

Use the RPE to Weight Calculator

Formulas Used

Working Weight

working_weight = round(one_rm * pct_1rm / 100 / 5) * 5

% of 1RM

percentage = round(pct_1rm * 10) / 10

Reps in Reserve

rir = reps_in_reserve

Could Do Total Reps

could_do_total = effective_reps

Variables

VariableDescriptionDefault
one_rmEstimated 1RM(lbs)315
target_repsTarget Reps5
target_rpeTarget RPE8
reps_in_reserveDerived value= 10 - target_rpecalculated
effective_repsDerived value= target_reps + reps_in_reservecalculated
pct_1rmDerived value= 100 / (1 + effective_reps / 30)calculated

How It Works

How RPE Translates to Weight

RPE (Rate of Perceived Exertion) uses a 1-10 scale where 10 means maximum effort (no reps left) and lower numbers mean more reps in reserve.

Formula

Reps in Reserve = 10 - RPE

Effective Max Reps = Target Reps + Reps in Reserve

% 1RM = 100 / (1 + Effective Reps / 30)

This reverse-engineers the Epley formula to find the appropriate percentage of 1RM.

Example

RPE 8 at 5 reps means you could do 7 total reps (2 in reserve), which corresponds to roughly 81% of 1RM.

Worked Example

Deadlift 1RM is 315 lbs. Target: 5 reps at RPE 8.

one_rm = 315target_reps = 5target_rpe = 8
  1. 01Reps in reserve = 10 - 8 = 2
  2. 02Effective reps = 5 + 2 = 7
  3. 03% 1RM = 100 / (1 + 7/30) = 100 / 1.233 = 81.1%
  4. 04Working weight = 315 * 0.811 = 255.4, rounded to 255 lbs

Ready to run the numbers?

Open RPE to Weight Calculator