Load calculator by RPE and RIR
Enter the weight, the reps and how many were left (RIR) to estimate your 1RM and see suggested loads for each rep range.
Estimated 1RM 1RM (one-rep max) 1RM is the heaviest load you can lift for a single repetition with good technique in a given exercise.
80 kg
Suggested loads (aiming for 2 reps in reserve)
| Target reps | Suggested load (RIR 2) |
|---|---|
| 3 reps | 68.6 kg |
| 5 reps | 64.9 kg |
| 8 reps | 60 kg |
| 10 reps | 57.1 kg |
| 12 reps | 54.5 kg |
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Terms used in this calculator
These concepts show up in the math and help you read the result with more context.
- RIR (reps in reserve)
- RIR is the number of repetitions you could still perform when you end a set.
- RPE (rating of perceived exertion)
- RPE is an effort scale where RPE 10 equals failure (0 repetitions in reserve).
- 1RM (one-rep max)
- 1RM is the heaviest load you can lift for a single repetition with good technique in a given exercise.
How RIR becomes load
RIR is how many reps you could still do when you end a set. Adding RIR to the reps completed, we estimate how many reps you'd do to failure — and, from that, your 1RM.
With the estimated 1RM, the calculator suggests loads for different rep ranges, aiming for a safety RIR (around 2), which balances stimulus and recovery.
Adjust for the day's execution
Strength swings with sleep, food and fatigue. Treat the suggested loads as a reference and confirm by the perceived effort on the spot, not as a fixed number.
Logging RPE/RIR across the weeks shows the real trend and helps you decide when to safely add weight.
Sources and references
- Source: Zourdos MC, Klemp A, Dolan C, et al. Novel resistance training-specific rating of perceived exertion scale measuring repetitions in reserve. J Strength Cond Res, 2016. — Journal of Strength and Conditioning Research (PubMed)
Reviewed by the SelfShapeAI research team.
Frequently asked questions
What's the difference between RPE and RIR?
RIR is the number of reps in reserve (how many were left). RPE is the rating of perceived exertion on a scale, where RPE 10 equals 0 RIR (failure). RPE 8 corresponds to about 2 RIR.
Do I need to train to failure to progress?
No. Training with 1 to 3 reps in reserve on most sets tends to balance stimulus and recovery, allowing more quality volume across the week.
Is the load estimate exact?
It's a reference. The calculation uses RIR and 1RM formulas, more accurate at low rep ranges. Always adjust for the day's real execution.
Keep reading
Take the math into your training
SelfShapeAI builds the plan, logs your loads and adjusts volume with context — so you don't have to run the numbers by hand.
