Calculator inputs
Enter either a known 1RM or a calibration set. The tool estimates failure reps, RIR, RPE, target load, and effort zone.
Example data table
| Exercise | Load | Completed Reps | Estimated 1RM | Formula | Predicted Failure Reps | RIR | Estimated RPE |
|---|---|---|---|---|---|---|---|
| Back Squat | 120 kg | 5 | 150 kg | Epley | 7.50 | 2.50 | 7.50 |
| Bench Press | 85 kg | 6 | 105 kg | Brzycki | 7.86 | 1.86 | 8.14 |
| Deadlift | 180 kg | 4 | 210 kg | Lombardi | 5.54 | 1.54 | 8.46 |
Formula used
1) Reps in Reserve
RIR = predicted reps to failure − completed reps
2) Estimated RPE
Estimated RPE = 10 − RIR
3) Intensity percentage
Intensity % = (current load ÷ estimated 1RM) × 100
4) 1RM estimation models
Epley: 1RM = load × (1 + reps ÷ 30)
Brzycki: 1RM = load × 36 ÷ (37 − reps)
Lombardi: 1RM = load × reps0.10
5) Target load for planned reps and RIR
Epley: target load = 1RM ÷ (1 + (target reps + target RIR) ÷ 30)
Brzycki: target load = 1RM × (37 − effective reps) ÷ 36
Lombardi: target load = 1RM ÷ effective reps0.10
Effective reps means target reps plus target RIR. Different formulas shift estimates slightly, so keep one method consistent across your program.
How to use this calculator
- Enter the load used in your set and the reps you completed.
- Add either a known 1RM or a calibration set from the same lift.
- Select the formula you use for estimating strength.
- Enter your target RIR for programming the next set.
- Optionally add planned reps, reported RPE, and plate rounding.
- Press Calculate RIR to see effort, target loads, and guidance.
- Download the summary as CSV or PDF for training logs.
Frequently asked questions
1) What does reps in reserve mean?
Reps in reserve estimates how many more clean reps you could have performed before true failure. Lower RIR means harder effort and usually higher fatigue.
2) How is RIR related to RPE?
A common coaching rule is RPE = 10 minus RIR. A set at 2 RIR is roughly RPE 8, while 0 RIR is near RPE 10.
3) Which formula should I choose?
Choose one formula and use it consistently. Epley is common for moderate reps, Brzycki is often used for lower reps, and Lombardi changes more gradually across rep ranges.
4) Why can actual RIR differ from the estimate?
Bar speed, exercise variation, technique breakdown, fatigue, and motivation all affect real effort. Formula estimates are useful guides, but honest set rating still matters.
5) Can I use this for hypertrophy training?
Yes. Many lifters program hypertrophy work around 1 to 4 RIR. That range often balances hard training, quality technique, and recoverable fatigue.
6) Is 0 RIR always best for progress?
Not always. Reaching failure frequently can increase fatigue and reduce performance on later sets. Many programs use near-failure work strategically instead of every session.
7) Should I track RIR for every exercise?
It is most useful on primary lifts and stable accessory movements. Track the exercises where effort accuracy helps load selection and weekly progression decisions.
8) How often should I update my 1RM input?
Update it after meaningful strength changes, after a test week, or when calibration sets clearly drift. A stale 1RM can distort load recommendations.