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Turn reps in reserve into a useful training signal.
Convert RIR to resistance-training RPE, compare a completed set with your target effort, and understand what the number can and cannot tell you.
Free to use. No signup. Your inputs stay in this browser.
Calculate your set effort
Use the RIR you estimated immediately after the set.
Everything runs locally. Nothing is saved or transmitted.
RIR to RPE chart
RPE describes the effort of the completed set. RIR describes how many additional repetitions you believe remained before task failure.
No additional repetition was available with the same technique.
You estimate that one more repetition was available.
You estimate that two more repetitions were available.
You estimate that three more repetitions were available.
You estimate that four more repetitions were available.
You estimate that five more repetitions were available.
Use RIR as context, not a verdict
A useful RIR record becomes more informative when the exercise, load, repetitions, technique, and recent history are comparable.
What this calculator can do
- Convert a whole-number RIR estimate to the published RPE scale.
- Compare your actual effort with a planned target.
- Estimate total repetition capacity from completed reps plus reported RIR.
- Give you a consistent language for reviewing comparable sets.
What it cannot do
- Verify how many repetitions were truly available.
- Judge technique, pain, range of motion, or exercise safety.
- Prescribe an exact load increase from RIR alone.
- Replace coaching, clinical advice, or your own judgment.
Research and limitations
The RIR-based RPE scale is useful because it gives lifters an individualized way to report proximity to failure. Its main limitation is also important: people do not estimate remaining repetitions perfectly.
Zourdos and colleagues evaluated the resistance-training-specific scale that maps RPE 10 to 0 RIR, RPE 9 to 1 RIR, and lower RPE values to more repetitions in reserve.
Helms and colleagues describe how the scale can be applied to resistance-training prescription and monitoring.
A scoping review and exploratory meta-analysis found that people were imperfect at estimating proximity to task failure, with accuracy tending to improve closer to failure and at lower repetition counts.
This calculator publishes its full arithmetic: RPE equals 10 minus reported RIR, and estimated repetition capacity equals completed repetitions plus reported RIR. It does not use or reveal Forma’s proprietary progression model. This educational tool is not medical advice.
RIR calculator FAQ
What does RIR mean in lifting?
RIR means repetitions in reserve: how many additional repetitions you estimate you could have completed before task failure.
How do I convert RIR to RPE?
Subtract whole-number RIR from 10. For example, 2 RIR corresponds to RPE 8. This conversion follows the resistance-training-specific RIR-based RPE scale.
Is RIR accurate?
It is an estimate. Research shows meaningful individual error, especially when predictions are made farther from failure or during higher-repetition work. Consistent practice and honest post-set recording can still make RIR useful.
Should every set reach 0 RIR?
No universal RIR target fits every exercise, goal, phase, and lifter. Training to failure can create more acute fatigue and discomfort. Program the target intentionally and review it with performance and recovery.
Does Forma track RIR?
Yes. Forma can keep optional RIR beside load, repetitions, exercise history, weekly muscle volume, nutrition, bodyweight, and steps so you can review effort in context.
Want the full explanation?
The RIR in lifting guide covers the RPE chart, practical use, prediction accuracy, proximity to failure, and primary references.
Want to track the trend?
The progressive overload guide shows how to compare load, repetitions, sets, RIR, and estimated strength across sessions.
Keep RIR beside the set that produced it.
Forma connects effort with your workout history, progressive overload, weekly muscle volume, recovery context, nutrition, bodyweight, and steps.