RIR Calculator — Reps in Reserve

Reps in reserve is how many repetitions you could still have done when you ended the set. It is the simplest way to prescribe intensity without a tested max — you rate the set, and the load follows. Enter the weight, the reps completed and the RIR you felt. The weight field is metric, so 220 lb goes in as 100 kg.

What the calculator does with your rating

Your reps in reserve plus the reps you completed equals reps to failure. That total goes into the Epley formula, 1RM ≈ weight × (1 + reps ÷ 30).

Worked out: 220 lb (100 kg) for 8 reps at RIR 2 means 10 effective reps, so the estimated max is 100 × (1 + 10 ÷ 30) = 133.3 kg, about 294 lb — and the set itself sat at 75% of that max. Cross-check it against the NSCA load chart, which also puts a 10-rep max at 75% of 1RM. Two different traditions, the same answer.

Why rate the set instead of following a number

A prescription written in pounds assumes today is an average day. It is not. Sleep, stress, nutrition and residual fatigue from the last session all move what you can lift, and a max measured months ago may not describe you now — the reviewers of this method point out that a 1RM is unstable in newer lifters and can be suppressed by fatigue carried over from a previous block.

RIR sidesteps the problem by moving the target from the load to the effort. On a bad day you use less weight and still finish two reps short of failure; on a good day you use more. The stimulus stays where you planned it.

How accurate the rating is

It depends on who is rating and how close the set was to failure. Comparing experienced and novice squatters, Zourdos and colleagues found the experienced group rated a genuine single at 9.80 ± 0.18 on the scale, while novices averaged 8.96 ± 0.43. Rating precision also improved as the load rose: the standard deviation of scores for singles at 100, 90, 75 and 60% of max was 0.32, 0.92, 0.97 and 1.18 respectively. Ratings taken far from failure are guesses; ratings taken near it are close to measurements.

The practical consequence for a newer lifter is to record RIR alongside your training for a while before letting it choose loads. A cheap calibration test: stop a set at the RIR you believe you are at, rest briefly, then take the same load to actual failure and count what was really left.

Read next

• Reps in reserve scale — what each number on the published scale means
• RIR vs RPE — two names for the same measurement, counted in opposite directions
• How to use reps in reserve — turning a rating into a load change
• RPE to percentage chart — from effort to a share of your max

This content is informational and does not replace coaching, especially if you are new to training close to failure.