1RM and working load calculator
Enter a recent, real set: the load, the reps you did, and what you had left in reserve. The tool estimates your 1RM, then turns it into working loads for your next sessions.
RIR 0: failure, no extra rep possible. RIR 2: you could have done 2 more. RPE equivalence: RPE 10 = RIR 0, RPE 8 = RIR 2.
Why knowing your 1RM matters
Your 1RM (one-rep max) is the load you can lift exactly once on an exercise. Strength programs are written as percentages of that number: working at 80% of 1RM for 5 reps does not have the same effect as 60% for 12. Without an estimate of your max, those instructions stay abstract and you load the bar by guesswork.
Yet testing your true 1RM on a bar is unnecessary for most lifters: it’s tiring, technically demanding and risky without a spotter. Estimating from a submaximal set gives you a usable number without exposing your shoulders or your back on an average day.
Why reps in reserve (RIR) change the math
A set of 8 reps stopped with 2 reps in reserve represents the same effort as a set of 10 to failure. Ignoring the reserve means underestimating your max, then underloading every session that follows. That’s why our programs prescribe every set with an RIR: the calculator applies exactly the same logic in reverse.
How accurate is the estimate?
Within a few kilos up to 10 effective reps, the Epley estimate is more than enough to set your working loads. Beyond 12, the margin of error grows: prefer a heavier set as your starting point.
RPE or RIR, which should you use?
The two scales say the same thing in opposite directions: RPE 10 = RIR 0 (failure), RPE 8 = RIR 2 (two reps in reserve). Our programs use RIR because it’s easier to count at the end of a set.
Should you test your true 1RM on the bar?
Unless you compete in a strength sport, no. A real test costs a session, demands flawless technique and a spotter, and the number moves with your form on the day. An estimate from a set of 3 to 6 reps gives you a sufficient working baseline.
How often should you recalculate?
At every block change, every 4 to 6 weeks: if your sets get easier at the same weight, your estimated 1RM has gone up and your working loads should follow.
Accurate loads still need a plan
Every program prescribes the sets, the reps and the RIR session after session: all that’s left is loading the bar. The calculator does the rest.
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