What is an estimated 1RM?
An estimated 1RM predicts your max from a completed set without requiring a true max attempt.
A one-rep max, or 1RM, is the most weight you can lift for one good rep. Testing it directly can be useful, but it is also stressful and not something most people should do every week. An estimated 1RM predicts that max from a normal completed set.
The classic Epley formula is simple: weight x (1 + reps / 30). If you lift 100 kg for 5 reps, the estimate is 100 x (1 + 5 / 30), or about 116.7 kg. It is an estimate, not a guarantee.
How RPE refines the estimate
A set of 5 at RPE 10 and a set of 5 at RPE 7 should not mean the same thing. The RPE 7 set had reps left, so it suggests you could have done more than 5. That is where RPE-adjusted estimation becomes more useful than reps alone.
JustGains uses an RPE-adjusted Epley approach. In plain terms, it adds the reps you probably had left to the reps you actually did, then applies the Epley style estimate. A set without RPE still gets a baseline assumption so it can produce an estimate, but logged RPE makes the estimate more personal.
| Example | Interpretation |
|---|---|
| 100 kg x 5 @ RPE 10 | About 116.7 kg using the 5 completed reps. |
| 100 kg x 5 @ RPE 8 | Adds about 2 effective reps before estimating. |
| 100 kg x 1 @ RPE 10 | The estimate is the weight itself. |
Estimated maxes are best used as trends. If your estimated bench rises from 100 to 110 over a training block, that probably means your strength moved. The exact number may be a little high or low depending on exercise, rep range, technique, and how honestly RPE was logged.
Use calculators for quick checks: bench 1RM, squat 1RM, and deadlift 1RM. Then use training logs to watch whether the estimate actually improves over time.
FAQ
Keep learning
What is RPE?
RPE is a 1 to 10 effort scale that helps you log how hard a set actually felt.
RPE vs RIR
RPE and RIR describe the same idea from opposite sides: effort versus reps left.
What is progressive overload?
Progressive overload means giving your body a little more challenge over time.