One-Rep Max
Predict 1RM from a working set
| % 1RM | Weight | Reps possible |
|---|---|---|
Important — please read
These are estimates — they are not safe targets. Heavy attempts at a maximum lift can cause serious injury (back, knees, shoulders, pec tears). Never attempt a true 1RM without proper warm-up, perfect form, and a competent spotter or safety bars. If in doubt, use a 3-5RM submax test instead.
About One-Rep Max
A 1RM (one-rep max) calculator estimates the heaviest weight you could lift for a single rep, based on a set you actually completed. Trains and competitions program weights as percentages of 1RM — knowing your 1RM lets you pick the right load without having to test-max every session.
Frequently asked questions
Brzycki, Epley, Lander — all close. Brzycki is the default; loose consensus is to average a few formulas.
1RM formulas are accurate up to ~10 reps. Beyond that, the estimate drifts low because fatigue compounds non-linearly.
Strength athletes do, with experienced spotters and warm-up sets. For most lifters, the estimate is safer and accurate enough.
Beginners can add 5-10 lb per week on big lifts. Intermediate: 5-10 lb per month. Advanced: 5-10 lb per year.
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One-Rep Max
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