1 Rep Max Calculator
Enter a recent working set and get your estimated one-rep max from the Epley and Brzycki formulas, side by side, plus a percent-of-1RM table with weights rounded to plate math.
Members: the Phorme app recalculates this automatically as you log.
Two formulas, one honest answer.
The Epley formula (Boyd Epley, 1985) estimates your max as weight x (1 + reps / 30). It is the most widely cited estimator in strength literature and behaves well across the 2 to 10 rep range that most working sets live in.
The Brzycki formula (Matt Brzycki, 1993) computes weight x 36 / (37 minus reps). The two agree almost exactly on low-rep sets, then diverge as reps climb, with Epley reading higher. Showing both, plus their average, tells you how much to trust the estimate: a wide spread means your set was far from a single.
The percentage table runs off the averaged estimate and rounds every load to the nearest 2.5, so the numbers map onto real plates. Strength work of 1 to 5 reps generally lives at 85 percent and above; hypertrophy sets of 6 to 12 sit between 65 and 85 percent.
- 1. Enter the weight and reps from a recent hard set, ideally 2 to 6 reps taken close to failure.
- 2. Press Calculate to get Epley and Brzycki estimates and their average.
- 3. Read the percentage table to pick loads for any target rep range.
- 4. Recalculate every few weeks from fresh sets; an old max programs stale weights.
Epley: 1RM = weight x (1 + reps / 30) (Epley, 1985).
Brzycki: 1RM = weight x 36 / (37 minus reps) (Brzycki, 1993).
Loading table: Percent of the averaged 1RM, rounded to the nearest 2.5 for plate math.
Questions we hear a lot.
How do the Epley and Brzycki formulas differ?
Epley computes weight x (1 + reps / 30). Brzycki computes weight x 36 / (37 minus reps). They agree closely through about 5 reps, then Epley reads higher as reps climb. We show both so you see the spread instead of trusting a single number.
How many reps make a reliable estimate?
Sets of 2 to 6 predict best. Past 10 reps the relationship between reps and load bends toward muscular endurance, and either formula can miss by 10 percent or more. Use a recent heavy set, not an all-time high-rep grinder.
Should I ever test an actual 1RM?
Only when the number itself matters, such as a meet or a planned testing block. For everyday programming the estimate is close enough, and true singles carry fatigue and technique costs that a hard set of five does not.
Why is my calculated max different between exercises?
Rep-to-max ratios vary by lift and by lifter. Twenty reps on a leg press and twenty on a deadlift are different endurance tasks. Calibrate per lift: if the formula says 300 but 285 moves like a limit single, trust your own data.
How do I use the percentage table?
Match the percentage to your target rep range: roughly 85 percent and up for strength work of 1 to 5 reps, 65 to 85 percent for hypertrophy sets of 6 to 12. Weights are rounded to the nearest 2.5 so they load on a standard bar.
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