One Rep Max Calculator

• Epley (1985) uses a linear relationship: 1RM = w × (1 + reps/30). Every additional rep adds about 3.3% of the weight to the max estimate.
• Brzycki (1993) uses a hyperbolic fit: 1RM = w × 36 / (37 - reps), which caps sensibly as reps climb.
• Lombardi uses a power-law: 1RM = w × reps^0.10, which is gentle at low rep counts and most accurate for 1-5 reps.

All three formulas were fit to real powerlifting data and agree within about 5% for sets of 3-8.

Most strength programs prescribe work as a percentage of 1RM. General guidelines:

• 60% = easy technique / speed work
• 65-75% = hypertrophy (8-12 reps)
• 80% = strength endurance (5-6 reps)
• 85-90% = classic strength (3-5 reps)
• 92-97% = peak power (singles and doubles)

Knowing your current 1RM lets you program intelligently instead of guessing — and this calculator's percentage chart does the math for every band automatically.

Your one-rep max (1RM) is the heaviest weight you can lift once, usually estimated from a set to near-failure rather than tested directly.

The Epley formula is 1RM = weight × (1 + reps/30); the Brzycki is 1RM = weight × 36/(37 − reps). Lifting 100 kg for 5 reps estimates about 116.7 kg by Epley and 112.5 kg by Brzycki.

The NSCA notes these estimates are most accurate at lower rep counts. This calculator applies several formulas so you can compare.

Several validated equations estimate 1RM from a submaximal set. Epley (1 + reps/30) and Brzycki (36/(37 − reps)) give very similar results at low reps and diverge slightly as reps rise; Lombardi uses weight × reps^0.10.

None is universally 'best' — they were derived from different populations.

The NSCA and strength researchers treat them as interchangeable within a few percent for sets under about 10 reps, which is why comparing formulas is useful.

Directly testing a true 1RM carries injury risk and heavy fatigue, and requires spotters and full readiness.

Estimating from a 3-8 rep set is far safer and repeatable, which is why the NSCA and most coaches program from estimated maxes. Estimation also lets you gauge strength without a max-effort day.

The trade-off is a small accuracy loss that grows with higher rep counts, so keep the test set relatively heavy.

Strength programs prescribe load as a percentage of 1RM:

• roughly 85-100% for strength (1-5 reps)
• 67-85% for hypertrophy (6-12 reps)
• below 67% for endurance (15+ reps), per NSCA guidelines

Knowing your 1RM lets you assign precise working weights and progress them. This is the core reason to estimate 1RM — it turns a training program's percentages into concrete barbell loads for each lift.

Estimated 1RM is most accurate when the test set is heavy (about 2-6 reps) and taken close to failure with good form.

Accuracy degrades at high reps because endurance and technique, not pure strength, increasingly limit the set — a 15-rep set poorly predicts a true single.

The NSCA recommends using sets under roughly 10 reps for reliable estimates. Different formulas agreeing closely is a sign your estimate is trustworthy.

One-rep max is lift-specific: your squat, bench, and deadlift maxes differ, and estimation works best for compound barbell lifts with a clear failure point.

Isolation exercises and machines are less suited to 1RM testing.

Track a separate estimated max for each main lift, since strength ratios between lifts vary by individual and training history. Programming percentages should use the 1RM of the specific lift being trained.

Heavy singles and near-max sets demand a thorough warm-up, proper form, and safety measures:

• spotters for the bench
• safety pins in a rack
• never training to failure alone

The NSCA stresses progressive loading and technique over ego lifting. Beginners should build a base before testing maxes. Estimating 1RM from a moderate set avoids most of the risk of a true max attempt, which is the safer default for most lifters.

Frequent mistakes include:

• estimating from too-high a rep count (inflating error)
• using sloppy form on the test set
• comparing your 1RM to others instead of tracking your own progress
• testing a true max without spotters or warm-up
• applying one lift's percentages to another

Use a heavy set under ~8 reps with good form, compare a couple of formulas, and program each lift from its own estimated max.

Most strength programs re-estimate 1RM every 4-8 weeks, at the end of a training block, rather than weekly — strength changes slowly and frequent max testing adds fatigue and injury risk.

The NSCA recommends periodizing: train through a block using percentages, then estimate a fresh 1RM from a heavy set to update your working loads.

Beginners can progress by simply adding weight each session (linear progression) and retest less formally. Retesting too often produces noise, not signal, and interferes with recovery.