Estimate your one-rep max (1RM) from any weight and rep count, plus training percentages for every goal.
Calculate 1RM ↓Works best for sets of 1–10 reps performed close to failure.
Training percentages:
This range builds raw strength and neuromuscular efficiency — the ability to recruit more muscle fibres for a given movement. It's demanding on the nervous system, so it's typically programmed for lower total weekly volume with longer rest periods (3–5 minutes) between sets.
This range is generally considered the sweet spot for muscle growth, balancing enough mechanical tension per rep with enough total volume to drive adaptation. Rest periods of 60–90 seconds are common, allowing for higher training density without fully compromising the next set's quality.
Lighter loads for higher reps build muscular endurance and can still contribute to hypertrophy when taken close to failure, though typically with more metabolic fatigue (the 'burn') than heavier work. This range is also commonly used for technique practice, warm-up sets, and rehabilitation contexts where heavier loading isn't appropriate.
This calculator averages two widely used prediction formulas: the Epley formula (1RM = weight × (1 + reps/30)), developed by Boyd Epley for strength coaching in the 1980s, and the Brzycki formula (1RM = weight × 36 / (37 − reps)), developed by Matt Brzycki around the same era. Both formulas were built by fitting equations to real lifting data, and they tend to produce slightly different estimates — Epley generally runs a bit higher at higher rep counts, Brzycki a bit lower — so averaging them gives a reasonably balanced middle estimate.
These formulas are most accurate for sets of 1–10 reps performed close to muscular failure with good technique — above 12 reps, prediction accuracy drops noticeably since the relationship between reps and load becomes less linear at very high rep counts. They also don't account for individual differences in muscle fibre type, training experience, or which exercise is being tested — 1RM prediction tends to be more accurate for compound barbell lifts (squat, bench, deadlift) than for machines or isolation exercises. Treat the result as a solid planning estimate, not a guaranteed number you'd hit on an actual single-rep attempt.
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