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One Rep Max Calculator (1RM)
Estimate your one-rep max from a sub-max set. Compares Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner, and Wathan formulas.
HEALTHEstimate your one-rep max (1RM) for bench press, squat, deadlift, or any compound lift from a sub-max set. Compares seven validated formulas (Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner, Wathan) and outputs a training-percentage table.
Each formula reaches 1RM from weight × reps differently. Epley: 1RM = w × (1 + r/30). Brzycki: 1RM = w × 36/(37-r). They converge for 1-5 reps and diverge above 10. Use a true near-failure set (1 rep in reserve) for accuracy. The percentage table maps 1RM percentages to typical rep ranges: 90%+ for singles, 80% for 6-8 reps, 70% for 10-12 reps, 60% for 15+.
Disclaimer: Estimates only. Actual 1RM varies with form, fatigue, technique. Always test under a spotter for true 1RM attempts.
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Frequently Asked Questions
How accurate is the 1RM calculator?
For 1-5 rep sets taken to true near-failure, 1RM formulas are accurate within about 5%. Above 10 reps they get unreliable because muscular endurance and 1RM strength involve different physiology. The seven formulas (Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner, Wathan) typically agree within 5-15 lbs at submaximal reps - the average is more reliable than any single formula.
Should I actually test my 1RM?
For most lifters: no. Testing 1RM is taxing, injury-prone, and the result drifts with daily fatigue, sleep, and recent training. Estimating from a 3-5 rep max gives you the same training prescription with much lower risk. Powerlifters do test in meets, but they peak for weeks beforehand and have judges, spotters, and equipment standards.
How do I program with 1RM percentages?
Strength work: 80-95% for 1-5 reps, 3-6 sets. Hypertrophy: 65-80% for 6-12 reps, 3-5 sets. Endurance: 50-65% for 12-20 reps, 2-4 sets. Most evidence-based programs cycle through these zones (linear or undulating periodization). For most natural lifters, 70-85% range produces the best size-and-strength returns.
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