How is 1RM calculated?
Your 1RM (one-repetition maximum) is the heaviest weight you can lift once with good technique. Testing it directly is tiring and risky outside a meet, so estimation formulas work from a lighter set instead.
This calculator runs seven established formulas (Epley, Brzycki, Lombardi, Mayhew, O'Conner, Wathan and Lander) and uses their average, which is steadier than any single formula. Past 10 reps the formulas drift apart: a set of 3 to 6 reps gives the most reliable estimate.
Programming from your 1RM
Most strength programs are written as percentages of 1RM: around 70 % for volume, 80-90 % for strength, 90 %+ for peaking. The chart above gives each load directly, rounded to loadable plates.
An estimated max is still an estimate: fatigue, sleep and technique move it day to day. That is why coaches track e1RM session after session rather than one number, which CoachForce does automatically from your athletes' training logs.
Frequently asked questions
Which 1RM formula is the most accurate?
None wins everywhere. Epley and Brzycki agree closely up to 10 reps; Lombardi slightly underestimates long sets. The average used here reduces each formula's error.
How many reps should I use to estimate my 1RM?
3 to 6 reps at a high effort (RPE 8-10). Past 10 reps, muscular endurance matters more than maximal strength and the estimate gets less reliable.
Does an estimated 1RM work for every exercise?
The formulas are calibrated on big compound lifts (squat, bench press, deadlift). On isolation exercises they often overestimate the max.
Should I test my true 1RM?
Not necessarily. A regularly tracked e1RM is enough to program. True maxes are best tested at a meet or at the end of a peaking block, when fatigue is low.
How do I find my max squat without testing it?
Do one heavy set of 3 to 5 reps with good form, then enter the weight and reps in the calculator. It estimates your one-rep max within a few percent, without the risk and fatigue of a true test.
How do I calculate my bench press max?
Same method: a set of 3 to 6 reps close to failure, then the formula. On the bench press, estimates from short sets are very reliable because the lift is stable and less technical.
What is the 1RM formula?
The best known is Epley: 1RM = weight × (1 + reps / 30). Brzycki gives 1RM = weight × 36 / (37 − reps). The calculator shows seven formulas and their average.