One Rep Max Calculator - 1RM with Epley and Brzycki

The two formulas

A one-rep max (1RM) is the heaviest weight you can lift once with good form. Testing it directly is tiring and carries more risk, so most lifters estimate it from a heavier set taken close to failure. Two formulas dominate.

Epley (1985): 1RM = weight × (1 + reps ÷ 30). It came from a poundage chart in Boyd Epley's strength training manual at the University of Nebraska. Brzycki (1993): 1RM = weight × 36 ÷ (37 − reps), published by Matt Brzycki in the Journal of Physical Education, Recreation & Dance. Neither was a large lab study; both were practical coaching tools that later research found reasonably accurate for sets of up to about 10 reps.

The two agree exactly at 10 reps. Below 10, Epley gives slightly higher numbers; above 10, Brzycki climbs faster and becomes unreliable. The calculator shows both and uses their average for the training table, which dampens the bias of either one.

Worked example

You bench 225 lb for 5 reps. Epley: 225 × (1 + 5/30) = 225 × 1.1667 = 262.5 lb. Brzycki: 225 × 36 ÷ 32 = 253.1 lb. Average: 257.8 lb.

Your 85% working weight is 257.8 × 0.85 = 219 lb, rounded to 220 for plates. By Epley's math, 85% of max is good for about 5 reps, which lines up with what you just did: a good sign the estimate is realistic.

In metric: 100 kg for 8 reps gives Epley 126.7 kg, Brzycki 124.1 kg, average about 125 kg.

Using the percentage table

Most programs prescribe loads as a percentage of 1RM. Roughly: 85-100% for heavy strength work in sets of 1-5, 70-85% for hypertrophy in sets of 6-12, and below 70% for speed work, technique, or high-rep endurance. The "approx. reps" column inverts the Epley formula (reps = 30 × (1 ÷ percentage − 1)) to show how many reps each load should allow when taken near failure.

The plate column rounds to the nearest 5 lb or 2.5 kg so you can load a standard barbell without doing math between sets.

Common mistakes

Using a high-rep set. Beyond 10 reps, fatigue and conditioning dominate and every formula drifts. A hard set of 3-6 reps gives the best estimate.

Using a set that was not close to failure. If you had 3 reps left in the tank, the formula underestimates your max. Either push the set to about 1 rep in reserve or add your reps in reserve to the count.

Applying bench numbers to deadlifts. Formulas were built mostly on bench press and squat data. Lower-body and highly technical lifts can differ, and individual muscle fiber makeup changes how many reps you can do at a given percentage.

Testing a true max without safety. If you do test, use a spotter or safety arms, warm up progressively, and stop the session if form breaks down.

Recalculating every session. Estimated 1RMs bounce with sleep, food, and stress. Re-estimate every 4-8 weeks or at the end of a training block.

Tracking progress without maxing out

You do not need to test a true single to know you are getting stronger. Pick one benchmark set, for example your heaviest set of 5 on squat, and run it through the calculator every few weeks. If 245 × 5 becomes 255 × 5, your estimated max rose about 12 lb even though you never attempted it. Keeping the same rep range each time matters more than which formula you use, because each formula's bias stays constant and cancels out when you compare your own numbers over time.

Who should skip max testing

Heavy singles spike blood pressure, especially if you hold your breath. If you have uncontrolled high blood pressure, heart disease, a recent hernia, eye pressure problems like glaucoma, or are pregnant, talk to a clinician before lifting near-maximal loads. Estimating from a moderate set of 5-10 reps is a safer way to set training weights. Stop immediately and seek care for chest pain, sudden severe headache, or numbness.