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One Rep Max Calculator

Estimate the most you could lift for one rep from a lighter set you have already done — no risky max attempts needed.

Quick answer

Epley: 1RM = weight × (1 + reps ÷ 30). Lifting 100 kg for 5 reps puts your one-rep max at about 115 kg. Most accurate from sets of 3–6 hard reps. Support training with enough protein — see the protein calculator.

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  • Fitness
  • Updated October 2026
lb

Most accurate for 2–10 reps.

Estimated one-rep max

212 lb

Average of Epley and Brzycki

Epley
215.8 lb
Brzycki
208.1 lb
95% of 1RM
201 lb
90% of 1RM
191 lb
85% of 1RM
180 lb
80% of 1RM
170 lb
75% of 1RM
159 lb
70% of 1RM
148 lb
65% of 1RM
138 lb
60% of 1RM
127 lb
Show the working
  1. Epley = 185 × (1 + 5 ÷ 30) = 215.8
  2. Brzycki = 185 × 36 ÷ (37 − 5) = 208.1

About the One Rep Max calculator

Testing a true one-rep max is tiring and carries injury risk. Rep-max formulas estimate it from a hard set of several reps, and most strength programs prescribe working weights as a percentage of that 1RM.

Estimates are most reliable from sets of 2–10 reps taken close to failure with good form. The calculator averages the Epley and Brzycki formulas, which agree closely in that range.

How to use it

  1. Enter the weight you lifted and choose lb or kg.
  2. Enter how many clean reps you completed.
  3. Read your estimated 1RM and the training weights at 60–95%.

The formula

Epley: 1RM = w × (1 + reps ÷ 30) · Brzycki: 1RM = w × 36 ÷ (37 − reps)

  • The result shown is the average of both.
  • With 1 rep, the weight lifted is the 1RM.

Worked example

100 kg for 5 reps

  1. Epley: 100 × (1 + 5/30) = 116.7 kg.
  2. Brzycki: 100 × 36 ÷ 32 = 112.5 kg.
  3. Average ≈ 115 kg.

Frequently asked questions

How many reps give the best estimate?

Sets of about 3–6 reps to near-failure tend to give the most accurate estimates. Above 10–12 reps, endurance starts to skew the result.

Does it work for every exercise?

It works best for big barbell lifts like squat, bench press and deadlift. It is less reliable for small isolation exercises and machines.

What percentage of 1RM should I train at?

Roughly 80–90% for strength (3–6 reps), 65–80% for muscle growth (6–12 reps) and below 65% for technique and endurance work.

Results are estimates for healthy adults, not medical advice. Talk to a doctor or registered dietitian before major changes to diet or training, especially if you are pregnant or have a health condition.

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