One-Rep Max Formulas Compared: Epley, Brzycki and Lombardi
You do not need to max out to know your max. How the three most used one-rep max formulas work, where they agree and disagree, and how to use the estimate to set your training weights.
A one-rep max (1RM) is the heaviest weight you can lift once with good form. You can estimate it from a harder set of several reps with a formula — Epley, Brzycki and Lombardi are the most widely used — instead of testing it directly. The estimate is close enough to set training weights, and much safer and less tiring than a true max attempt.
The three formulas
| Formula | Equation | Character |
|---|---|---|
| Epley | weight × (1 + reps ÷ 30) | Slightly generous at moderate reps |
| Brzycki (1993) | weight × 36 ÷ (37 − reps) | Conservative at low reps, climbs steeply at high reps |
| Lombardi | weight × reps0.10 | Flattest curve; reads lower at high reps |
Example. A lifter squats 100 kg for 5 reps.
- Epley: 100 × (1 + 5/30) = 116.7 kg
- Brzycki: 100 × 36 ÷ 32 = 112.5 kg
- Lombardi: 100 × 50.10 = 117.5 kg
- Average: about 115.5 kg
The one-rep max calculator runs all three and averages them.
Where they agree and where they don’t
At one rep, every formula returns the weight lifted. Up to about five reps they stay within a few percent of each other. Beyond eight or ten reps they drift apart, because the number of reps you can do with a lighter weight depends more on muscular endurance than on maximal strength, and that varies a lot from person to person and from lift to lift. A 1997 study by LeSuer and colleagues in the Journal of Strength and Conditioning Research found the common equations predicted 1RM well for the bench press and squat but less well for the deadlift, a reminder that the lift matters too.
Practical rule: estimate from a set of 2 to 8 reps, taken close to failure with good form. That is why our calculator stops at 12.
Using the estimate
Training programs are often written as percentages of 1RM. Rough guides:
| % of 1RM | Typical reps | Use |
|---|---|---|
| 90–95% | 2–4 | Heavy strength work |
| 80–85% | 5–8 | Strength and size |
| 65–75% | 9–15 | Muscle growth, technique under load |
| 50–60% | 15+ | Warm-ups, endurance, deload weeks |
These are averages. Some people can do more reps at a given percentage, some fewer, and the numbers differ between exercises. Use the chart to choose a starting weight, then adjust by feel: if the last two reps of a set are smooth, add weight next time.
Strength, calories and your TDEE
Lifting builds and preserves muscle, but it burns fewer calories during the session than most people think: the 2024 Compendium of Physical Activities rates general weight training at 3.5 METs and vigorous powerlifting or bodybuilding at 6. An hour of typical gym work might add 150 to 300 calories above rest for most adults. Its larger role in your energy balance is long term: keeping muscle while you diet. You can add your sessions to the TDEE calculator and use the workout planner to fit strength days into your week.
Frequently asked questions
How do I calculate my one-rep max without testing it?
Do a hard set of 2 to 8 reps with good form, then plug the weight and reps into a formula such as Epley (weight × (1 + reps ÷ 30)). Averaging two or three formulas smooths out their differences.
Which one-rep max formula is most accurate?
No single formula wins for everyone or every lift. They agree closely at low reps and drift apart at higher reps. For most people, an average of Epley, Brzycki and Lombardi from a set of 3 to 6 reps is a sound estimate.
Is it safe to test a true one-rep max?
For experienced lifters with good technique and a spotter, yes, occasionally. For beginners, an estimate from a set of several reps gives most of the information with far less risk.
How often should I re-estimate my max?
Every four to eight weeks, or at the end of a training block, using a fresh hard set.