How to calculate 1RM: Lombardi, Brzycki and Epley formulas

By PounceFit Team · Updated on 2026-10-06

Technical content for health and fitness professionals. It reproduces formulas and protocols published in the scientific literature, with the sources at the end of the page. It is not a recommendation and does not replace the judgment of the professional who runs the assessment.

To calculate 1RM (one-repetition maximum) without testing a maximal load, use a set taken to failure with a submaximal load: you record the load and the number of reps and apply an equation that converts that pair into a maximal load. The most common are Lombardi (1989), Brzycki (1993) and Epley (1985). All of them work best with few reps, up to 10, and the error grows as the set gets longer (Reynolds, Gordon and Robergs, 2006).

PounceFit, body assessment software for personal trainers, uses a coefficient table attributed to Lombardi, valid from 1 to 10 reps.

The formulas in full

In all three, L is the load lifted (in kg) and R is the number of complete reps to failure.

Lombardi (1989):

1RM = L × R^0.10

Brzycki (1993):

1RM = L × 36 ÷ (37 - R)

Epley (1985):

1RM = L × (1 + R ÷ 30)

Lombardi is exponential (nonlinear). Brzycki and Epley are linear in practice: the estimated load rises by an almost constant proportion with each extra rep. Reynolds, Gordon and Robergs (2006) note that Lombardi presented the equation in a textbook without showing the underlying data.

What PounceFit calculates

PounceFit does not use the exponential form. It multiplies the load by a coefficient that depends on the number of reps, from a table inherited from the assessment method the app was built on, where it is labeled as Lombardi (1989). We could not verify these values in Lombardi's book, and they do not match the exponential form R^0.10. Treat the PounceFit column as the app's calculation rule, not as a reproduction of the published equation.

The Lombardi, Brzycki and Epley columns are the formulas above, calculated and rounded to two decimals. Note that at 1 rep, the Epley equation returns 3% more than the load lifted, which makes no sense: with 1 rep, the load already is the 1RM.

PounceFit does not calculate above 10 reps. The reason is the finding of Reynolds, Gordon and Robergs (2006): the relationship between load and reps stops being linear and the error grows.

Worked example

A client bench pressed 80 kg (176 lb) and completed 8 reps to failure.

1. PounceFit (table): 80 × 1.27 = 101.6 kg.
2. Lombardi (exponential): 8^0.10 = 1.2311. 80 × 1.2311 = 98.5 kg.
3. Brzycki: 36 ÷ (37 - 8) = 36 ÷ 29 = 1.2414. 80 × 1.2414 = 99.3 kg.
4. Epley: 1 + 8 ÷ 30 = 1.2667. 80 × 1.2667 = 101.3 kg.

The four estimates range from 98.5 to 101.6 kg, a 3 kg spread from the choice of equation alone. Had the same client done 4 reps with a heavier load, the equations would sit closer together (see the table). That is why a set of 3 to 6 reps usually gives a more stable estimate than a set of 10.

From the 1RM, PounceFit calculates relative strength (1RM ÷ body mass) and classifies it by sex and age group. A client weighing 80 kg with an estimated 1RM of 101.6 kg has a relative strength of 1.27.

How to run the test

• Warm-up. Do one or two light sets of the same exercise before the test set (ACSM, 2021).
• Load. Pick a load that leads to failure between 3 and 10 reps. If the client goes past 10, rest and repeat with more weight.
• Technical failure. Count only reps with full range of motion and sound technique. The rep where the client stalls or compensates does not count.
• Same equipment. A 45-degree leg press, a horizontal leg press and a plate-loaded machine give different loads. Record which one you used.
• Rest. Do not test after a hard session for the same muscle group. Fatigue cuts the rep count and lowers the estimate.

Limits of the estimate

• Population. The equations come from specific groups, usually young college students. LeSuer et al. (1997) tested seven equations in 67 college students with no resistance training experience. Correlation with measured 1RM was high (r > 0.95), but all of them underestimated the deadlift.
• Exercise. The error changes from one exercise to another. In the study by Reynolds, Gordon and Robergs (2006), with 70 adults aged 18 to 69, the standard error of the authors' own equation was about 3 kg for the bench press and 16 kg for the leg press, from the 5RM.
• Number of reps. More reps, more error. Every equation was less accurate with a 10RM than with a 5RM (Reynolds, Gordon and Robergs, 2006).
• Training background. On the leg press, distance runners did more than twice as many reps as weightlifters at 70% of 1RM (39.9 vs 17.9) (Richens and Cleather, 2014). The same equation can overestimate for one profile and underestimate for the other.
• Follow-up. To compare assessments, repeat the same exercise on the same equipment with a similar rep range. A change of 2 or 3 kg can fall within the error of the estimate.

A direct 1RM test remains the reference when the client has experience and technique allows it (ACSM, 2021). Estimating from reps works well for beginners, older adults and anyone who should not perform a maximal effort.

For the aerobic part of the assessment, see the VO₂max field tests and max heart rate and heart rate reserve.