Which one rep max formula is the main result?

The calculator displays the Epley estimate as the primary result. It also reports Brzycki and Lombardi estimates underneath. All three use the weight and repetitions you entered, keep the selected unit, and round to two decimal places. Differences between formulas are normal.

What rep range works best for estimating 1RM?

the calculator accepts 1 to 20 repetitions, and the code rejects values at or above 37 because the Brzycki denominator would break down. In practice, estimated max formulas are usually more meaningful when the set is a clean, hard lower-rep effort, often somewhere around 2 to 10 reps.

Can I use pounds or kilograms?

Yes. Choose pounds or kilograms before entering the lifted weight. The calculator does not convert between units; it simply keeps the result in the unit you selected. If you enter 100 kg, the output is in kilograms. If you enter 225 lb, the output is in pounds.

Is an estimated 1RM safe to attempt?

Not automatically. A formula estimate is not a guarantee that you can safely lift that load today. Technique, fatigue, warm-up, equipment, spotting, pain, and exercise choice matter. Use conservative loading, proper setup, and qualified coaching or medical guidance when appropriate.

Why do the formulas disagree?

Each formula makes a different assumption about how repetitions relate to maximal strength. Epley grows linearly with reps, Brzycki rises faster as reps approach its upper limit, and Lombardi uses a power curve. Exercise type, range of motion, and muscular endurance can make one estimate fit better than another.

How should I use the result in training?

Use it as a planning estimate for training percentages, not as a required test. Many lifters use estimated 1RM to select working weights, compare similar rep sets over time, or avoid frequent maximal attempts. Recalculate with consistent technique and similar exercises for the cleanest trend.

One Rep Max Calculator

$\text{Epley 1RM} = \text{weight} \times (1 + 0.0333 \times \text{reps})$

The Brzycki result is:

$\text{Brzycki 1RM} = \text{weight} \times \frac{36}{37 - \text{reps}}$

The Lombardi result is:

$\text{Lombardi 1RM} = \text{weight} \times \text{reps}^{0.1}$

Each result is rounded to two decimal places. Epley adds a fixed percentage for each repetition. Brzycki uses a fraction that rises as repetitions increase. Lombardi uses a power function, which often sits near Epley for common lower-rep examples but can diverge depending on reps.

Worked example

Suppose you lift 135 lb for 5 repetitions. The Epley estimate is:

$135 \times (1 + 0.0333 \times 5) = 157.4775$

Rounded like the calculator, that displays as 157.48 lb. Brzycki is:

$135 \times \frac{36}{37 - 5} = 151.875$

That displays as 151.88 lb. Lombardi is:

$135 \times 5^{0.1} = 158.5709$

That displays as 158.57 lb. The copy text would summarize the same three estimates in the selected unit. If you enter kilograms instead, the arithmetic is identical and the labels change to kg.

Interpreting an estimated max

A calculated 1RM is most useful as a consistent yardstick. If your Epley squat estimate rises from 140 kg to 150 kg using the same depth and similar rep range, that likely reflects progress even if you never test a true single. Strength coaches often prescribe work sets as percentages of a max or estimated max, but the estimate should be adjusted for the day. Poor sleep, illness, a hard previous session, or a new exercise variation can make a normal percentage feel unusually heavy.

ACSM physical-activity guidance supports resistance training as part of adult fitness, but it does not mean maximal attempts are necessary for everyone. Many people can build strength with submaximal sets, progressive overload, and good technique. If your goal is body composition rather than max strength, compare this estimate with the body fat calculator or calorie calculator to keep strength progress in context.

For programming, use the estimate conservatively. A set of five done after several warm-up sets may predict differently than a fresh set of five. A paused bench press, touch-and-go bench press, dumbbell press, and machine press should each have their own history. The cleaner your input set is, the more useful the trend becomes.

Choosing inputs

Use a recent set from the same lift you want to estimate. If the set was stopped with many reps in reserve, the calculator will underestimate your current max because the rep count does not represent a hard effort. If the set used bouncing, altered depth, straps on one attempt but not another, or an unusually long rest, write that context down. Consistency makes the estimate more useful than chasing the largest possible number.

Common mistakes

Entering a set with sloppy calculator, shortened range of motion, or help from a spotter.
Using a high-rep endurance set and treating the estimate as equally reliable as a lower-rep strength set.
Mixing exercises. A leg press 1RM estimate is not a squat 1RM estimate.
Assuming the highest formula is the correct one because it is more exciting.
Attempting the predicted number without a progressive warm-up, safeties, or spotting.

Limitations and health disclaimer

This calculator provides general educational fitness information only. It is not medical advice, coaching supervision, or a clearance to attempt maximal lifting. Stop if you have pain, use appropriate equipment, and seek qualified professional guidance if you are new to heavy resistance training, returning from injury, or managing a health condition.

Sources

ACSM, Physical Activity Guidelines — resistance-training context within adult activity guidance.
CDC, Adult physical activity basics — public-health guidance including muscle-strengthening activity.
WHO, Physical activity — global recommendations for activity and health.