One-Rep Max Calculator
Estimate the most you could lift for a single rep from a set you have already done. Enter the weight and how many reps you completed to get your 1RM and a full training percentage table.
Enter a weight and reps to estimate your one-rep max.
- Enter the weight you lifted. The load on the bar for the set you are basing the estimate on, in kilograms or pounds.
- Enter the reps you completed. How many clean reps you did with that weight. Estimates are most accurate at 10 reps or fewer.
- Read your estimated 1RM. The calculator averages several established rep-max formulas, then shows a full percentage table for programming your training loads.
You do not need to attempt a true maximal lift to know roughly what it would be. The number of reps you can complete with a given weight has a predictable relationship to your single-rep maximum, and several researchers have fit equations to that relationship over the years.
This calculator runs your weight and reps through four of the most established formulas — Epley, Brzycki, Lombardi, and Lander — and averages them. Because each formula is biased slightly differently, the average is steadier than trusting any one of them alone. You can expand the per-formula estimates in the results to see the spread.
Most structured strength programs express working weights as a percentage of your one-rep max. Heavy strength work typically lives at 85–95% for low reps, hypertrophy (muscle-building) work around 67–80% for moderate reps, and lighter technique or endurance work below that.
The percentage table turns your estimate into concrete loads for each of these zones, so you can pick the weight that matches the set and rep scheme your program prescribes. Round to whatever your available plates allow.
- Use a lower rep set. Estimates from sets of 2–5 reps are the most accurate. The higher the reps, the more individual endurance skews the result.
- Only count clean reps. Include reps done with good form through a full range of motion — not grinding, half-range, or assisted reps.
- Base it on a near-limit set. The relationship assumes the set was genuinely challenging. A weight you stopped well short of failure with will underestimate your max.
- Estimate each lift separately. Your 1RM differs by exercise, so use a set performed on the specific lift you care about.
One-rep-max estimates (average of established formulas)
Epley: 1RM = w x (1 + r/30)
Brzycki: 1RM = w x 36 / (37 - r)
Lombardi: 1RM = w x r^0.10
Lander: 1RM = 100 x w / (101.3 - 2.67123 x r)- w
- = weight lifted
- r
- = number of repetitions completed
- 1RM
- = estimated one-repetition maximum
This calculator averages these four formulas because each is slightly biased at different rep ranges; the average is more stable than any single equation. All rep-max formulas are estimates and lose accuracy above about 10 reps.
What is a one-rep max (1RM)?
Your one-rep max is the heaviest weight you can lift for a single repetition of an exercise with good form. It is the standard reference point for strength: training programs often prescribe loads as a percentage of your 1RM rather than as fixed weights.
How is 1RM estimated without actually testing it?
Rep-max formulas use the fact that the number of reps you can do with a submaximal weight predicts your maximum. If you can lift a weight for several clean reps, formulas like Epley and Brzycki extrapolate the single-rep load. This calculator averages four established formulas for a more stable estimate.
Why does this calculator average several formulas?
Each rep-max equation was fit to different data and is biased slightly differently across rep ranges — Epley tends to read a little higher, Brzycki a little lower, at higher reps. Averaging Epley, Brzycki, Lombardi, and Lander smooths out the quirks of any single formula and gives a more representative number.
How accurate is an estimated 1RM?
Estimates are most accurate when based on sets of about 2–5 reps, and they stay reasonable up to roughly 10 reps. Beyond that, factors like muscular endurance and fatigue tolerance vary so much between people that the prediction becomes unreliable. For the best estimate, use a weight you can lift for 5 reps or fewer.
Is it safe to test my actual one-rep max?
True 1RM testing carries a higher injury risk because it involves a maximal load, often near the point of form breakdown. It should only be attempted by experienced lifters, fully warmed up, with a spotter or safety bars. Estimating your 1RM from a submaximal set is safer and accurate enough for programming for most people.
How do I use the percentage table?
The table converts your estimated 1RM into training loads. If a program calls for 3 sets of 5 at 80% of your 1RM, read the 80% row for the weight to load. The rep counts next to each percentage are typical ranges most lifters can hit at that load — useful for sanity-checking whether a prescribed weight looks right.
Does 1RM differ between exercises?
Yes. Your one-rep max is specific to each lift, so your squat, bench press, and deadlift 1RMs will all be different, and the rep-max relationship varies a little by exercise too. Estimate each lift separately using a set performed on that exact exercise.
References
- Epley B. Poundage Chart. Boyd Epley Workout. Lincoln, NE: Body Enterprises; 1985 (Epley formula).
- Brzycki M. Strength testing: predicting a one-rep max from reps to fatigue. JOPERD. 1993;64(1):88-90.
FitCalcs calculators provide general estimates for healthy adults and are not medical advice.
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