One Rep Max Calculator

Enter your lifting weight and reps to estimate your 1RM (one-rep max) using the Epley, Brzycki, and Lander formulas. Gauge your strength with this free 1RM calculator.

How to Use

  1. Enter weight

    Input the weight you lifted in kilograms (kg) or pounds (lbs).

  2. Enter reps

    Input the number of repetitions you completed with that weight.

  3. View results

    See your estimated 1RM and recommended weights for various rep ranges.

What is 1RM?

1RM (One Repetition Maximum) is the heaviest weight you can lift exactly once with proper form in a given exercise. In strength lifts like the bench press, squat, and deadlift, it serves as the benchmark for your absolute strength.

1RM matters because every training intensity can be designed as a percentage of it (%1RM). The same 60 kg is a demanding 75% for someone with an 80 kg 1RM, but only a light 50% for someone with a 120 kg 1RM.

  • Strength goal: 85-95% range (2-6 reps)
  • Hypertrophy goal: 70-85% range (6-12 reps)
  • Endurance goal: 50-70% range (12-20 reps)

Because testing a true 1RM directly carries a high injury risk, it is common to estimate it with a formula from a weight you can lift for several reps.

The Formula

This calculator gives you the results of two validated formulas along with their average.

Epley formula: 1RM = weight × (1 + reps / 30)

Brzycki formula: 1RM = weight × 36 / (37 − reps)

For example, if you lifted 100 kg for 5 reps:

  • Epley: 100 × (1 + 5/30) = 100 × 1.167 ≈ 116.7 kg
  • Brzycki: 100 × 36/(37−5) = 100 × 1.125 = 112.5 kg
  • Average estimated 1RM = (116.7 + 112.5) / 2 ≈ 114.6 kg

Here 'weight' is the load you actually lifted (kg) and 'reps' is the number of repetitions completed at that load. Both formulas are most accurate in the 1-10 rep range.

Frequently Asked Questions

What is 1RM?
1RM (One Repetition Maximum) is the maximum weight you can lift for a single repetition with proper form in a given exercise. It is the key benchmark for setting and programming strength-training intensity, and it is usually estimated from a weight you can lift for several reps to avoid the injury risk of a true max attempt.
What is the difference between the Epley and Brzycki formulas?
The Epley formula (1RM = weight × (1 + reps/30)) tends to estimate a higher value as the rep count rises, while the Brzycki formula (1RM = weight × 36/(37−reps)) gives a more conservative result at 10 reps or fewer. This calculator shows both results and their average together.
How do I use the RM percentage table?
Set your training target using the weight that corresponds to a specific percentage of your 1RM. For strength gains, train at 85-95% (2-6 reps); for hypertrophy, 70-85% (6-12 reps); for muscular endurance, 50-70% (12-20 reps). These are estimates based on NSCA guidelines and vary by individual.
Can I just test my 1RM directly?
If a beginner, or anyone without a thorough warm-up, attempts a true 1RM, form tends to break down and injury risk is high. That is why estimating from a weight you can lift for 3-10 reps is safer and more practical. If you do need a direct test, work up gradually from a light load with an experienced spotter.
At how many reps is the estimate most accurate?
The estimation formulas were built around the high-intensity range close to 1RM, so they are most accurate from 1 to 10 reps. As reps climb to 15 or 20, muscular endurance becomes a larger factor and the estimate tends to come out higher than reality. When possible, enter a result measured at around 5 reps.
Why does the estimated 1RM differ from a measured one?
Because the formulas are based on a statistical average, error arises from individual muscle-fiber composition, training experience, neural adaptation, and the specific lift. Even for the same person, the estimate's accuracy can differ between the squat and the bench press. Treat the estimate not as an absolute figure but as a reference point for setting training intensity.
Why use the average of the two formulas?
Epley tends to estimate slightly high and Brzycki slightly low, so relying on a single formula can introduce bias. Averaging the two cancels out the deviation on each side for a more stable estimate, which is why this calculator presents the average estimated 1RM as its default reference.
Do the same formulas apply to women and beginners?
The Epley and Brzycki formulas do not distinguish by sex and apply equally. That said, beginners have less neural adaptation, so at higher reps their true 1RM tends to come out lower than the estimate. It is safer to start conservatively at first and raise the intensity gradually.
Updated 2026 — WHO standards

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