1RM Calculator (One-Rep Max)
Last updated: 2026-06-25
Your 1RM (one-rep max) is the most you can lift for a single rep, estimated from the weight and reps you did. The Epley formula is 1RM = weight x (1 + reps / 30), and the Brzycki formula is 1RM = weight x 36 / (37 - reps).
Example: lifting 100 kg for 5 reps gives an Epley estimate of about 116.7 kg and a Brzycki estimate of about 112.5 kg.
Enter weight and reps
Estimated 1RM (Epley/Brzycki average)
0kg
| Intensity (%1RM) | Goal | Weight |
|---|---|---|
| 95% | Max strength (1-2 reps) | |
| 90% | Strength (2-4 reps) | |
| 85% | Strength & power (5-6 reps) | |
| 80% | Hypertrophy (8 reps) | |
| 75% | Hypertrophy (10 reps) | |
| 70% | Hypertrophy & endurance (12 reps) | |
| 60% | Muscular endurance (15+ reps) |
Estimates are for reference only. Error grows when reps go well above 10, and any true max-weight attempt should be done safely with a spotter.
How to use
- Enter weight — Enter the weight (barbell load) you lifted in one set, in kg.
- Enter reps — Enter how many reps you completed with good form without failing (1-10 recommended).
- View results — Press Calculate to see your estimated 1RM from the Epley and Brzycki formulas plus the weight at each %1RM intensity.
The 1RM formulas and how to use %1RM
Your 1RM (One-Rep Max) is the maximum weight you can lift for a single rep with proper form. Because testing a true max is risky, it is usually estimated from a set of several reps at a moderate weight. The two most widely used formulas are below.
| Formula | Equation | Notes |
|---|---|---|
| Epley | weight x (1 + reps / 30) | Estimates 1RM slightly higher at higher reps |
| Brzycki | weight x 36 / (37 - reps) | Stable at 10 reps or fewer; diverges to infinity at 37 reps |
Both formulas return the lifted weight when reps = 1, and the estimated 1RM rises as reps increase. They are most accurate in the 1-10 rep range, and this calculator presents the average of the two as the headline value.
Your estimated 1RM is the basis for setting training intensity. For example, train maximal strength at 85-95% for low reps, hypertrophy at 67-80% for moderate reps, and muscular endurance at 60% or below for high reps. See the How to Calculate and Use Your 1RM guide for more detail.
Frequently asked questions (FAQ)
What is a 1RM (one-rep max)?
Your 1RM (One-Rep Max) is the maximum weight you can lift for a single rep with proper form. It is a benchmark of strength and the reference value used to set training intensity (%1RM).
How is a 1RM estimated?
This calculator estimates your 1RM from the weight and reps using the Epley formula (1RM = weight x (1 + reps/30)) and the Brzycki formula (1RM = weight x 36 / (37 - reps)). It also shows the average of the two.
Up to how many reps stays accurate?
The formulas are generally most accurate in the 1-10 rep range. As reps climb (especially above 12), muscular endurance becomes a bigger factor and 1RM error grows, so heavier sets with fewer reps give the most accurate estimate.
How do I use %1RM?
For maximal strength train at 85-95% for low reps (2-5), for hypertrophy at 67-80% for moderate reps (8-12), and for muscular endurance at 60-67% or below for high reps. Multiply your estimated 1RM by the target percentage to set the day's working weight.
Is it okay to actually test my true 1RM?
For beginners or when training alone without a spotter, testing a true 1RM carries a high injury risk. For safety it is better to use an estimate from a moderate rep set. The values here are estimates for reference only.
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Last updated: 2026-06-25