One-Rep Max Calculator
Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition with correct form. Knowing it allows you to programme training loads precisely using percentages: for example, 80 percent of 1RM for hypertrophy work, or 90 percent for strength peaking. This calculator uses three independently published formulas (Epley, Brzycki, and Lander) to estimate your 1RM from a submaximal set of 1 to 10 repetitions. Enter the weight you lifted and the number of reps completed, and the calculator returns the 1RM estimate from each formula, the average of all three, and a complete percentage breakdown table from 50 to 100 percent. Valid for 1 to 10 reps; accuracy decreases above 10 reps as muscular endurance becomes a larger factor. Supports both kilograms and pounds.
Estimated 1RM (average): --
Percentage training table
Based on average estimated 1RM. Update inputs above to recalculate.
| % of 1RM | Weight | Typical rep range | Training purpose |
|---|---|---|---|
| 100% | -- | 1 | Maximal strength test |
| 95% | -- | 1 to 2 | Peaking / competition |
| 90% | -- | 2 to 3 | Maximal strength |
| 85% | -- | 3 to 4 | Strength |
| 80% | -- | 4 to 6 | Strength / power |
| 75% | -- | 6 to 8 | Strength / hypertrophy |
| 70% | -- | 8 to 10 | Hypertrophy |
| 65% | -- | 10 to 12 | Hypertrophy / endurance |
| 60% | -- | 12 to 15 | Muscular endurance |
| 55% | -- | 15 to 20 | Endurance / warm-up |
| 50% | -- | 20+ | Warm-up / technique |
The three 1RM formulas
Epley (1985):
1RM = weight x (1 + reps / 30)
Brzycki (1993):
1RM = weight x 36 / (37 - reps)
Lander (1985):
1RM = 100 x weight / (101.3 - 2.67123 x reps)
Worked example
Weight = 100 kg, Reps = 5:
- Epley: 100 x (1 + 5/30) = 100 x 1.1667 = 116.67 kg
- Brzycki: 100 x 36 / (37 - 5) = 3,600 / 32 = 112.50 kg
- Lander: 100 x 100 / (101.3 - 13.356) = 10,000 / 87.944 = 113.71 kg
- Average: (116.67 + 112.50 + 113.71) / 3 = 114.29 kg
Safety and training considerations
Estimating 1RM from a submaximal set is safer than a direct 1RM test, particularly for beginners. Keep the following in mind:
- Use 5 to 8 reps for the most reliable estimates (the formulas converge near this range).
- Stop the set before form breaks down. A failed rep or poor technique invalidates the estimate.
- Always warm up progressively: two to three warm-up sets before your working set.
- Have a spotter for barbell exercises such as bench press and back squat.
- Re-test every four to eight weeks, not every session. Frequent retesting accumulates fatigue.
One-rep max calculator: frequently asked questions
What is a one-rep max (1RM)?
A one-rep max (1RM) is the maximum weight you can lift for a single repetition of a given exercise with correct form. It is the standard measure of absolute strength in resistance training and powerlifting. Knowing your 1RM lets you calculate training loads as percentages, which is the foundation of periodised strength programs.
Which 1RM formula is most accurate?
No single formula is universally most accurate; accuracy depends on the individual and the number of reps used. The Epley formula (weight x (1 + reps/30)) tends to overestimate slightly at lower rep ranges. The Brzycki formula (weight x 36 / (37 - reps)) is widely used and performs well for 1 to 6 reps. The Lander formula (100 x weight / (101.3 - 2.67123 x reps)) is often considered the most accurate for 7 to 10 reps. Using the average of all three reduces individual formula bias.
Is it safe to test my 1RM directly?
Directly testing a 1RM carries injury risk, especially for beginners or those without a spotter. This calculator lets you estimate 1RM from a submaximal effort (for example, a weight you can lift 5 times) and is valid for 1 to 10 reps. Keep reps at 10 or below for best accuracy. Always use a spotter, proper technique, and adequate warm-up. Beginners should wait until they have 6 to 12 months of consistent training before testing or estimating 1RM.
How do I use 1RM percentages in training?
Percentage-based training prescribes load relative to your estimated 1RM. Common zones: 50 to 60 percent for warm-up and technique work; 60 to 70 percent for muscular endurance (12 to 20 reps); 70 to 80 percent for hypertrophy (8 to 12 reps); 80 to 90 percent for strength (3 to 6 reps); 90 to 100 percent for maximal strength and peaking (1 to 3 reps). Programs like 5/3/1 and NSCA guidelines use these percentages as their primary load prescription tool.
Why are the formulas only valid for 1 to 10 reps?
All three formulas were derived from data collected on submaximal lifting sets. As rep count increases beyond 10, the relationship between weight and 1RM becomes less linear because muscular endurance and aerobic capacity start contributing more than pure strength. Predictions from sets of more than 10 reps tend to significantly overestimate true 1RM. The National Strength and Conditioning Association recommends using 10 or fewer reps for 1RM estimation.
Official sources
- Brzycki, M. (1993). Strength testing: predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation and Dance, 64(1), 88-90.
- Epley, B. (1985). Poundage chart. Boyd Epley Workout. University of Nebraska.
- Lander, J. (1985). Maximums based on reps. National Strength and Conditioning Association Journal, 6(6), 60-61.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology. General information only.