One Rep Max Calculator
Estimate your one rep max (1RM) from the weight and reps you lifted, using the Epley, Brzycki and Lombardi formulas. Plus training loads at each % of 1RM.
🏋️ One Rep Max (1RM)
Estimated 1RM
Training Percentages
💡 How the One Rep Max Calculator Works
Your one rep max (1RM) is the heaviest weight you can lift once with good technique. Instead of testing it directly, this calculator estimates it from a set you took close to failure, using three published formulas, and then works out training loads from the average of the three. Lifting 100 kg for 5 reps gives an estimated 1RM of 116.7 kg (Epley), 112.5 kg (Brzycki) and 117.5 kg (Lombardi), an average of 115.5 kg.
The three 1RM formulas
Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Lombardi: 1RM = weight × reps0.1
Training loads = average of the three estimates × percentage.
Worked example: 100 kg for 5 reps
- Epley: 100 × (1 + 5 ÷ 30) = 100 × 1.1667 = 116.7 kg.
- Brzycki: 100 × 36 ÷ 32 = 112.5 kg.
- Lombardi: 100 × 50.1 = 100 × 1.1746 = 117.5 kg.
- Average: (116.7 + 112.5 + 117.5) ÷ 3 = 115.5 kg.
How the formulas compare as reps increase
Estimated 1RM for a 100 kg lift at different rep counts (kg):
| Reps | Epley | Brzycki | Lombardi | Average |
|---|---|---|---|---|
| 1 | 103.3 | 100.0 | 100.0 | 101.1 |
| 2 | 106.7 | 102.9 | 107.2 | 105.6 |
| 3 | 110.0 | 105.9 | 111.6 | 109.2 |
| 5 | 116.7 | 112.5 | 117.5 | 115.5 |
| 8 | 126.7 | 124.1 | 123.1 | 124.6 |
| 10 | 133.3 | 133.3 | 125.9 | 130.9 |
| 12 | 140.0 | 144.0 | 128.2 | 137.4 |
| 15 | 150.0 | 163.6 | 131.1 | 148.2 |
The formulas agree closely at low reps and drift apart as reps rise. At 15 reps Brzycki gives 163.6 kg but Lombardi only 131.1 kg. At 1 rep, Brzycki and Lombardi return the weight itself, while Epley adds about 3%, so if you enter a true single the Brzycki and Lombardi figures are the right ones.
How accurate are 1RM estimates?
Estimates are most reliable from sets of 10 reps or fewer. A 2008 study in the Journal of Strength and Conditioning Research tested 14 equations on 103 college women's bench press before and after 12 weeks of training and found predictions improved when fewer than 10 reps to fatigue were used. With sets of up to 10 reps, Brzycki and Lombardi came within about 1.5 kg of the measured average, while over a wider range of reps Brzycki overestimated noticeably.
- Go close to failure. The formulas assume your set was a true maximum for that many reps; stopping with reps in reserve underestimates your 1RM.
- Use 3–10 reps with consistent technique for the best estimate.
- Exercises differ. The same formula can fit one lift better than another, and individuals vary, so treat the result as a guide.
NSCA percentage chart
The National Strength and Conditioning Association publishes this relationship between the number of reps you can complete and the percentage of your 1RM. You can read it both ways: to estimate 1RM from a set, or to choose a load for a target number of reps.
| Maximum reps | % of 1RM |
|---|---|
| 1 | 100% |
| 2 | 95% |
| 3 | 93% |
| 4 | 90% |
| 5 | 87% |
| 6 | 85% |
| 7 | 83% |
| 8 | 80% |
| 9 | 77% |
| 10 | 75% |
| 12 | 70% |
For example, the NSCA notes that 8 reps at 160 lb suggests a 1RM of about 200 lb, since 8 reps corresponds to 80%.
Training loads from your 1RM
Loads for an estimated 1RM of 115.5 kg (100 kg × 5):
| % of 1RM | Load (kg) |
|---|---|
| 95% | 109.8 |
| 90% | 104.0 |
| 85% | 98.2 |
| 80% | 92.4 |
| 75% | 86.7 |
| 70% | 80.9 |
| 65% | 75.1 |
| 60% | 69.3 |
The NSCA's general guidelines, as summarised by the U.S. Department of Defense's Human Performance Resource Center, are:
| Goal | Load | Reps |
|---|---|---|
| Strength | At least 85% of 1RM | 4–6 |
| Muscle size (hypertrophy) | 67–85% of 1RM | 6–12 |
| Muscular endurance | Less than 67% of 1RM | 12 or more |
The calculator shows 90%, 80% and 70% as quick reference points. By the NSCA ranges, 90% is strength work, while 80% and 70% both fall in the hypertrophy range.
Estimating vs testing a true 1RM
A true 1RM test needs a thorough warm-up, good technique and, for lifts like the bench press and squat, a spotter or safety bars. If you train alone, an estimate from a multiple-rep set is the safer option. For technical lifts such as the back squat or power clean, the HPRC suggests keeping multiple-rep tests to about 5 reps or fewer, because form breaks down as fatigue builds. If a max attempt fails, rest 2–4 minutes before trying a lighter load.
Using your 1RM
- Re-estimate every few weeks as you get stronger, so your training loads keep pace.
- Use a separate estimate for each lift; your bench press 1RM tells you nothing about your squat.
- Compare your lifts with typical standards using the lifting strength calculator.
This calculator is for healthy adults. If you're new to strength training, returning from injury or have a medical condition, get guidance from a qualified coach or health professional before attempting heavy lifts.
Sources
- National Strength and Conditioning Association (NSCA): Training load chart
- Human Performance Resource Center (U.S. Department of Defense): One rep max for strength
- Mayhew JL, et al. (2008). Accuracy of prediction equations for determining one repetition maximum bench press in women before and after resistance training. Journal of Strength and Conditioning Research, 22(5), 1570–1577
- Epley B (1985). Poundage chart. Boyd Epley Workout. Lincoln, NE.
- 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.
- Lombardi VP (1989). Beginning Weight Training. Dubuque, IA: W.C. Brown.