How to use the one rep max calculator
- Choose the exercise and enter the weight you lifted, in kg or lb.
- Choose how many reps you completed with good form – a set taken close to failure gives the best estimate.
- Optionally add your body weight to see your strength-to-body-weight ratio.
- Press Calculate for your estimated 1RM, training weights for every rep range, and what each formula gives.
What is a one-rep max?
Your one-repetition maximum (1RM) is the heaviest weight you can lift once with correct technique. Training programmes set loads as a percentage of it – for example 5 sets of 5 at 80%. Testing a true 1RM is tiring and carries some injury risk, so most people estimate it from a lighter set of several reps.
1RM formulas
With w the weight lifted and r the reps completed:
| Formula | 1RM |
|---|---|
| Epley (1985) | w\,(1 + r/30) |
| Brzycki (1993) | w \times 36 / (37 - r) |
| Lander (1985) | 100w / (101.3 - 2.67123r) |
| Lombardi (1989) | w \times r^{0.10} |
| Mayhew (1992) | 100w / (52.2 + 41.9e^{-0.055r}) |
| O'Conner (1989) | w\,(1 + 0.025r) |
| Wathan (1994) | 100w / (48.8 + 53.8e^{-0.075r}) |
Each was fitted to a different group of lifters, so they agree closely at low reps and drift apart at high reps. The calculator shows the average of all seven, which is less sensitive to any one formula's bias.
Epley: 80 \times (1 + 8/30) = 101.3 kg. Brzycki: 80 \times 36/(37 - 8) = 99.3 kg. The seven formulas range from 96.0 to 102.1 kg, an average of 99.8 kg.
Percentage of 1RM chart
How many reps most people can do at each percentage of their one-rep max (based on the US National Strength and Conditioning Association's training load chart):
| % of 1RM | Reps | If 1RM is 100 kg | If 1RM is 225 lb |
|---|---|---|---|
| 100% | 1 | 100 kg | 225 lb |
| 95% | 2 | 95 kg | 215 lb |
| 93% | 3 | 93 kg | 210 lb |
| 90% | 4 | 90 kg | 205 lb |
| 87% | 5 | 87 kg | 195 lb |
| 85% | 6 | 85 kg | 190 lb |
| 83% | 7 | 83 kg | 185 lb |
| 80% | 8 | 80 kg | 180 lb |
| 77% | 9 | 77 kg | 175 lb |
| 75% | 10 | 75 kg | 170 lb |
| 70% | 11 | 70 kg | 160 lb |
| 67% | 12 | 67 kg | 150 lb |
| 65% | 15 | 65 kg | 145 lb |
Choosing a training weight
- Strength: 1–5 reps at 87–100% of 1RM, with longer rests (2–5 minutes).
- Muscle growth (hypertrophy): 6–12 reps at about 67–85%. Lighter loads taken close to failure also build muscle.
- Muscular endurance: 15 or more reps at 65% or less, with short rests.
Getting an accurate estimate
- Use a set of 3–8 reps taken close to failure; estimates from more than 10 reps are less reliable.
- Count only reps with full range of motion and good form.
- Warm up first, and use a spotter or safety bars for bench press and squat.
- Results differ between lifts and people: well-trained lifters often do fewer reps at a given percentage on squat and deadlift than on upper-body lifts.
For the energy side of training, see the calories burned calculator, and make sure you eat enough protein with the protein calculator.
Frequently asked questions
How do I calculate my one rep max?
Lift a weight for as many good reps as you can (ideally 3–8), then use a formula such as Epley: 1RM = weight × (1 + reps ÷ 30). 100 kg for 5 reps gives about 117 kg.
Which 1RM formula is most accurate?
Epley and Brzycki are the most widely used and are close for 2–10 reps. No single formula fits everyone, so the calculator averages seven.
What percentage of 1RM should I train at?
About 87–100% for strength (1–5 reps), 67–85% for muscle growth (6–12 reps) and 65% or less for endurance (15+ reps).
Is it safe to test my real 1RM?
For experienced lifters with good technique, a warm-up and a spotter, yes. Beginners are better off estimating it from a set of several reps.
How much should I bench for my body weight?
Many strength standards treat a bench press of about 1 × body weight as an intermediate level for men and about 0.6–0.7 × for women, but it varies widely with age, training and build.