1RM Calculator: Estimate Your One-Rep Max
Free 1RM calculator: enter one hard set to estimate your one-rep max, see how far six formulas spread, and turn the number into training weights.
The calculator measures your max. The diagnosis explains why it stopped moving.
Bar included.
Clean reps, taken close to failure.
Will this number move? Save it and check back in 4 weeks: the check tells you whether it is still climbing or has stalled. No email needed.
| Formula | Equation | 1RM (lb) |
|---|---|---|
| Epley | w × (1 + r ÷ 30) | 262.5 |
| Brzycki | w × 36 ÷ (37 − r) | 253.1 |
| Lombardi | w × r^0.10 | 264.3 |
| O'Conner | w × (1 + 0.025 × r) | 253.1 |
| Mayhew | w ÷ (0.522 + 0.419 × e^(−0.055 × r)) | 267.8 |
| Wathen | w ÷ (0.488 + 0.538 × e^(−0.075 × r)) | 262.3 |
w = weight lifted, r = reps. At 1 rep we return the weight for every formula.
| % 1RM | Load (lb) | ≈ Reps |
|---|---|---|
| 100% | 260 | 1 |
| 95% | 245 | 2 |
| 90% | 230 | 3 |
| 85% | 220 | 5 |
| 80% | 205 | 8 |
| 75% | 195 | 10 |
| 70% | 180 | 13 |
| 65% | 170 | 16 |
| 60% | 155 | 20 |
| 55% | 140 | 25 |
| 50% | 130 | 30 |
Loads rounded to the nearest 5 lb. Reps come from the Epley formula solved for reps, r = 30 × (100 ÷ % − 1); past about 12 reps they vary a lot from person to person.
Sources: One-repetition maximum formulas (Wikipedia); Mayhew et al. 2008, J Strength Cond Res — prediction equations are more accurate under 10 reps.
Numbers not moving for weeks? Find out why- Updated
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A 1RM calculator turns one hard set into an estimate of the heaviest single you could lift today. Enter the weight and the clean reps, ideally 3–6 reps that ended a rep or two short of failure. The headline averages Epley and Brzycki; the table shows four more formulas so you see the spread. Use it to set training weights and track progress, not as a record.
How do you use the 1RM calculator?
Enter the full load with the bar, the reps you finished with clean form, and your unit. Use your hardest set of the day, not a warm-up, and keep it to 10 reps or fewer.
- Sets of 3–6 reps estimate best. In 70 adults, 5-rep maxes predicted bench and leg press maxes more accurately than 10- or 20-rep maxes, and the authors advise against using more than 10 reps in linear formulas (Reynolds et al., 2006).
- One exercise at a time: a squat set predicts a squat max, not a leg press max.
- Stopped with reps to spare? The estimate will run low; rate the set with the RPE calculator instead.
Which formula does the calculator use?
The headline is the average of two classic equations: Epley, weight × (1 + reps ÷ 30), and Brzycki, weight × 36 ÷ (37 − reps). They agree at 10 reps; below that, Epley reads a little higher (one-rep max formulas).
For 225 lb (102 kg) × 5, Epley gives 262.5 lb, Brzycki 253.1 lb, and the headline is 257.8 lb. Averaging is deliberate: across 220 men, Brzycki was the most accurate equation for sets of 10 or fewer, and the authors noted that the average of two equations may reduce the error (Mayhew et al., 1995).
How accurate is an estimated one-rep max?
Accurate enough to train from, not to bet a meet on. In a classic validation study, predicted and tested maxes correlated above r = 0.95 for the bench, squat and deadlift, yet every formula underestimated the deadlift (LeSuer et al., 1997).
| Lift | Miss in that study | How to read your estimate |
|---|---|---|
| Bench press | Up to 6% low; Epley about 1% | Close to your true max |
| Squat | 2–8% low | A slightly conservative floor |
| Deadlift | 9–14% low | Your real single is likely higher |
If you can grind out far more reps than most people, expect a high reading: at 70% of max, endurance runners managed about 40 leg press reps, weightlifters about 18 (Richens & Cleather, 2014).
How should you use your 1RM in training?
Multiply it by a percentage to choose working weights, then re-estimate from one top set each week. Judge the trend over three or four weeks, never a single day.
| % of 1RM | Reps you can usually do | Typical use |
|---|---|---|
| 90% | About 4 | Heavy triples |
| 85% | About 6 | Strength sets of 5 |
| 80% | About 8 | Strength and size |
| 75% | About 10 | Hypertrophy sets |
Rep counts follow the NSCA training load chart (NSCA). For every percentage at your own max, use the 1RM percentage chart.
What if your estimated max stops going up?
Three flat weeks of normal training is a stall, and no formula can tell you why. Often more than one cause is at work, so guessing a single fix rarely works.
Some slowdown is normal: among 1,271 male powerlifters, the strongest improved about half as fast as the least strong, 0.102 versus 0.211 kg a day (Latella et al., 2020). LiftDecode's rule: rule out the boring causes first. No rule for adding weight, sets that end too early, too little practice, recovery that cannot keep up. Not sure which are yours? Find out what is holding your max back.
FAQ
Is Epley or Brzycki more accurate?
Neither wins everywhere. They match at 10 reps, and Epley reads a few percent higher below that. The best equation changes by lift and lifter, so read the two as a range and trust sets of 3–6 hard reps most.
How many reps should I use to estimate my 1RM?
Three to six reps close to failure, never more than 10. Five-rep maxes predicted the true max best in the 2006 study, and accuracy drops as reps climb because endurance starts to matter.
Why does the calculator underestimate my deadlift?
It is a known pattern: in the 1997 validation study every formula came in 9–14% low on the deadlift, while bench estimates landed within a few percent. Treat a deadlift estimate as a floor and test a heavy triple if you need a precise number.
How often should I test a true one-rep max?
Rarely. Estimate from normal top sets every week or two and watch the trend. Test a true single before a meet or a percentage-based program; a max-out day proves strength instead of building it.
Written and maintained by LiftDecode. Training and nutrition education for healthy adults, not medical advice — if you have a health condition or an injury, talk to a professional who can examine you.