How to Use the Calculator
Pick a recent set where you stopped because you couldn't do another rep with good form, or were within a rep of it. Enter the weight and the number of reps you completed.
- Use 3 to 10 reps. Heavier sets give better estimates, and above 10 reps the estimate gets less reliable.
- Count only clean reps. A rep you ground out with broken form doesn't count.
- Use one lift at a time. Your bench press and squat have different maxes, so estimate each from its own set.
How the One Rep Max Formula Works
The calculator uses the formula Matt Brzycki published in 1993 (Brzycki, 1993):
1RM = weight ÷ (1.0278 − 0.0278 × reps)
For example, 185 lb for 5 reps gives 185 ÷ 0.889, an estimated 1RM of about 208 lb. Read the other way, the same line gives the rep max chart: the share of your 1RM you can lift for a given number of reps.
The other common formula is Epley's: 1RM = weight × (1 + reps ÷ 30). The two agree at 10 reps and stay close below that, with Epley a little higher:
| Set | Brzycki | Epley |
|---|---|---|
| 185 lb × 3 | 196 lb | 204 lb |
| 185 lb × 5 | 208 lb | 216 lb |
| 185 lb × 8 | 230 lb | 234 lb |
| 185 lb × 10 | 247 lb | 247 lb |
Neither one is right for everyone. What matters most is using the same formula every time, so changes in the number reflect changes in your strength.
Rep Max Chart
Each row is the share of your 1RM you can typically lift for that many reps, from the Brzycki formula. The last two columns show it for a 1RM of 200 lb and of 100 kg.
| Reps | % of 1RM | 1RM 200 lb | 1RM 100 kg |
|---|---|---|---|
| 1 | 100% | 200 lb | 100 kg |
| 2 | 97% | 194 lb | 97 kg |
| 3 | 94% | 189 lb | 94 kg |
| 4 | 92% | 183 lb | 92 kg |
| 5 | 89% | 178 lb | 89 kg |
| 6 | 86% | 172 lb | 86 kg |
| 8 | 81% | 161 lb | 81 kg |
| 10 | 75% | 150 lb | 75 kg |
| 12 | 69% | 139 lb | 69 kg |
| 15 | 61% | 122 lb | 61 kg |
Real people vary around these numbers: some can do more reps at a given percentage than others, and the pattern differs between exercises. Treat the chart as a starting point for picking weights.
How Accurate Is an Estimated 1RM?
Treat it as an estimate: it's most useful when the set was heavy and close to failure. In a study of 70 adults aged 18 to 69, a 5-rep max predicted bench press and leg press 1RM better than a 10- or 20-rep max did, and the authors advised using no more than 10 reps in simple prediction equations like this one (Reynolds et al., 2006).
The estimate is less reliable when:
- The set wasn't close to failure. Stopping with three reps left makes your 1RM look lower than it is.
- You did more than 10 reps. The calculator flags this.
How to Use Your 1RM to Pick Training Weights
Once you know your 1RM, you can set loads by percentage instead of guessing. The American College of Sports Medicine recommends that beginners start with weights they can lift for 8 to 12 reps, and that more experienced lifters use a wider range of 1 to 12 reps, with more heavy work at 1 to 6 reps. When you can do one or two reps more than your target, add 2% to 10% to the weight (ACSM, 2009).
The same review found that muscle growth improved with higher weekly volume, 10 or more sets a week, and that power improved with moderate loads of 30% to 70% of 1RM. If you're training to keep muscle while losing weight, see our guide to protecting muscle on GLP-1 medications and how strength and cardio compare for weight loss.
Should You Test Your True 1RM?
Most people don't need to. An estimate from a hard set of 3 to 5 reps is close enough to plan training, and it carries less risk than a true max attempt. If you do test a max, warm up with gradually heavier singles, use a spotter or safety bars, and stop when your form changes.
Track Your Estimated 1RM in FITIV Pulse
Instead of doing the math after each workout, FITIV Pulse works out your estimated 1RM from the sets you log on iPhone or Apple Watch. When a set beats your best, FITIV flags an Estimated Max PR or Heaviest Weight PR on your watch and in your post-workout summary. Each exercise's history charts your One Rep Max over time, so you can see whether your strength is actually going up.
You can also log Reps in Reserve for each set, and use Apply Progressive Overload to get a suggested weight and reps for your next session based on your recent history.
Frequently Asked Questions
How do I calculate my one rep max without maxing out?
Do a hard set of 3 to 10 reps, stopping when you can't do another rep with good form. Divide the weight by (1.0278 − 0.0278 × reps), the Brzycki formula. For example, 185 lb for 5 reps works out to an estimated 1RM of about 208 lb.
Is the Brzycki or Epley formula more accurate?
Neither is consistently more accurate for everyone. They give the same answer at 10 reps, and Epley comes out a little higher with fewer reps: 216 lb versus 208 lb for 185 lb × 5. Pick one and stick with it, so changes in your number reflect changes in your strength.
How many reps should I use to estimate my 1RM?
Between 3 and 10. Estimates from heavier sets are more accurate: a study of bench press and leg press comparing 5-, 10- and 20-rep maxes found the 5-rep max predicted 1RM best and recommended using no more than 10 reps.
What percentage of my 1RM should I lift to build strength?
Research links bigger strength gains to heavier loads of at least 80% of your 1RM, roughly 8 reps or fewer, for 2 to 3 sets. Lighter loads build strength too, especially for beginners, who can start with weights they can lift 8 to 12 times. Whatever your level, add 2% to 10% once you can do one or two reps more than your target.
