Calculate your one-repetition maximum for any exercise using 10 different formulas. Generate a full training percentage table.
Your one rep max (1RM) is the heaviest weight you can lift for a single repetition of an exercise with good form. Rather than testing it directly, a 1RM calculator estimates it from a lighter weight and the number of reps you complete. For example, lifting 100 kg for 5 reps gives an estimated 1RM of about 113–117 kg, depending on the formula used.
| Formula | 1RM (kg) |
|---|
| % | Weight (kg) | Reps (est.) | Zone |
|---|
A 1RM calculator uses a prediction formula based on the weight you lifted and how many reps you managed. The two most common are Epley and Brzycki.
Once you know your 1RM, coaches use percentages of it to program training. This chart shows the load and the reps you can typically perform at each percentage.
| % of 1RM | Typical Reps | Training Purpose |
|---|---|---|
| 100% | 1 | Maximal strength / testing |
| 95% | 2 | Strength |
| 90% | 3–4 | Strength |
| 85% | 5–6 | Strength / power |
| 80% | 7–8 | Strength / hypertrophy |
| 75% | 8–10 | Hypertrophy |
| 70% | 10–12 | Hypertrophy |
| 65% | 12–15 | Muscular endurance |
| 60% | 15–20 | Endurance |
| 50% | 20+ | Warm-up / endurance |
See our 1RM Percentage Chart for a fuller reference to training loads and approximate rep ranges, including metric and imperial worked examples.
An estimated 1RM from a calculator is a safe, convenient guide. A tested 1RM — actually lifting your maximum — is more precise but riskier and more fatiguing. For most people, the estimate is more than accurate enough for programming.
| Feature | Estimated 1RM | Tested 1RM |
|---|---|---|
| Safety | High — uses submaximal loads | Higher risk — maximal load |
| Accuracy | Very good at low reps | Exact on the day |
| Best for | Most lifters, regular tracking | Experienced lifters, competition |
If you do test a true 1RM, do it carefully:
Beginners are usually better off using an estimated 1RM until their technique is well established.
Estimate your 1RM from a submaximal lift (best accuracy with 1–6 reps). Use the result to set training loads based on percentage of 1RM.
| %1RM | Reps | Training goal |
|---|---|---|
| 90–100% | 1–3 | Max strength |
| 80–90% | 3–5 | Strength |
| 70–80% | 6–10 | Strength-hypertrophy |
| 60–70% | 10–15 | Hypertrophy/endurance |
| 50–60% | 15–20 | Muscular endurance |
The One Rep Max (1RM) is the maximum weight a person can lift for one complete repetition with proper form. It is the gold standard for measuring absolute strength in resistance training. Rather than directly testing a true 1RM (which carries injury risk), the calculator estimates it from a submaximal performance — a weight you can lift 2-10 times.
| Formula | Equation | Most Accurate For |
|---|---|---|
| Epley (most common) | weight × (1 + reps/30) | Reps 1-10 |
| Brzycki | weight × (36/(37 − reps)) | Reps 1-10 |
| Lander | weight × (100/(101.3 − 2.67123 × reps)) | Reps 2-14 |
| Lombardi | weight × reps^0.10 | Higher rep ranges |
| Goal | % of 1RM | Rep Range | Sets |
|---|---|---|---|
| Strength (max force) | 85–100% | 1–5 reps | 3–5 sets |
| Hypertrophy (muscle size) | 65–85% | 6–12 reps | 3–4 sets |
| Muscular endurance | 50–65% | 15–25 reps | 2–3 sets |
| Power (speed-strength) | 30–70% | 1–5 reps (fast) | 3–5 sets |
These percentages are a fixed-target approach. If you'd rather select load by how a set actually feels — adjusting for daily fatigue and readiness — see our RPE Calculator, which can also estimate a working weight or an RPE-adjusted 1RM.
How accurate is the 1RM calculator?
1RM estimation formulas are most accurate when the rep count is 10 or fewer. At higher rep ranges (12-20+), accuracy decreases significantly because fatigue, not strength, limits performance. For best accuracy, use a weight you can lift 4-8 times with perfect form. The Epley formula typically estimates within 5-10% of a true tested 1RM.
What percentage of 1RM should I train at?
For muscle building (hypertrophy): train at 65-85% of 1RM for 6-12 reps. For maximal strength: 85-100% for 1-5 reps. For muscular endurance: 50-65% for 15+ reps. Research shows hypertrophy occurs across a wide rep range if sets are taken close to failure — the percentage of 1RM matters less than training effort level (RPE).
Should beginners test their 1RM?
Beginners should focus on technique for 3-6 months before testing 1RM. The injury risk of maximal attempts is higher when form is not yet automatic. Use the calculator with 8-10 rep efforts instead. As you progress, periodically test estimated 1RM every 4-6 weeks to track strength gains and adjust training weights.
How do I calculate my one rep max?
Enter the weight you lifted and the number of reps you completed into the calculator, and it applies proven formulas like Epley and Brzycki to estimate your 1RM. For example, 100 kg for 5 reps gives roughly 113–117 kg. You do not need to attempt a true maximal lift.
How accurate is a one rep max calculator?
Very accurate at low rep counts (about 1–6 reps), usually within a few percent of a tested max. Above 10 reps, estimates become less reliable because endurance starts to influence the result. For the best estimate, use a set taken close to failure at 3–6 reps.
What is the best 1RM formula?
No single formula is best for everyone. Epley and Brzycki are the most popular and give very similar results at low reps. This calculator averages several formulas for a balanced estimate. Differences between them are usually small — a few kilograms at most.
How do I use my 1RM for training?
Coaches program lifts as a percentage of your 1RM. Roughly, 80–95% builds strength, 65–80% builds muscle size, and below 65% builds endurance. For example, if your 1RM is 100 kg, a hypertrophy set might use 70–75 kg for 8–12 reps. See the percentage chart above.
Should beginners test their one rep max?
Usually not. Beginners are better off using an estimated 1RM from lighter sets while they build technique. Testing a true maximum carries injury risk if form is not yet solid. Once you have several months of consistent, well-coached training, occasional testing can be appropriate.
How often should I retest my 1RM?
Every 8–12 weeks is plenty for most lifters, or at the end of a training block. Testing or estimating too often adds fatigue and does not give strength enough time to improve meaningfully. Tracking estimated 1RM from your regular sets is a low-risk alternative.
Is one rep max different for men and women?
The way you calculate and use 1RM is identical, but absolute numbers differ due to differences in muscle mass. What matters for training is your own 1RM and the percentages you work at, not comparison to anyone else. Everyone progresses from their individual baseline.