OnSumoTools

One Rep Max (1RM) Calculator

Estimate your one rep max with five proven formulas and a percentage-based training table for programming workouts.

Your set

Unit

Estimated 1RM (average)

114.57 kg

Formula comparison

FormulaEstimated 1RM
Epley116.67 kg
Brzycki112.5 kg
Lander113.71 kg
Lombardi117.46 kg
O'Connor112.5 kg
Average114.57 kg

Training percentage table

%WeightEst. reps
50%57.29 kg20+
55%63.01 kg19
60%68.74 kg17
65%74.47 kg15
70%80.2 kg12
75%85.93 kg10
80%91.66 kg8
85%97.38 kg5
90%103.11 kg3
95%108.84 kg2
100%114.57 kg1

For heavy squats and deadlifts, many lifters use a belt and longer rest above 90% of estimated max.

These are estimates, not medical advice. Stop if you feel pain, dizziness, or loss of form.

How does the One Rep Max Calculator work step by step?

The calculator applies five published formulas to your lifted weight (w kg or lb) and rep count (r), each modeling the fatigue curve differently. Epley: 1RM = w × (1 + r ÷ 30). Brzycki: 1RM = w × 36 ÷ (37 − r). Lander: 1RM = (100 × w) ÷ (101.3 − 13.36 × r). Lombardi: 1RM = w × r^0.10. O'Connor: 1RM = w × (1 + r ÷ 40). It then averages all five and builds a percentage table showing the estimated load for 50%–100% of your calculated 1RM, useful for programming warm-up sets. Key assumption: all formulas assume sub-maximal reps performed to failure or near-failure with full range of motion. Edge case: accuracy drops sharply above 10 reps because no formula reliably models the aerobic contribution that kicks in at higher rep ranges. For rep counts above 10, treat the estimate as a rough lower bound only. Beginners whose technique degrades before muscular failure will also see inflated 1RM estimates.

What does a typical One Rep Max Calculator result look like?

| Formula | Calculation | Estimated 1RM | |---|---|---| | Epley | 100 x (1 + 5/30) | 116.7 kg | | Brzycki | 100 x (36 / 32) | 112.5 kg | | Lander | (100 x 100) / (101.3 - 13.36) | 113.8 kg | | Lombardi | 100 x 5^0.10 | 116.7 kg | | O'Connor | 100 x (1 + 5/40) | 112.5 kg | | Average | | 114.4 kg |

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Frequently asked questions

  • Which 1RM formula is most accurate?

    No formula is universally most accurate, results vary by individual, by lift, and by training background. Epley and Brzycki are the two most commonly cited in strength research. Averaging all five reduces the impact of any one formula's individual bias. If you periodically test your true 1RM, you can compare actual results to formula estimates and identify which formula tends to be closest for you specifically.

  • Is it safe to test a true 1RM?

    Testing a true one rep max carries injury risk, particularly for lifters with less than one to two years of consistent training, and requires a thorough warm-up, a spotter for squat and bench press, and near-perfect technique under maximum load. Most coaches recommend estimating from 3-5 rep sets at submaximal loads. The accuracy difference is small enough that estimated 1RMs from well-executed sets are suitable for all practical programming.

  • How do I use the training percentage table?

    Match the intensity percentage to your training goal for the week. Strength work typically uses 85-95% of 1RM for sets of 1-5 reps. Hypertrophy work sits at 65-80% for 6-12 reps. Speed and technique work often uses 50-65% to allow maximum bar speed. Use the table to select the working weight directly rather than calculating percentages by hand before each session.

  • Why do the five formulas give different numbers?

    Each formula was derived from a different dataset and population. Epley and Lombardi are generous estimators; Brzycki and O'Connor are more conservative. The divergence is typically within 5% for sets of 3-8 reps, which is within acceptable training margin. Averaging them gives a middle estimate that is less likely to lead to loading errors in either direction.

  • What is the difference between a tested 1RM and an estimated 1RM for programming purposes?

    A tested 1RM is a weight you have actually lifted once under controlled conditions with proper warm-up and technique. An estimated 1RM is derived from a submaximal performance using one of the formulas. For most training contexts the distinction does not matter much, programming at 80% of an estimated 1RM produces similar training stimulus to programming at 80% of a tested 1RM, assuming the estimate is reasonably accurate. The tested value may be slightly higher than the estimate because near-maximal neural drive is not fully captured by submaximal rep formulas. If you find your training percentages consistently feel lighter than they should, your actual 1RM may be higher than the estimate.

  • How do I warm up when working at a high training percentage?

    A standard warm-up protocol for working at 85-95% of 1RM: start with an empty or light bar for 8-10 reps, then add weight in increments of 15-20% of your working weight, reducing reps as you approach the working set. Common warm-up sets: 40%, 55%, 70%, 80% of 1RM for 5, 4, 3, 2 reps respectively, then the working set. The training table in this calculator shows the weight for each percentage increment, making it straightforward to read off the bar load for each warm-up step without doing mental arithmetic between sets.

Estimate your max without risking it

Your one rep max is the heaviest weight you can lift for a single clean rep. Testing it for real is hard on your body and a bit risky. You can get a solid estimate from a lighter set instead.

Enter the weight you lifted and how many reps you got. The calculator estimates your 1RM with five formulas and averages them.

Five formulas, five answers

Epley, Brzycki, Lander, Lombardi and O'Connor all turn weight and reps into a max. They differ because each was fitted to different lifters and lifts. At low reps, say 3 to 5, they agree closely. As reps climb past ten, the numbers spread out and accuracy drops.

No formula wins in every case. The average smooths out their biases, which is why the tool shows it. Use sets of 10 reps or fewer if you can.

Estimated versus tested

A tested 1RM is the real thing. An estimate is a prediction. For programming, the estimate works well enough, since you only need a number to set percentages from. Retest every few weeks or after a block of training and update.

Is testing a true max safe? It can be, with a spotter, a proper warm-up and good form. Beginners and anyone with joint trouble should skip it and use estimates.

The percentage table

Once you have a 1RM, the table shows the weight for each percentage from 50 to 100. Lighter percentages suit higher reps and technique work. Around 70 to 85 percent is a common zone for building strength and size. Above 90 percent is heavy and used sparingly.

If your 1RM is 100 kg, 80 percent is 80 kg. Pick the weight, do the planned reps and keep a note of how it felt.

Warming up for heavy work

Start with an empty bar or light weight for easy reps. Build up in a few steps, dropping the reps as the weight increases. Something like 50 percent for 8 reps, 70 percent for 3, 85 percent for 1, then your working sets. Rest long enough that you're fresh for the heavy sets, and keep the warm-up from tiring you out.

The numbers stay in your browser. Always lift with a spotter or safety bars when pushing heavy.