How to use this calculator
Choose pounds or kilograms, then enter the weight you lifted and the number of reps you completed, from 1 to 12. Use a set you took close to failure with good form: the formulas assume you couldn’t have done another rep.
You’ll see:
- your estimated one-rep max, the average of three formulas
- each formula’s estimate on its own, and how far apart they are
- what percentage of your 1RM your set was
- a training load chart from 100% down to 50% of your 1RM, with the reps you could typically do at each load
The formulas
All three formulas estimate your 1RM from the weight (w) and reps (r) of a single set.
Epley (1985):
Brzycki (1993):
Lombardi (1989):
A single rep is already a one-rep max, so for 1 rep the calculator returns the weight itself. (Taken literally, Epley would add 3%.)
The rep estimates in the training chart come from turning the Epley and Brzycki equations around to solve for reps at each percentage, then taking the midpoint of the two. At 75% of 1RM both give exactly 10 reps.
Worked example
You bench pressed 185 lb for 5 reps:
- Epley: 185 × (1 + 5 ÷ 30) = 216 lb
- Brzycki: 185 × 36 ÷ (37 − 5) = 208 lb
- Lombardi: 185 × 5^0.10 = 217 lb
- Average: (215.8 + 208.1 + 217.3) ÷ 3 = 214 lb
So your 185-lb set was about 87% of your estimated max. From the chart, a working set at 80% would be 171 lb for about 8 reps, and 90% would be 192 lb for about 4.
How the formulas compare
This table shows each formula’s estimate as a multiple of the weight lifted, which is the same as the 1RM for a 100-lb set.
| Reps | Epley | Brzycki | Lombardi | Average |
|---|---|---|---|---|
| 2 | 106.7 | 102.9 | 107.2 | 105.6 |
| 3 | 110.0 | 105.9 | 111.6 | 109.2 |
| 4 | 113.3 | 109.1 | 114.9 | 112.4 |
| 5 | 116.7 | 112.5 | 117.5 | 115.5 |
| 6 | 120.0 | 116.1 | 119.6 | 118.6 |
| 8 | 126.7 | 124.1 | 123.1 | 124.6 |
| 10 | 133.3 | 133.3 | 125.9 | 130.9 |
| 12 | 140.0 | 144.0 | 128.2 | 137.4 |
The formulas stay within a few percent of each other up to about 8 reps. By 12 reps they’re more than 15 percentage points apart, because Brzycki rises steeply while Lombardi flattens out. That spread is one reason the estimates get less trustworthy with longer sets.
Accuracy above 10 reps
Every rep-based formula assumes a fixed relationship between how heavy a weight is and how many times you can lift it. That holds reasonably well for short sets, but the more reps you do, the more the result depends on muscular endurance, technique and fatigue, which vary a lot from person to person and from lift to lift.
A 2006 study by Reynolds, Gordon and Robergs compared predictions from 5-, 10- and 20-rep sets against measured 1RMs on the chest press and leg press. The 5-rep data gave the most accurate predictions, and the authors concluded that no more than 10 reps should be used in these equations. That’s why this calculator stops at 12 reps and flags any set over 10.
For your best estimate:
- Pick a weight you can lift 3 to 8 times.
- Go close to failure with good form; stopping well short makes the estimate too low.
- Test when fresh, at the start of a session after a warm-up.
- Recheck every few weeks as you get stronger.
Using percentages in your training
Once you know your 1RM, you can set loads as a percentage of it. The American College of Sports Medicine’s 2009 position stand on resistance training recommends:
| Goal | Recommended loading |
|---|---|
| Strength, beginners | Loads you can lift 8 to 12 times |
| Strength, intermediate and advanced | 1 to 12 reps, periodized, with emphasis on 1 to 6 |
| Muscle size (hypertrophy) | 1 to 12 reps, with emphasis on 6 to 12 |
| Muscular endurance | 40% to 60% of 1RM for more than 15 reps |
In the calculator’s chart, 6 to 12 reps corresponds to roughly 70% to 85% of your 1RM. The rep counts are typical values: some people can do many more reps at 60% than the chart suggests, especially on leg exercises.
Strength training pairs well with good nutrition. The macro calculator sets protein, carb and fat targets, and the body fat calculator helps you track changes in body composition that the scale alone can miss.
Assumptions and limitations
- The same formulas are used for every exercise, but lifts differ in how many reps you can do at a given percentage, so an estimate for one lift may be less accurate than for another.
- They assume the set was taken close to failure with consistent form.
- Estimates are for healthy adults; they don’t account for age, training history or injury.
Sources
- Epley B. Poundage Chart. Boyd Epley Workout. Lincoln, NE: Body Enterprises; 1985.
- Brzycki M. Strength testing: predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance. 1993;64(1):88–90.
- Lombardi VP. Beginning Weight Training: The Safe and Effective Way. Dubuque, IA: W.C. Brown; 1989.
- Reynolds JM, Gordon TJ, Robergs RA. Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry. J Strength Cond Res. 2006;20(3):584–592.
- American College of Sports Medicine. Position stand: progression models in resistance training for healthy adults. Med Sci Sports Exerc. 2009;41(3):687–708.
These are estimates for healthy adults planning their training. Lift with good form and a spotter for heavy sets, and check with a doctor or qualified coach if you have an injury or health condition.
Frequently asked questions
What is a one-rep max?
Your one-rep max (1RM) is the heaviest weight you can lift for a single complete repetition of an exercise with good form. Coaches and training programs use it to set loads as a percentage, for example 3 sets of 5 at 80% of 1RM. Estimating it from a lighter set avoids the fatigue and injury risk of a true maximum attempt.
How do you calculate your one-rep max?
Lift a weight for as many good reps as you can, then plug the weight and reps into a formula. With the Epley formula, 185 lb for 5 reps gives 185 × (1 + 5 ÷ 30) ≈ 216 lb. This calculator also runs the Brzycki and Lombardi formulas and averages all three, which gives 214 lb for that set.
Which one-rep max formula is most accurate?
None is best for everyone or every lift. The formulas agree closely for sets of about 2 to 8 reps and drift apart after that, with Lombardi giving lower estimates at higher reps. Averaging them smooths out the differences, and the more reps you use, the less accurate any of them becomes.
Why does accuracy drop above 10 reps?
Long sets depend more on muscular endurance, which varies a lot between people and between exercises. A 2006 study in the Journal of Strength and Conditioning Research found that 5-rep sets gave the most accurate predictions and recommended using no more than 10 reps in these equations. For the best estimate, use a weight you can lift 3 to 8 times.
How much should I lift for strength or muscle growth?
The American College of Sports Medicine recommends that beginners use loads they can lift 8 to 12 times. More experienced lifters can work across 1 to 12 reps, emphasizing 1 to 6 reps for maximal strength and 6 to 12 for muscle size. For muscular endurance, it suggests 40% to 60% of 1RM for more than 15 reps.
Should I test my true one-rep max?
Beginners rarely need to, because an estimate is accurate enough to set training loads. If you do test it, warm up thoroughly, work up in a few heavier singles, use a spotter or safety bars, and stop if your form breaks down.
Updated November 2026. Results are estimates for educational purposes and depend on the inputs you provide.