One Rep Max Calculator

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Formula

Epley: 1RM = w × (1 + r ÷ 30); Brzycki: 1RM = w × 36 ÷ (37 − r); Lombardi: 1RM = w × r^0.10; estimate = average of the three

1RM: estimated one-repetition maximum, in the same unit as the weight lifted
w: weight lifted in the set (lb or kg)
r: number of reps completed with good form, 1 to 20

What a one rep max calculator tells you

Your one-repetition maximum (1RM) is the heaviest weight you can lift once with good form. It is the standard measure of absolute strength, and most strength programs set their loads as a percentage of it. Testing a true max is tiring and carries more injury risk than ordinary training, so lifters usually estimate it from a heavier set of a few reps instead.

This one rep max calculator does that estimate for you. Enter the weight and the number of reps you completed, and it returns:

An estimated 1RM, the average of three published formulas.
Each formula’s answer (Epley, Brzycki and Lombardi), so you can see how much they agree.
A training table from 100% down to 50% of your 1RM, rounded to 5 lb or 2.5 kg plates.
The working, with your numbers substituted into each equation.

How to use the calculator

Warm up, then pick a weight you expect to lift for roughly 3 to 8 reps.
Do as many clean reps as you can and stop when the next rep would break form.
Enter the weight, choose pounds or kilograms, and enter the reps you completed.
Read the average estimate, then check the formula rows. If they are far apart, your set was probably too long.

Run it separately for each lift. A one rep max calculator for bench press needs a bench set; squat and deadlift numbers come from their own sets, because rep endurance differs between exercises.

The one rep max formulas

All three equations scale the weight you lifted by a factor that grows with the number of reps.

Epley (1985): 1RM = w × (1 + r ÷ 30). Each extra rep adds about 3.3% of the weight.
Brzycki (1993): 1RM = w × 36 ÷ (37 − r). Slightly more conservative than Epley below 10 reps; the two meet exactly at 10.
Lombardi (1989): 1RM = w × r^0.10. A power curve that rises more slowly, so it gives higher estimates at low reps and lower ones at high reps than the other two.

Averaging the three reduces the bias of any single equation. LeSuer and colleagues tested seven equations on bench press, squat and deadlift and found that accuracy is good at low reps, worsens as reps rise, and that every equation underestimated the deadlift.

Calculating a one rep max by hand

Say you squat 225 lb for 3 reps.

Epley: 225 × (1 + 3 ÷ 30) = 225 × 1.1 = 247.5 lb.
Brzycki: 225 × 36 ÷ (37 − 3) = 8,100 ÷ 34 = 238.2 lb.
Lombardi: 225 × 3^0.10 = 225 × 1.1161 = 251.1 lb.
Average: (247.5 + 238.2 + 251.1) ÷ 3 = 245.6 lb.

A sensible first attempt at a tested max would be around 240 lb, with 245 lb as the second attempt if the first moves well.

One rep max chart: reps vs. % of 1RM

Each formula can be turned around to show what share of your max you can lift for a given number of reps. The table below was computed from the same equations the calculator uses.

Reps to failure	Epley	Brzycki	Lombardi
2	93.8%	97.2%	93.3%
3	90.9%	94.4%	89.6%
4	88.2%	91.7%	87.1%
5	85.7%	88.9%	85.1%
6	83.3%	86.1%	83.6%
8	78.9%	80.6%	81.2%
10	75.0%	75.0%	79.4%
12	71.4%	69.4%	78.0%

Up to about 8 reps the equations stay within 3 to 4 percentage points of each other. By 12 reps they disagree by almost 9 points, which is why the calculator adds a warning on long sets.

Putting your estimate to use

Setting training loads. Many programs work at 70% to 85% of 1RM for sets of 5 to 12. Use the percentage table under the result instead of guessing.
Tracking progress without max testing. Re-run the calculator every few weeks with a hard set of 3 to 5 reps. A rising estimate shows strength gains without the fatigue of a true max attempt.
Planning a meet or test day. The estimate gives a reasonable opener and second attempt.
Fueling heavier training. Strength blocks raise energy and protein needs; the macro calculator and TDEE calculator help you set intake.
Switching units. If your gym’s plates are in kilograms but your log is in pounds, convert with the kg to lbs converter.

Common mistakes

Leaving reps in reserve. The formulas assume the set ended at failure. Stopping two reps early makes the estimate roughly 5% to 7% too low.
Using very long sets. Sets of 15 or 20 measure endurance more than strength. Above 12 reps, treat the result as rough.
Counting sloppy reps. Bounced, half-depth or assisted reps inflate the estimate.
Comparing across exercises. A bench press estimate tells you nothing about your squat.
Testing when fatigued. A set at the end of a hard session underestimates what you could do fresh.

Glossary

1RM (one-repetition maximum). The most weight you can lift once with correct technique.
Reps to failure. Repetitions completed until another full rep is not possible.
%1RM. A training load expressed as a percentage of your one rep max.
RPE / reps in reserve. Ways of rating how close to failure a set was; this calculator assumes zero reps in reserve.

Worked examples

Bench press, 5 reps in pounds

175 lb pressed for 5 reps to failure.

Inputs: Weight lifted = 175; Weight unit = Pounds (lb); Reps completed = 5

Epley: 175 × (1 + 5 ÷ 30) = 204.2 lb Brzycki: 175 × 36 ÷ (37 − 5) = 196.9 lb Lombardi: 175 × 5^0.10 = 205.6 lb Average = (204.17 + 196.88 + 205.56) ÷ 3 = 202.2 lb

Answer: 175 lb × 5 reps → estimated 1RM 202.2 lb (average of Epley, Brzycki and Lombardi).

Squat, 8 reps in kilograms

100 kg squatted for 8 reps.

Inputs: Weight lifted = 100; Weight unit = Kilograms (kg); Reps completed = 8

Epley: 100 × (1 + 8 ÷ 30) = 126.7 kg Brzycki: 100 × 36 ÷ (37 − 8) = 124.1 kg Lombardi: 100 × 8^0.10 = 123.1 kg Average = (126.67 + 124.14 + 123.11) ÷ 3 = 124.6 kg

Answer: 100 kg × 8 reps → estimated 1RM 124.6 kg (average of Epley, Brzycki and Lombardi).

Edge case: a single rep

A true single is already a one-rep max, so every formula returns the weight lifted.

Inputs: Weight lifted = 140; Weight unit = Kilograms (kg); Reps completed = 1

Epley: 140 × (1 + 1 ÷ 30) = 140 kg Brzycki: 140 × 36 ÷ (37 − 1) = 140 kg Lombardi: 140 × 1^0.10 = 140 kg Average = (140 + 140 + 140) ÷ 3 = 140 kg

Answer: 140 kg × 1 reps → estimated 1RM 140 kg (average of Epley, Brzycki and Lombardi).

Assumptions and limitations

This is an estimate, not medical advice. Real one-rep maxes vary with technique, fatigue, the exercise and training history, and can differ from the prediction by several percent.
The set is assumed to be taken to (or very close to) failure. Stopping with reps in reserve makes every formula underestimate your max.
The headline result is the simple average of the Epley, Brzycki and Lombardi formulas. A single rep is treated as a 1RM, so all three return the weight lifted.
Reps are whole numbers from 1 to 20. Above 12 reps the formulas diverge and the calculator adds a note; 10 reps or fewer give the most reliable estimates.
Training loads are rounded to 5 lb or 2.5 kg steps to match common plate increments.
If you have an injury, a heart condition or are new to lifting, get advice from a doctor or qualified coach before heavy or to-failure sets.

Frequently asked questions

How do you calculate one rep max?

Lift a weight you can handle for 3 to 10 clean reps, stop at failure, then plug weight and reps into a formula. With Epley, 1RM = weight × (1 + reps ÷ 30), so 200 lb for 6 reps gives 200 × 1.2 = 240 lb.

Are one rep max calculators accurate?

For sets of about 10 reps or fewer they usually land within a few percent of a tested max. Accuracy drops at higher reps, for lifters with unusual endurance, and when the set was not truly taken to failure.

What is the Brzycki formula?

Matt Brzycki's 1993 equation is 1RM = weight × 36 ÷ (37 − reps), the same as weight ÷ (1.0278 − 0.0278 × reps). It is slightly more conservative than Epley below 10 reps, and the two agree exactly at 10 reps.

Which formula is most accurate?

No single equation wins for every lift. Studies comparing them found Brzycki and Epley close for bench press and squat at low reps, while all equations tended to underestimate the deadlift. Averaging three formulas smooths out their individual biases.

Can I use the calculator for bench press, squat and deadlift?

Yes. The formulas only use the weight and the reps, so they work for any barbell or machine lift. Use a separate set for each exercise, because your rep endurance differs between lifts.

How many reps should I do to estimate my max?

Three to six reps is a good compromise between safety and accuracy. Singles and doubles are close to a true max already, while sets of 12 or more mostly measure muscular endurance.

How do I use my 1RM for training?

Programs prescribe loads as a percentage of 1RM, for example 80% for sets of about 6 to 8 reps or 70% for sets of 10 to 12. The table under the result lists 50% to 100% of your estimate, rounded to loadable weights.

Sources

Strength Testing—Predicting a One-Rep Max from Reps-to-Fatigue — Journal of Physical Education, Recreation & Dance (Brzycki, 1993), Taylor & Francis. Checked October 10, 2026.
The Accuracy of Prediction Equations for Estimating 1-RM Performance in the Bench Press, Squat, and Deadlift — Journal of Strength and Conditioning Research (LeSuer et al., 1997). Checked October 10, 2026.
Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry — Journal of Strength and Conditioning Research (Reynolds, Gordon & Robergs, 2006), via PubMed. Checked October 10, 2026.