1 Rep Max Calculator

Q: What is the most accurate 1 rep max formula?

No single formula wins for every lift. Wathan and Mayhew were most accurate for the bench, Wathan for the squat, and every formula underestimated the deadlift, so the best approach is to blend formulas by lift.

Q: Why is my deadlift estimate lower than my real max?

In research, every 1RM formula came in 9–14% low on the deadlift because lifters can grind out a heavier single than their rep sets suggest.

For CrossFit lifts and the strict pull-up

Enter a weight and the reps you did with it to estimate your 1-rep max. Seven research formulas are blended for each lift, with a percentage chart for programming your training.

Your set

Weight lifted

Reps1 to 10, taken close to failure

Use a set you took to failure or within a rep of it. Sets of 2–5 reps give the most accurate estimate.

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How to use the 1 rep max calculator

Pick your lift: deadlift, back squat, front squat, bench press, strict press or strict pull-up.
Choose lb or kg and enter the weight you lifted and how many reps you got (1 to 10).
For the strict pull-up, enter your bodyweight and the load you added. Use 0 for bodyweight-only reps and a negative number for assisted reps (for example −20 on an assisted pull-up machine).
Read your estimate. You get a blended 1RM, the range across all seven formulas, a 50–100% percentage chart and every formula's result.

Tips for an accurate estimate

Use a hard set. The formulas assume you went to failure or very close to it. A set with 3 reps left in the tank will underestimate your max.
Fewer reps is better. Studies agree that estimates are most accurate under 10 reps, and best from sets of about 2–5. That's why the calculator stops at 10.
Use strict, full-range reps. Count only reps that meet the standard you'd use for a true max.

The seven 1RM formulas

Each formula predicts your 1-rep max from the weight lifted (w) and the reps completed (r). They were built from different groups of lifters, so they agree closely at low reps and spread apart as reps go up.

Formula	Equation	225 lb × 5 reps
Epley	w × (1 + r/30)	263 lb
Brzycki	w × 36 / (37 − r)	253 lb
Lander	100w / (101.3 − 2.67123r)	256 lb
Lombardi	w × r^0.10	264 lb
Mayhew	100w / (52.2 + 41.9e^−0.055r)	268 lb
O'Conner	w × (1 + 0.025r)	253 lb
Wathan	100w / (48.8 + 53.8e^−0.075r)	262 lb

The same set of 225 × 5 gives anywhere from 253 to 268 lb, a 6% spread. That's why we don't rely on a single formula. A single (1 rep) is treated as your 1RM for that weight.

Which formulas we blend for each lift, and why

Your estimate is the average of the formulas that tested best for that lift in published studies. The full range across all seven is shown so you can see how much they disagree.

Lift	Blend	Why
Deadlift	Epley, Lombardi, Mayhew, Wathan	In LeSuer's study of the squat, bench and deadlift, every formula underestimated the deadlift by 9–14%. We blend the four that predict highest, which keeps the error smallest.
Back Squat	Epley, Brzycki, Lombardi, Wathan	Wathan was the only formula accurate for the squat in LeSuer's study. Lombardi was most accurate for men's squats and Brzycki had the least bias for women's in a later study. Epley tracks closely with Wathan.
Front Squat	Same as back squat	No studies test 1RM formulas on the front squat, so it follows the back squat.
Bench Press	Epley, Brzycki, Lander, Mayhew, Wathan	Mayhew and Wathan were accurate for the bench in LeSuer's study, and Epley came within about 1%. Brzycki and Lander were accurate from 2–10 reps in a study of 103 women and in other bench studies.
Strict Press	All seven	Research on the overhead press is thin, so we average every formula.
Strict Pull-Up	All seven	No formula has been validated for the pull-up, so we average every formula on your total load.

How the strict pull-up is calculated

In a pull-up you lift your whole body, so the load is your bodyweight plus anything you add. Pull-up research uses body mass plus added load as the load, so the calculator does the same:

Total load = bodyweight + added load

Added-load 1RM = total 1RM − bodyweight

Example: a 180 lb athlete who does 8 strict pull-ups with 25 lb has a total load of 205 lb. The formulas estimate a total 1RM of about 256 lb, so their 1RM is about +76 lb of added weight. If the estimate comes out below bodyweight, the calculator shows it as assistance, which means a true single bodyweight pull-up is the next goal.

How to use the percentage chart

Most strength programs prescribe loads as a percentage of 1RM, such as 5 sets of 3 at 85%. The chart lists 50–100% of your estimated max in 5% steps, rounded to the nearest 5 lb or 2.5 kg so it matches the plates you'll load. For the pull-up, percentages are of your total 1RM, then shown as the load to add or the assistance to use.

Limits of 1RM formulas

They estimate; they don't replace a true max test. Expect an error of a few percent from low-rep sets and more from 7–10 reps.
Endurance varies by person. Athletes with lots of conditioning often get more reps at a given percentage, which makes formulas overestimate their max.
Track changes with the same lift, rep range and formula each time. The trend is more reliable than any single number.

Want your strength work programmed for you? ZOAR Fitness coaches write percentage-based strength cycles for CrossFit athletes, built around your maxes and your schedule.

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Frequently asked questions

What is the most accurate 1 rep max formula?

No single formula wins for every lift. In head-to-head studies, Wathan and Mayhew were most accurate for the bench, Wathan for the squat, and every formula underestimated the deadlift. That's why this calculator blends the best formulas for each lift.

How many reps should I use to estimate my 1RM?

A set of 2–5 reps taken close to failure gives the best estimate. Accuracy drops above 10 reps.

How do I calculate my weighted pull-up 1RM?

Add your bodyweight to the load you used, run the 1RM formula on that total, then subtract your bodyweight. The result is how much weight you could add for a single.

Why is my deadlift estimate lower than my real max?

Deadlifts are often underestimated by formulas because lifters can grind out a heavier single than their rep sets suggest. In research, every formula came in 9–14% low on the deadlift.

Should I test my 1RM or estimate it?

Estimates are safer and good enough for setting training percentages. Test a true max when it matters, like at the end of a strength cycle or before a competition.

Sources

LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. Journal of Strength and Conditioning Research, 1997. Summaries: StrengthMath, Streatfield
Mayhew JL, et al. Accuracy of prediction equations for determining one repetition maximum bench press in women before and after resistance training. Journal of Strength and Conditioning Research, 2008. Link
Prediction equations for 1RM in the bench press, squat and arm curl (nine equations compared). Journal of the International Universities Strength and Conditioning Association. Link
Concordancia entre ecuaciones de predicción y el método de 1RM en cuatro ejercicios de entrenamiento resistido (squat, bench press, deadlift, military press). Educación Física y Ciencia. Link
Reynolds JM, Gordon TJ, Robergs RA. Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry. Journal of Strength and Conditioning Research, 2006.
Sánchez-Moreno M, et al. Movement velocity as indicator of relative intensity and level of effort attained during the set in pull-up exercise. International Journal of Sports Physiology and Performance, 2017. Link
A weight-dependent 1RM prediction equation optimized on 303,494 near-failure sets across 388 exercises. 2026. Link

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