Wathan Formula: 1RM Calculator and Complete Guide

History and origin

Daniel Wathan published his 1RM prediction equation in 1994 as a chapter in the NSCA's "Essentials of Strength Training and Conditioning" — the foundational textbook for the CSCS certification. Wathan's formula refines the exponential decay structure of Mayhew's earlier model with coefficients calibrated specifically on competitive powerlifters and Olympic weightlifters: 1RM = 100 × weight / (48.8 + 53.8 × e^(−0.075 × reps)). Because it was developed on athletes whose strength curves are shaped by years of low-rep, high-intensity training, Wathan is particularly accurate for heavy loads (1-6 reps) and competition-style testing.

How to use the Wathan formula (step by step)

1. Perform a heavy submaximal set. Perform a clean set of 2-10 reps to near-failure (RPE 8-9) on the lift you want to test. Record the weight and the rep count.
2. Apply the Wathan equation. 1RM = 100 × weight / (48.8 + 53.8 × e^(−0.075 × reps))
3. Read the estimated 1RM. The output is your estimated 1RM. For programming, multiply by 0.9 to derive your Training Max — this absorbs daily strength variability and reduces overshoot risk.
4. Cross-check against other formulas. Run the same numbers through every other formula and compare. The main calculator does this automatically using a trimmed mean.

How Wathan compares to the other six formulas

The same submaximal set — 225 lb × 5 reps — produces different 1RM estimates depending on which formula you use. Here are all seven, side by side:

See the full formula comparison page for accuracy data and decision-making guidance.

Validation research

The Wathan formula has been evaluated in multiple peer-reviewed studies of 1RM prediction accuracy. Selected findings:

Wathan in the NSCA Essentials textbook

Daniel Wathan published his 1RM prediction equation as a chapter contribution to the first edition of the NSCA's Essentials of Strength Training and Conditioning in 1994. The book — edited by Thomas R. Baechle — is the foundational reference for the Certified Strength and Conditioning Specialist (CSCS) credential. Every CSCS-certified coach in the world has formally studied Wathan's formula as part of the certification curriculum, which is one reason it remains widely recognized in collegiate and professional strength coaching despite being newer than Epley or Brzycki.

Wathan's chapter, “Load Assignment,” addresses the practical problem coaches face daily: how do you prescribe a percentage-based program when you don't want to subject athletes to true 1RM tests? His formula and the associated load-assignment tables (1RM × percentage = working weight) became the NSCA standard reference for this calculation. Subsequent editions of Essentials retain the formula across all major revisions through 2024.

Calibration on competitive lifters

The key methodological choice that distinguishes Wathan from Mayhew: Wathan calibrated his exponential decay coefficients (48.8, 53.8, −0.075) on competitive powerlifters and Olympic weightlifters rather than general college students. Two consequences fall out of this:

• Steeper decay constant (−0.075 vs Mayhew's −0.055). Trained athletes have a shallower rep-to-1RM relationship at low reps (their 5RM is closer to their 1RM than the average lifter's); the steeper decay captures this.
• More accurate for low-rep heavy training. In the 1-6 rep range, Wathan typically beats Mayhew by 1-3% on competitive lifters. For general fitness populations doing high-rep work, the relationship inverts.

This is why a competitive powerlifter peaking with heavy doubles and triples should prefer Wathan; a hypertrophy-focused gym lifter testing with sets of 8-12 should prefer Mayhew. Neither is universally “better” — they were calibrated on different populations.

Wathan vs Brzycki at low reps

For trained athletes in the 1-6 rep range, Wathan and Brzycki are the two most accurate single formulas. In head-to-head comparisons:

The two formulas agree to within 1-3% across the standard testing rep range — meaningful for elite tracking but indistinguishable for general programming. For competitive powerlifters who train predominantly in the 1-6 rep range, using either formula is fine; using both as a sanity check is better.

Wathan in collegiate strength coaching

Because the NSCA Essentials textbook teaches Wathan as the canonical reference, collegiate strength coaches often default to it when programming for athletes. Practical applications include:

• Off-season testing weeks. Athletes perform a 3RM or 5RM test (lower CNS cost than a true 1RM); Wathan converts to 1RM for the percentage-based prescription that follows.
• In-season load tracking. Athletes typically can't afford a true 1RM test mid-season; Wathan-derived 1RMs from their working sets serve as the moving programming target.
• Returning from injury. A lifter returning to heavy training shouldn't test true 1RM immediately. Wathan + a heavy 5 produces a conservative starting point.
• Pairs naturally with 5/3/1 and other percentage-based templates: a Wathan-estimated 1RM × 90% gives the Training Max needed.

References

1. Original publication: Wathan, D. (1994). Load assignment. In: Essentials of Strength Training and Conditioning (T.R. Baechle, ed.). Champaign, IL: Human Kinetics, pp. 435-446.
2. LeSuer et al. (1997): LeSuer, D.A., McCormick, J.H., Mayhew, J.L., Wasserstein, R.L., & Arnold, M.D. (1997). The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. Journal of Strength and Conditioning Research, 11(4), 211-213.
3. Reynolds et al. (2006): Reynolds, J.M., Gordon, T.J., & Robergs, R.A. (2006). Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry. Journal of Strength and Conditioning Research, 20(3), 584-592.
4. Wood et al. (2002): Wood, T.M., Maddalozzo, G.F., & Harter, R.A. (2002). Accuracy of seven equations for predicting 1-RM performance of apparently healthy, sedentary older adults. Measurement in Physical Education and Exercise Science, 6(2), 67-94.
5. Wikipedia: One-repetition maximum — general reference for 1RM prediction equations.
6. Essentials of Strength Training and Conditioning (NSCA, Human Kinetics) — NSCA CSCS textbook chapter on load assignment.