Strength estimate
Estimate a one-rep max from a completed set and turn it into useful warm-up, strength, and volume targets.
Enter a completed set and choose a formula.
Method
Wathan, Epley, Brzycki, Lombardi, or O'Conner 1RM equations
Practical context
Estimate your one-rep max from a completed set with Wathan, Epley, Brzycki, Lombardi, or O'Conner. Use the result to build training percentages without testing a true maximum every time your strength changes.
A one-rep max, or 1RM, is the heaviest load you can lift once with the required technique for a specific exercise. An estimate converts a submaximal set into a projected maximum, reducing the need for frequent true-max attempts.
The estimate belongs to that exercise variation and technique. A touch-and-go bench press, paused bench press, high-bar squat, and low-bar squat should not be treated as interchangeable tests.
Researchers and coaches have proposed multiple equations because the relationship between repetitions and maximum strength varies. GymDaze keeps the legacy five-formula selection so you can use the same method consistently.
| Formula | Equation using weight w and reps r |
|---|---|
| Wathan | 100w / (48.8 + 53.8e^(-0.075r)) |
| Epley | w x (1 + r / 30) |
| Brzycki | 36w / (37 - r) |
| Lombardi | w x r^0.10 |
| O'Conner | w x (1 + 0.025r) |
Use a challenging set completed with normal technique and a known repetition count. Lower-repetition sets generally resemble maximum-strength performance more closely. Very high repetitions make conditioning, pain tolerance, pacing, and local muscular endurance more influential.
Do not intentionally grind an unsafe set merely to improve the estimate. A repeatable set that leaves little uncertainty is more valuable than a breakdown in technique.
The percentage table translates the estimate into working loads. Heavy singles may use a high percentage without becoming true max attempts, while moderate percentages can organize strength and volume work.
Round to plates you can load and adjust for the exercise, session goal, and fatigue. Percentage prescriptions are starting points. Autoregulation, repetitions in reserve, and performance on the day can justify a change.
Use the same formula and comparable set conditions when tracking progress. A different exercise order, pause, range of motion, repetition speed, or fatigue level can change the estimate.
A short-term increase can reflect better skill or a better test set rather than new muscle. That is still useful performance, but interpret the number with the training log.
Questions people ask
