One-rep max calculator
Estimate one-rep max from weight and repetitions.
Fill in the fields and the result will appear here automatically.
Estimate a one-repetition maximum from load and the whole-number repetitions completed in a set. Epley gives the primary result; Brzycki and Lander remain separate so their disagreement is visible. Their arithmetic mean is neither a confidence interval nor evidence that you can lift that load.
How it works
Formula and logic
For r=1 the primary result equals entered load w. Otherwise Epley = w(1+r/30). Adopted variants: Brzycki = 36w/(37−r); Lander = 100w/(101.3−2.67123r). The mean sums the three estimates and divides by 3. The product range 1–12 does not establish accuracy across that entire interval.
Example
100 kg × 5: Epley 116.7 kg, Brzycki 112.5 kg, Lander 113.7 kg and mean 114.3 kg. 80% of the primary estimate is 93.3 kg. At one repetition the primary result is 100 kg, while Lander remains a model estimate of about 101.4 kg.
Fields and units
- Weight — kg
- Repetitions — unitless
How to use
- — Enter the total working load in kilograms, greater than zero.
- — Enter 1–12 whole repetitions; fractional and higher counts are rejected.
- — Interpretation depends on proximity to fatigue and consistent technique.
- — Compare the models; percentage rows are fractions of the primary estimate only.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- LeSuer et al., 1997: 1RM model comparison and rounded coefficient variants in Table 1 Reynolds et al., 2006: repetition ranges and prediction error in bench and leg presses
- Limitation
- Model-based strength estimate without a universal accuracy guarantee. It does not establish readiness for a maximal attempt or replace assessment of technique and training conditions.
FAQ
How many repetitions does this 1RM tool accept?
1–12 whole repetitions, with a warning above 10. High-repetition sets weaken the link to maximal strength; another model is never silently replaced by Epley.
Can I use this for deadlifts and other exercises?
The arithmetic applies, but studies of particular exercises and groups do not establish the same error for every movement, machine and person.
Should I attempt the estimated maximum immediately?
The result is not clearance for a maximal lift and does not remove injury risk. It is only a reference within a separately planned training session.
Why do the three estimates and their mean differ?
Each model represents repetitions differently. The mean merely combines their numbers; it does not automatically improve accuracy.
What do the 50–90% rows prescribe?
They are arithmetic fractions of Epley’s estimate, not a programme of sets, repetitions, recovery or safe training loads.