RM
calculator
Estimate your max (1RM) without risking a real test: enter the weight you moved and the reps you got, and the Brzycki formula does the rest.
Your 1RM from one set
Any set taken close to failure works (1 to 10 reps).
Bodyweight exercises
Pull-ups, dips and similar: the added weight for your 1RM and for a target percentage.
How to get a 1RM you can trust
The formula is only as good as the set you feed it. This is the short protocol that makes the number worth something.
- 1Warm up on a ramp8-10 easy reps, then 5 at 50%, 3 at 70% and 1-2 at 80% of what you think your max is.
- 2Pick 3-5 repsThe load should leave you 3 to 5 clean reps. The fewer the reps, the more accurate the estimate.
- 3Rest 3-5 minutesStacking attempts without rest measures your fatigue instead of your strength.
- 4Stop with 0-1 reps in reserveAnd with technique intact: an ugly rep does not count as a rep.
- 5Record it at 100%Save the result as your max for the exercise. From then on every plan percentage turns into kilos by itself.
- 3RM
- ≈ 94% of 1RM
- 5RM
- ≈ 89% of 1RM
- 8RM
- ≈ 81% of 1RM
- Long sets: past 6-8 reps it overstates your max and you end up training heavier than intended.
- Sets far from failure: with 4 reps still in the tank the number is worthless.
- Finger strength on a dynamometer: nothing is estimated there, a real maximal pull is measured.
We use the Brzycki formula, the standard for estimating a 1RM without testing it: 1RM = weight ÷ (1.0278 − 0.0278 × reps). It gets more accurate the fewer reps the set has (ideally 6 or fewer) and the closer it is to failure.
Frequently asked questions
What is a 1RM?
The most weight you can move exactly once in an exercise with proper technique. It is the reference strength training is programmed on: plans prescribe percentages of that max.
How accurate is the estimate?
It is a reliable estimate for programming, not a lab test. With sets of 6 reps or fewer close to failure, the typical error is around 2-5%. More than enough to compute your working percentages.
What about bodyweight exercises?
Use the second calculator: it adds your body weight to the external load, estimates the total max and gives you back only the added weight, which is what you can adjust in the gym.
How often should I recalculate it?
Whenever your performance clearly changes. In Fishlimpia you do not have to: the app re-estimates your RM per exercise and per variation after every logged session.
Stop doing the math by hand
Fishlimpia stores your RM per exercise and variation and converts every percentage in the plan to kilos, session after session.
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