1RM Calculator (Calculadora de Fuerza Máxima)
Use this one rep max calculator to estimate your maximum strength from a weight you can lift for multiple reps.
How to calculate 1RM correctly
If you searched for 1rm calcular, you likely want a fast and reliable way to estimate your maximum strength without doing a risky all-out single. A 1RM (one-rep max) is the heaviest load you can lift one time with proper form in a given exercise, such as the squat, bench press, or deadlift.
Testing a true max can be useful, but it also creates fatigue and injury risk. That is why many coaches use a calculadora 1RM: you perform a safe set for multiple reps, then estimate your max using a proven formula.
Why lifters use a one rep max calculator
- Safer planning: You can train based on percentages without maxing out weekly.
- Progress tracking: Estimated 1RM helps you compare strength over time.
- Program design: Most strength programs prescribe loads like 70%, 80%, or 90% of 1RM.
- Fatigue management: You avoid unnecessary high-stress testing sessions.
Popular 1RM formulas and when to use them
Epley formula
Simple and common in powerlifting and general strength training. Works well in moderate rep ranges (about 1 to 10 reps).
Brzycki formula
Often slightly more conservative than Epley, especially as reps increase. Most reliable under 10 to 12 reps.
Lombardi, O'Conner, Mayhew, and Wathan
These formulas model fatigue differently. There is no perfect equation for every lifter, so using an average is a smart approach for most people.
Best practices for accurate estimates
- Use a set performed with strict, consistent form.
- Stay in a practical rep range (ideally 2 to 10 reps).
- Avoid using sets taken when you are severely fatigued.
- Estimate separately for each lift (bench, squat, deadlift, overhead press).
- Recalculate every 3 to 6 weeks as your strength changes.
How to use your estimated 1RM in training
After you calculate your one rep max, use it to assign working weights by percentage:
| Goal | % of 1RM | Typical Rep Range |
|---|---|---|
| Technique / Speed | 55%–70% | 3–6 reps |
| Hypertrophy | 65%–80% | 6–12 reps |
| Strength | 80%–90% | 3–6 reps |
| Peaking / Heavy Singles | 90%–97% | 1–2 reps |
Example: estimating your max
Suppose you bench press 85 kg for 6 reps. Depending on the formula, your estimated max might be around 99 to 103 kg. That gives you a practical training max around 90 to 93 kg (using a 90% training max model), which can be used to plan your next training block.
Limitations to remember
A calculator gives an estimate, not an absolute truth. Sleep, stress, nutrition, technique quality, and exercise variation all affect true daily strength. Use estimated 1RM as a guide, then adjust based on bar speed, RPE, and recovery.
Quick safety reminder
Never force a maximal attempt when form breaks down. If you are new to lifting, get coaching for setup, bracing, and spotting before chasing PRs.