Estimate Your One-Rep Max (1RM)
Use a weight and rep set you can perform with good form. The calculator estimates your maximum for a single repetition and suggests training loads by percentage.
What is a 1 repetition maximum (1RM)?
Your 1RM is the maximum amount of weight you can lift for one technically sound rep on a given exercise. It is a practical benchmark for setting intensity in strength programs, tracking progress over time, and choosing weights for sets like 3x5, 5x5, or 5x3.
Because testing a true max can be fatiguing and risky if poorly timed, many lifters use a submaximal set (for example, a weight they can lift 4 to 8 times) and estimate 1RM mathematically. That is exactly what this calculator does.
How to use this 1RM calculator
Step-by-step
- Pick an exercise (bench press, squat, deadlift, overhead press, etc.).
- Enter the heaviest weight you lifted in one set with clean form.
- Enter how many reps you completed at that weight.
- Select kg or lb so outputs stay in your preferred unit.
- Choose a formula, or use the average option for a balanced estimate.
For most people, the best prediction quality comes from sets in the 1–10 rep range. Predictions from very high reps can drift because muscular endurance and technique affect outcomes more strongly.
Why there are multiple formulas
No single equation perfectly models every lifter. Different formulas were built from different populations and testing methods. That is why this page includes six popular options:
- Epley: widely used, simple and practical for low-to-moderate reps.
- Brzycki: another common strength-coaching formula.
- Lombardi: uses a power relationship between reps and load.
- O'Conner: conservative progression with reps.
- Mayhew et al.: nonlinear model frequently used in research settings.
- Wathan: another nonlinear model for prediction.
If you are unsure, the Average mode can smooth out the bias of any single model and gives a stable starting number for programming.
How to apply your estimated 1RM in training
Once you have an estimate, you can assign working sets by percentage. Typical examples:
- 60–70%: speed work, technique practice, higher-volume phases.
- 70–80%: hypertrophy and general strength-building sets.
- 80–90%: heavy strength work with fewer reps per set.
- 90%+: near-maximal intensity, usually low volume and longer rest.
Most athletes should also use auto-regulation: if a weight feels unusually hard on a given day, reduce load and keep bar speed and technique high.
Example
Suppose you bench press 80 kg for 6 reps. Depending on the formula, your estimate might cluster around the low-to-mid 90s kg. A practical training plan could then use approximately 75–85% of that estimate for most weekly work sets, reserving heavier attempts for planned test days.
Safety and accuracy notes
Important reminders
- Predicted 1RM is an estimate, not a guarantee.
- Always prioritize proper form over load.
- Use spotters and safety pins for barbell movements when needed.
- Warm up thoroughly before heavy sets.
- If you are returning from injury, consult a qualified professional.
Keep a log of estimated 1RM values every few weeks on the same exercise and rep conditions. Trend lines are often more useful than any single day’s number.
Frequently asked questions
Is estimated 1RM good enough for programming?
Yes. For most lifters, estimated values are more than adequate for day-to-day planning, especially when paired with effort/RPE feedback.
Can beginners use this calculator?
Absolutely. Beginners should focus on repeatable technique and consistent training first. The calculator is a simple way to gauge progress without frequent maximal testing.
How often should I recalculate 1RM?
Every 2 to 6 weeks is common, depending on your phase and how quickly your lifts are improving.