One Rep Max (1RM) Calculator
Estimate your one-repetition maximum (1RM) for any exercise based on the weight you can lift for multiple repetitions.
What is One Rep Max (1RM)?
One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise with proper form. It's a standard measure of strength and is often used to:
- Track strength progress over time
- Compare relative strength between individuals
- Determine appropriate training loads (as percentages of 1RM)
- Design periodized training programs
- Set strength goals
1RM Estimation Formulas
While the most accurate way to determine your 1RM is to actually perform a single maximum effort lift, this can be risky, especially for beginners. Several formulas have been developed to estimate 1RM based on submaximal loads:
Brzycki Formula
1RM = Weight × (36 / (37 - Reps))
Most accurate for repetitions under 10.
Epley Formula
1RM = Weight × (1 + (0.0333 × Reps))
Works well for a wide range of repetitions.
Lander Formula
1RM = (100 × Weight) / (101.3 - 2.67123 × Reps)
Another widely used formula with good accuracy.
Lombardi Formula
1RM = Weight × Reps^0.10
Simple formula that works reasonably well for moderate rep ranges.
Training with Percentages of 1RM
Once you know your 1RM, you can design your training program using percentages of this maximum. Different percentage ranges target different training adaptations:
| Percentage of 1RM | Rep Range | Training Effect |
|---|---|---|
| 95-100% | 1-2 | Maximum strength, neural adaptation |
| 85-95% | 3-5 | Strength, some hypertrophy |
| 75-85% | 6-8 | Strength and hypertrophy |
| 65-75% | 8-12 | Hypertrophy, some strength |
| Below 65% | 12+ | Muscular endurance, some hypertrophy |
Limitations of 1RM Estimation
While 1RM estimation formulas are useful, they have some limitations:
- Most accurate when using repetitions under 10 (ideally 1-5 reps)
- Accuracy varies between different exercises (better for compound movements)
- Individual factors like training experience and muscle fiber composition affect accuracy
- Doesn't account for technique breakdown at maximal loads
- May overestimate 1RM for beginners and underestimate for advanced lifters
Safety Considerations
When testing or training near your 1RM:
- Always use proper form and technique
- Have spotters or safety equipment when attempting heavy lifts
- Warm up thoroughly before heavy lifting
- Progress gradually to heavier weights
- Listen to your body and avoid lifting through pain
- Consider working with a qualified strength coach for maximal testing
Tracking Progress
To effectively track strength progress:
- Re-test your estimated 1RM every 4-8 weeks
- Use the same formula consistently for comparison
- Test under similar conditions (time of day, rest, nutrition)
- Track both absolute strength (total weight) and relative strength (weight relative to body weight)
- Consider using a strength training app or journal to record progress