📐 1RM Calculator
Enter the weight lifted and the number of repetitions – we will calculate your theoretical one-repetition maximum (1RM).
🧪 What Is 1RM?
1RM (One Repetition Maximum) – this is the maximum weight you can lift once with proper technique. It is the gold standard of strength in the sports world.
Knowing your 1RM allows you to accurately plan training loads – each percentage zone of 1RM develops different physical qualities:
- 85–100% 1RM – developing maximal strength (1–5 reps)
- 70–85% 1RM – muscle hypertrophy / mass gain (6–12 reps)
- 50–70% 1RM – strength endurance (12–20+ reps)
- <50% 1RM – warm-up, rehabilitation, technique refinement
⚠️ Safety Reminder
This is theoretical 1RM calculation. Never attempt a true 1RM without proper warm-up, technique mastery and partner assistance. The difference between theoretical and actual 1RM can reach 5-10%.
📚 Formula Comparison
Different formulas can give slightly different results. Here is how they work:
🏆 Epley
The most popular formula. Works well in the 1–10 rep range. 1RM = Weight × (1 + reps / 30).
📏 Brzycki
Most precise for lower rep counts (<10). 1RM = Weight × 36 / (37 – reps).
📐 Lombardi
Works better for higher weights and low rep counts. 1RM = Weight × reps0.10.
📊 O'Conner
Similar to Epley, but more conservative for high rep counts.
🔬 Wathen
Uses an exponential curve, suitable for a wider rep range.
📈 Mayhew
Similar to Wathen with slightly different constants, accurate up to 10 reps.
💡 1RM Training Tips
🔄 Periodization
Do not chase personal records every workout. Use periodization: 4 weeks of hypertrophy, 2 weeks of strength, 1 week of recovery.
🔥 Warm-Up
Before testing 1RM: 10 reps at 50%, 5 reps at 70%, 3 reps at 80%, 1 rep at 90%, then the attempt. Rest 3-5 min. between sets.
🍽️ Nutrition
On strength days, eat enough carbohydrates. Protein intake: 1.6–2.2 g/kg body weight. Creatine can increase 1RM by 5–15%.
🛡️ Safety
Always use safety stands for squats and bench press. Have a spotter who can help. Never use a thumbless grip.
❓ Frequently Asked Questions
Do these formulas work for all exercises?
Yes, 1RM formulas are universal and work for all major exercises – bench press, squats, deadlift, overhead press, etc. However, accuracy may vary slightly depending on the biomechanics of the exercise.
How many repetitions is it best to use for the calculation?
It is optimal to use 3–8 repetitions. With more than 10 repetitions, the formulas become less accurate because the influence of the muscular endurance factor increases. At 1–2 repetitions, the result is almost equal to the actual 1RM.
What Is the Difference Between the Formulas?
The difference between formulas usually does not exceed 3–5%. We recommend using the average – it is the most reliable indicator. The Brzycki formula is considered the most accurate in the rep range 1–10.
How Often Should 1RM Be Tested?
It is recommended to test every 8–12 weeks. Lifting maximal weights too often increases the risk of injury and can lead to overtraining. It is better to track progress using 3–5 RM and occasionally perform a true 1RM test.