One Rep Max Calculator

Weight Lifted: Repetitions Performed: Results Unit: 1RM Estimation Formula:

Results

What is a One Rep Max (1RM)?

One Rep Max (1RM) refers to the maximum weight you can lift for a single repetition of an exercise while maintaining proper form. It is a crucial measurement for strength training, powerlifting, and bodybuilding, helping athletes and fitness enthusiasts track progress and set training goals.

Read Also : RPE Calculator

Why is 1RM important?

Estimating your 1RM allows you to:
✔ Set training intensity levels
✔ Plan progressive overload
✔ Determine ideal rep ranges for muscle growth and strength
✔ Avoid overtraining and injury by lifting appropriate weights

How to Calculate 1RM?

Since performing a true one-rep max test can be risky, fitness professionals use estimation formulas to calculate 1RM based on the weight lifted and reps performed.

Popular 1RM Formulas

Different formulas are used to estimate 1RM. Our One Rep Max Calculator supports:

Epley Formula: $\text{weight} \times (1 + \frac{\text{reps}}{30})$
Brzycki Formula: $\text{weight} \times \frac{36}{37 – \text{reps}}$
McGlothin Formula: $\frac{100 \times \text{weight}}{101.3 – 2.67123 \times \text{reps}}$
Lombardi Formula: $\text{weight} \times \text{reps}^{0.1}$
Mayhew Formula: $\frac{100 \times \text{weight}}{52.2 + (41.9 \times e^{-0.055 \times \text{reps}})}$

Each formula provides slightly different results, and our calculator allows you to select your preferred method or use an average of all formulas for a balanced estimate.

How to Use the 1RM Calculator?

Enter the weight lifted (in kg or lbs).
Enter the number of reps performed (between 1-10 reps for best accuracy).
Select the unit (kg or lbs).
Choose a 1RM estimation formula or use the average calculation.
Click “Calculate” to see your estimated One Rep Max.

How to Use 1RM for Training?

Once you know your 1RM, you can use it to determine your training loads:

Strength Training (85-100% 1RM): 1-5 reps per set
Hypertrophy (Muscle Growth) (65-85% 1RM): 6-12 reps per set
Endurance Training (50-65% 1RM): 12+ reps per set

Using these percentages helps structure an effective and safe training program tailored to your fitness goals.

Final Thoughts

A One Rep Max Calculator is an essential tool for anyone serious about strength training. It allows for precise weight selection, helping you progress efficiently while minimizing injury risks. Whether you’re a beginner or an advanced lifter, tracking your 1RM ensures you stay on top of your strength gains.