One Rep Max Calculator

What is One Rep Max (1RM)?

One Rep Max (1RM) is the maximum amount of weight you can lift for one repetition of a given exercise with proper form. It's a crucial metric for strength training as it helps determine appropriate training loads for different goals.

Rather than testing your 1RM directly (which can be risky and fatiguing), you can estimate it using mathematical formulas based on a weight you can lift for multiple repetitions. This calculator uses seven scientifically validated formulas to give you accurate 1RM estimates.

1RM Calculation Formulas

Epley (Most Popular)

The Epley formula (1985) is one of the most widely used and accurate formulas for estimating 1RM. It's particularly reliable for repetitions in the 1-10 range and is commonly used by strength coaches and athletes.

1RM = Weight × (1 + 0.0333 × Repetitions)

Brzycki

The Brzycki formula (1993) is another popular and accurate formula, especially for lower rep ranges (1-10 reps). It's commonly used in strength training programs and research.

1RM = Weight × 36 / (37 - Repetitions)

Lander

The Lander formula (1985) provides accurate estimates across a wide range of repetitions. It's known for being conservative and reliable.

1RM = (100 × Weight) / (101.3 - 2.67123 × Repetitions)

Training Zones & Rep Ranges

How to Use This Calculator

1. Perform an exercise (like bench press, squat, or deadlift) with a weight you can lift for multiple reps (ideally 3-10 reps)
2. Enter the weight you lifted and the number of repetitions completed
3. Choose a formula or use "Average of All Formulas" for the most balanced estimate
4. Review your estimated 1RM and training percentages
5. Use the training percentages table to plan your workouts based on your goals

Tips for Best Results

• Use a weight that challenges you but allows you to maintain proper form throughout all repetitions
• The most accurate estimates come from sets of 3-10 reps. Higher reps (15-20) are less accurate
• Always warm up properly before attempting heavy lifts
• For the most accurate results, test with reps between 3-8
• Different formulas may give slightly different results - using the average can provide a balanced estimate
• Re-test your 1RM estimate every 4-6 weeks as you get stronger
• Use training percentages to create periodized programs (varying intensity throughout your training cycle)
• For max strength (95-100%), rest 3-5 minutes between sets
• For hypertrophy (70-85%), rest 60-90 seconds between sets
• For endurance (60-70%), rest 30-60 seconds between sets

Important Safety Notes

• These formulas provide estimates - individual results may vary based on training experience and muscle fiber composition
• Never attempt a true 1RM test without proper warm-up and spotters
• Beginners should focus on learning proper form before testing or estimating 1RM
• The accuracy decreases significantly for reps above 15
• These calculations are most accurate for compound movements (squat, bench press, deadlift, overhead press)
• Always use proper form and never sacrifice technique for heavier weights
• If you're new to strength training, work with a qualified coach or trainer
• Listen to your body - if something doesn't feel right, stop immediately
• Progressive overload should be gradual - don't increase weights too quickly
• Adequate rest and nutrition are essential for strength gains and injury prevention