One Rep Max Calculator
Estimate your maximum one-repetition lift (1RM) from any submaximal set using 7 validated strength formulas, complete with percentage training charts and rep max tables.
Estimated 1RM by Formula
All 7 peer-reviewed equations| Formula | Est. 1RM (lb) | Converted (kg) | Diff vs. Avg |
|---|
Enter your weight lifted and repetitions performed on the left, then click Calculate 1RM.
Percentage Training Table
Based on Epley 1RMApproximate training loads for strength, hypertrophy, and warm-ups.
| % of 1RM | Weight (lb) | Weight (kg) | Est. Reps | Zone |
|---|
Repetition Maximums (1RM–15RM)
Based on Epley FormulaEstimated maximum weight you can lift for target repetitions.
| Target Reps | % of 1RM | Est. Weight (lb) | Est. Weight (kg) |
|---|
What Is One Rep Max (1RM)?
One Rep Max (1RM) is the maximum amount of weight you can lift for a single, complete repetition of an exercise with proper form. In strength training and powerlifting, your 1RM serves as the primary benchmark for measuring absolute muscular strength and prescribing percentage-based training weights.
What Is a 1RM Calculator?
A 1RM Calculator estimates your maximum lifting capacity from a lighter, submaximal set (such as lifting a weight for 3 to 10 repetitions). This eliminates the safety risks and high central nervous system fatigue associated with testing a true, maximal 1-rep lift in the gym.
How Does the One Rep Max Calculator Work?
There is a predictable mathematical relationship between the weight on the bar and how many reps you can complete before muscular failure. The calculator combines your input weight, repetition count, and 7 peer-reviewed sports-science formulas (Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner, and Wathan) to calculate accurate strength predictions.
1RM Formulas Explained
1. Epley Formula
1RM = W × (1 + R / 30)
The most widely used linear equation in strength coaching.
2. Brzycki Formula
1RM = W × 36 / (37 − R)
A conservative hyperbolic equation popular among powerlifters.
3. Lander Formula
1RM = (100 × W) / (101.3 − 2.67123 × R)
Linear percentage-decay model for submaximal sets.
4. Lombardi Formula
1RM = W × R0.10
Logarithmic power-law model preventing high-rep inflation.
5. Mayhew et al. Formula
1RM = (100 × W) / (52.2 + 41.9 × e−0.055 × R)
Exponential decay curve derived from athletic testing.
6. O'Conner et al. Formula
1RM = W × (1 + R / 40)
Conservative linear formula adding 2.5% per repetition.
7. Wathan Formula
1RM = (100 × W) / (48.8 + 53.8 × e−0.075 × R)
Frequently cited by the NSCA for mixed athletic populations.
Frequently Asked Questions (FAQ)
What is a one rep max?
A one rep max (1RM) is the heaviest weight you can successfully lift for a single repetition of an exercise using proper form and full range of motion.
How accurate is a 1RM calculator?
When you input a set of 2 to 10 strict repetitions taken close to muscular failure, a 1RM calculator is typically accurate within 2% to 5% of your actual one-rep max.
Can I calculate bench press, squat, and deadlift 1RM?
Yes. The formulas apply to all major compound lifts. For deadlifts, ensure you perform dead-stop reps rather than bouncing plates off the floor.
What is 80% of my 1RM?
80% of your 1RM is your max multiplied by 0.80. Most lifters can perform approximately 7 to 8 repetitions at this intensity, making it ideal for strength and hypertrophy training.