Free One-Rep Max Calculator
Estimate your one-rep max from any submaximal lift using five validated formulas. Includes a full percentage training table for programme design. Free tool for personal trainers and strength coaches.
1. Weight Unit
2. Your Lift
Enter a weight you lifted for 1-30 reps at near-maximal effort. Most accurate at 1-10 reps.
How personal trainers use 1RM calculations in programme design
Percentage-based training is one of the most effective methods for structuring resistance programmes because it anchors load to the client's current capacity. Once you have an estimated 1RM, you can set precise intensity targets for every session rather than relying on subjective effort ratings alone.
For hypertrophy-focused clients, working at 65-80% of 1RM for 8-12 repetitions gives the best stimulus for muscle growth based on current evidence. Strength development is best achieved at 80-90% for 3-6 reps. Power work is typically programmed at 30-70% with an emphasis on bar speed and rate of force development.
Repeat the submaximal test every four to six weeks to update the 1RM estimate. Select a weight where the client completes 3-6 reps to failure or close to it. This gives the most accurate prediction across the formulas and keeps the testing process safe for clients who are not ready for true maximal lifting.
Training percentage reference guide
- 90-100% of 1RM: Maximal strength, 1-3 reps. Suitable for competitive lifters and advanced trainees only.
- 80-90% of 1RM: Strength development, 3-5 reps. Core of most strength-focused periodisation.
- 70-80% of 1RM: Strength-hypertrophy crossover, 5-8 reps. Effective for most intermediate clients.
- 60-70% of 1RM: Hypertrophy emphasis, 8-12 reps. The standard range for muscle building programmes.
- Below 60% of 1RM: Endurance, technique work, and warm-up sets.
Frequently asked questions
What is a one-rep max (1RM)?
A one-rep max (1RM) is the maximum weight you can lift for a single repetition of a given exercise with correct technique. It is the standard measure of maximal strength in resistance training and is used by personal trainers and strength coaches to set training loads, track progress, and programme periodisation cycles. The 1RM is specific to each exercise and changes as fitness improves.
How accurate are 1RM calculator formulas?
Submaximal prediction formulas are most accurate when used with lifts of 1-5 reps. Accuracy decreases as rep count increases, particularly above 10 reps. Research shows that formulas like Epley and Brzycki tend to overestimate 1RM when more than 10 reps are used. For best results, use a weight you can lift for 3-6 reps at close to maximum effort. Averaging results across multiple formulas, as this calculator does, reduces the error compared to any single formula.
What is the Epley formula?
The Epley formula is one of the most widely used 1RM prediction equations: 1RM = weight x (1 + reps/30). It was proposed by Boyd Epley in 1985 and is considered reliable for lifts of up to around 10 repetitions. The formula is simple to calculate and is embedded in many gym management and programming apps.
What is the Brzycki formula?
The Brzycki formula calculates 1RM as: weight x (36 / (37 - reps)). It is particularly accurate for low-rep efforts of 1-10 reps. The formula was developed by Matt Brzycki and is a staple in strength and conditioning programming. It gives slightly more conservative estimates than Epley at higher rep ranges.
How do personal trainers use 1RM calculations?
Personal trainers use 1RM estimates to set percentage-based training loads for clients. For example, a client training for hypertrophy might work at 65-75% of their estimated 1RM for sets of 8-12 reps, while a client training for maximal strength might use 85-95% for sets of 1-3 reps. Repeating the test every 4-8 weeks tracks strength progress and allows the trainer to update loads across the programme.
Is it safe to test a true one-rep max?
Testing a true 1RM carries injury risk, particularly for untrained individuals and for exercises like squats, deadlifts, and overhead press. The submaximal prediction approach used in this calculator is safer and appropriate for most clients. When a true 1RM test is warranted, it should be performed with adequate warm-up, a spotter, and appropriate technique, and should not be attempted by beginners or individuals with injury history without medical clearance.