One Rep Max Calculator
Estimate your 1RM and build a full training percentage table
One Rep Max Calculator
Estimate your 1RM and build a full training percentage table
Enter Your Lift
About One Rep Max Calculator
Your One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise. It is the gold standard for measuring absolute strength in powerlifting, Olympic weightlifting, and strength training.
Testing your true 1RM carries injury risk, especially for beginners. This calculator uses 6 validated formulas — Epley, Brzycki, Lombardi, Mayhew, O'Conner, and Wathen — to predict your 1RM from a sub-maximal set (e.g. 5 reps at 80% of your max). The average of all six formulas gives a more reliable estimate than any single formula alone.
The resulting training percentage table lets you build structured programs by automatically calculating the correct weight for any intensity zone — useful for strength blocks, hypertrophy phases, and peaking cycles.
Note: These are estimates. Individual response to training, technique, fatigue, and bar speed all affect true 1RM. Always warm up properly and use a spotter when lifting heavy.
How to Use One Rep Max Calculator
- Select your unit — choose pounds (lbs) or kilograms (kg) using the toggle button.
- Enter the weight — type the weight you lifted in the "Weight Lifted" field. Use any set where you reached near-failure.
- Enter the reps — type the number of reps you completed with that weight (best accuracy between 1–10 reps; still usable up to 30).
- Read your 1RM — your estimated one rep max appears instantly as the average of 6 formulas.
- Use the percentage table — the table shows calculated weights for each intensity zone. Use these in your training program to hit specific percentages automatically.
Pro tip: For the most accurate estimate, use a set of 3–6 reps performed at a true near-failure effort. Very high rep sets (15+) tend to overestimate 1RM for strength athletes.
Frequently Asked Questions
What is a one rep max (1RM)?
A one rep max is the maximum weight you can lift for exactly one full repetition with good form. It is the most common way to measure absolute strength and is used to set training intensities across powerlifting, Olympic lifting, and general strength programs.
Which formula is most accurate?
No single formula is universally best — accuracy depends on the individual and rep range. The Epley and Brzycki formulas are the most widely cited. For lower rep ranges (1–6), Brzycki tends to be slightly more accurate. This calculator averages all six to reduce individual formula bias.
How many reps should I use for the best estimate?
Use a set of 3–6 reps at near-failure for the most reliable estimate. Sets of 1–10 reps give good results. Beyond 10 reps accuracy drops significantly, and beyond 20 reps these formulas are not reliable for most lifters.
Can I use this for any exercise?
Yes — the formulas work for any barbell, dumbbell, or machine lift: squat, bench press, deadlift, overhead press, rows, curls, and more. Just enter the weight and reps for the specific exercise you want to estimate.
What does the training percentage table mean?
Strength programs prescribe work at percentages of your 1RM. For example, "3 sets of 5 at 85%" means you should use 85% of your 1RM. The table calculates the actual weight for each percentage so you don't need to do the math manually. Higher percentages (90–100%) target max strength; lower percentages (60–75%) target hypertrophy and endurance.
Is it safe to attempt my 1RM?
Maximal testing carries a higher injury risk than sub-maximal work. Always warm up thoroughly, use a spotter or safety rack, and avoid true 1RM testing if you are a beginner or returning from injury. The estimated 1RM from this calculator lets you program by percentage without needing to test your actual max.
Why is the calculator showing different numbers than I expected?
The formulas assume you reached true near-failure on your set. If you stopped several reps short, the estimated 1RM will be lower than your actual capacity. Conversely, if your technique breaks down under fatigue, the estimate may be inflated. For best results, log a set where you gave maximum effort for the chosen rep count.