Estimate your maximum single-rep lift and plan your training intensity
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Your estimated 1RM grows as you get stronger - but only if you progressively overload. SatisFIT tracks every set and shows your strength curve over time so you never plateau without knowing. Try SatisFIT free
One Rep Max (1RM) is the maximum weight you can lift for a single repetition with proper form. It's a key metric for programming training intensity and tracking strength progress over time. Most percentage-based programs prescribe weights as a percentage of your 1RM, making it essential for structured training. You can use your estimated 1RM in the Strength Level Calculator to see how your lifts compare to strength standards.
This calculator uses the average of two well-established formulas: Epley (weight x (1 + reps/30)) and Brzycki (weight x 36 / (37 - reps)). Both are most accurate for sets of 1-10 reps. For higher rep ranges, estimates become less reliable because muscular endurance becomes a larger factor than pure maximal strength.
Anyone who follows a percentage-based training program needs to know their 1RM. This calculator lets you estimate it from a submaximal set, which is safer than actually attempting a true one-rep max. It's useful for beginners planning their first structured program, intermediate lifters tracking progress, and advanced lifters who want to plan training cycles without maxing out frequently.
The most common mistake is using a set with poor form as the input. If you had to grind out the last reps with compromised technique, the estimate will be artificially high. Use a set performed with clean, controlled form for the most accurate result. Another frequent error is using high-rep sets (above 10 reps) - these rely more on endurance than strength, making the 1RM prediction less reliable. Stick to sets of 3-8 reps for the best accuracy.
For sets of 1-6 reps, calculators are typically within 5% of your actual max. Accuracy decreases with higher rep counts because endurance factors become more significant. The Brzycki and Epley formulas are among the most validated in strength science literature.
Testing a true 1RM carries higher injury risk and requires a spotter. For most people, estimating from a 3-5 rep set is safer and nearly as accurate. True 1RM testing is mainly necessary for competitive powerlifters who need to know their exact max for competition.
Every 4-8 weeks is a good cadence for retesting. Your 1RM changes as you get stronger, so outdated numbers lead to training with weights that are too light. Simply enter your latest heavy set and the calculator updates your estimate instantly.
Each formula models the relationship between reps and max strength slightly differently. Epley tends to give higher estimates at higher rep counts, while Brzycki is more conservative. This calculator averages both to give you the most balanced estimate. The difference is usually small (under 3%) for sets of 1-8 reps.