🏋️One Rep Max Calculator

A one rep max calculator estimates the maximum weight you could lift for a single complete repetition on any given exercise, using a lighter submaximal set as the input. The 1RM is the foundational number in evidence-based strength programming. Nearly every major training methodology, from powerlifting periodization to bodybuilding hypertrophy blocks, prescribes training loads as a percentage of 1RM. Knowing your 1RM lets you train at the exact intensity needed to produce the adaptation you are after, without guessing.

How to Calculate Your One Rep Max for Bench Press, Squat, and Deadlift

To use a 1RM calculator, perform a working set on the exercise you want to estimate. Choose a weight that allows you to complete 3 to 5 repetitions with proper form while leaving 1 to 2 reps in reserve. Enter the weight and rep count into the calculator. The formulas extrapolate what your maximum single-rep capability would be based on the load-repetition relationship established across large populations of trained lifters.

The most reliable input data comes from heavy sets of 1 to 6 reps. As rep count increases above 8, the estimate becomes less accurate because muscular endurance, cardiovascular fatigue, and mental fortitude play a growing role in determining how many reps you complete, independent of absolute strength. For programming purposes, a 3RM to 5RM test gives you the best balance of accuracy, safety, and manageability.

The compound barbell movements, bench press, squat, deadlift, and overhead press, are where 1RM estimation is most useful and most validated. The formulas perform less reliably for isolation exercises like curls and lateral raises, where fatigue accumulates differently and form breakdown is more variable.

Epley vs Brzycki One Rep Max Formula: Which to Use

Five formulas are commonly used in strength training research and coaching. This calculator averages all five to produce a more stable estimate than any individual formula provides.

Epley Formula

Developed by Boyd Epley at the University of Nebraska in 1985. The formula is: 1RM equals weight multiplied by the quantity 1 plus reps divided by 30. It is the most widely cited formula in both academic literature and coaching practice. Accuracy is highest in the 1 to 10 rep range and it tends to slightly overestimate at higher rep counts. Most commercial strength training software defaults to this formula.

Brzycki Formula

Developed by Matt Brzycki of Princeton University in 1993. The formula is: 1RM equals weight multiplied by 36 divided by the quantity 37 minus reps. It produces very similar results to the Epley formula at low rep counts and diverges at higher reps. Many powerlifting coaches prefer the Brzycki formula for its accuracy in the 3 to 6 rep range used during competition prep cycles. For sets of 10 or more reps, Brzycki becomes less reliable.

Lander, Lombardi, and Mayhew Formulas

The Lander formula uses a linear denominator and produces slightly more conservative estimates. The Lombardi formula applies a power function rather than a linear relationship, handling higher rep inputs differently from the other four. The Mayhew formula uses an exponential model and is frequently cited as performing best in the 6 to 15 rep range when estimating from moderate-rep working sets. Averaging all five provides better coverage across the full range of possible inputs than committing to any single formula.

Training Percentages Based on 1RM

Once you have your estimated 1RM, use these percentage ranges to select the right training load for each session goal:

• 50 to 60 percent of 1RM: Warm-up sets, technique practice, and very high-rep endurance work above 15 repetitions. Builds movement quality and work capacity.
• 60 to 70 percent: Muscular endurance and hypertrophy training in the 12 to 15 rep range. Useful in high-volume accumulation phases.
• 70 to 80 percent: The primary hypertrophy zone at 8 to 12 reps. Most bodybuilding and general fitness programs spend the majority of training volume here.
• 80 to 85 percent: Strength-hypertrophy crossover at 5 to 8 reps. Builds both size and strength and is common in intermediate powerlifting and strength programs.
• 85 to 90 percent: Maximal strength development at 3 to 5 reps. Requires good technique and adequate recovery. Used in strength peaking phases.
• 90 to 95 percent: Near-maximal efforts of 1 to 3 reps. Develops maximal strength expression and neural recruitment. Reserved for experienced lifters.
• 95 to 100 percent: True maximal effort. Used only for competition attempts or formal testing, not routine training.

Progressive Overload and 1RM Updates

Maximal strength improves with consistent progressive overload, systematically increasing the training stimulus over time. Because your 1RM changes as you get stronger, programming based on outdated 1RM values leads to training that is either too light to produce strength gains or too heavy to recover from properly. Re-estimating your 1RM every four to eight weeks keeps your training percentages calibrated to your current fitness level. Performing a fresh 3RM to 5RM test at the start of each training block and entering the results into this calculator takes less than a single set and provides updated numbers for the entire next phase of training.