1 Rep Max Calculator
Enter one completed set to compare two common exercise-specific 1RM estimates.
Estimate 1RM from weight and reps
A one-repetition maximum, or 1RM, is the heaviest load completed for one repetition of a specific exercise. This calculator estimates it from a set you have already completed. Enter the external load shown on the bar, dumbbells, machine, or other equipment, keep the unit consistent, and use a whole-number repetition count from 1 to 10.
For example, 225 lb completed for five reps gives an Epley estimate of 262.5 lb and a Brzycki estimate of 253.1 lb. A 100 kg set for five reps gives 116.7 kg and 112.5 kg. The tool keeps those answers separate because the difference is useful evidence of formula uncertainty.
Epley and Brzycki formulas
For two to ten completed reps, the Epley equation is 1RM = weight × (1 + reps ÷ 30). The Brzycki equation is 1RM = weight × 36 ÷ (37 − reps). At one rep, the calculator reports the lifted weight for both methods. At ten reps, the two formulas both return 1⅓ times the lifted weight.
The primary answer uses Epley so repeated calculations have one stable reference. Brzycki supplies a second published equation and the page reports the lower-to-higher formula range. A narrow range shows agreement between these two equations; it does not prove the person's actual maximum.
Read the percentage load table carefully
The table multiplies the Epley result by 100%, 95%, 90%, and five-point steps down to 50%. It does not assign a repetition target. Evidence across resistance-training studies shows meaningful variation between people and exercises in the repetitions completed at the same percentage of 1RM.
If you need a percentage outside those rows, use the percent solver for a custom load calculation. Round the result to a load your equipment can actually make, and treat the calculator's decimal as arithmetic precision rather than a claim that you can lift to the nearest tenth.
Exercise-specific estimate and safety limits
Use one calculation per exercise and variation. Technique, range of motion, equipment, fatigue, rest, and training history can change the relationship between a repetition set and an actual maximum. The tool does not use velocity, perceived exertion, repetitions in reserve, body weight, age, or training standards.
You do not need to attempt a maximal lift to use the estimate. It is informational and does not assess readiness, diagnose an injury, or prescribe training. If you are new to resistance training, pregnant, injured, recovering, or managing a cardiovascular, musculoskeletal, or neurologic condition, get individualized guidance from an appropriately qualified professional before max-effort testing.
Calculations run in your browser. Tool analytics record that a valid result was produced, but do not include the weight, repetition count, unit, estimates, or percentage loads you enter or calculate.
Frequently asked questions
How do I calculate my one rep max?
Enter the weight and the number of clean repetitions completed for one exercise, then select Calculate 1RM. The main result uses the Epley equation; a Brzycki estimate appears beside it so you can see how much two common equations differ.
What formulas does this 1RM calculator use?
For two to ten reps, Epley uses weight × (1 + reps ÷ 30). Brzycki uses weight × 36 ÷ (37 − reps). A completed single is reported as the lifted weight. Both are estimates rather than measurements of a future lift.
Should I use Epley or Brzycki?
Use the Epley number as this page's consistent primary estimate and read the Brzycki number as a comparison. Research indicates that equation performance varies by exercise and group, so a small difference is normal and neither result is guaranteed for one person.
Can I use this for bench press, squat, or deadlift?
Yes, but calculate each exercise separately. A set of 225 lb for five bench-press reps estimates that lift only; it does not establish the same max for a squat, deadlift, machine, or variation.
Why are reps limited to 1–10?
Prediction uncertainty grows as a set moves farther from a maximal effort, and equation accuracy varies with the exercise. This tool keeps its input to a practical low-repetition range and still labels the answer as an estimate.
Does the percentage table tell me how many reps I can do?
No. The table only multiplies the Epley estimate by percentages from 50% to 100%. People and exercises vary in how many repetitions they can perform at a given percentage, so the rows are not a workout prescription or rep guarantee.