One Rep Max Calculator (1RM)

A one-repetition maximum, or 1RM, is the greatest load you can lift once for a particular exercise using the intended technique and range of motion. An estimated 1RM uses a recorded set of several repetitions to approximate that single-repetition maximum.

The estimate belongs to that lift and set. A bench press estimate does not establish your squat, deadlift or overhead press strength. This calculator labels each exercise separately and applies the chosen mathematical formula without inventing adjustments between exercises.

1. Select the exercise you performed and choose kilograms or pounds.
2. Enter the load you lifted, including the bar and plates when recording a barbell lift.
3. Enter 1–10 completed repetitions and choose Epley, Brzycki or Lombardi.
4. Read the estimate, compare the methods and review the mathematical percentage chart.

Use a set representative of your ability at that repetition count; an easy set with many repetitions still in reserve does not describe your limit. Do not attempt a heavier lift simply to improve the estimate. Optional rounding changes only the percentage weights, using an increment you specify for your equipment.

Multiply the recorded weight by a repetition-based factor. For 80 kg and five repetitions, the Epley factor is 1 + 5/30 = 1.166666… . Multiplying gives 93.333333… kg, displayed as an estimated 93.33 kg.

For a completed single repetition, this tool returns the lifted weight unchanged for every method. A 100 kg single therefore displays 100 kg, rather than inflating it through the unadjusted Epley equation. It still does not prove the recorded single was your heaviest possible lift.

Estimated 1RM = weight × (1 + repetitions / 30)

For 80 kg × 5 reps: 80 × (1 + 5/30) = 93.33 kg when rounded to two decimals. Epley is the initial method in this calculator. For repetitions above one, its multiplier increases linearly with repetition count; that mathematical pattern is not a guarantee that everyone’s strength follows the same relationship.

Estimated 1RM = weight × 36 / (37 − repetitions)

For 80 kg × 5 reps, the denominator is 32: 80 × 36 / 32 = 90 kg. The supported 1–10 repetition range keeps the denominator well away from zero. Counts above 10 are explained and rejected rather than silently extending the estimate toward the equation’s singularity at 37.

The same 80 kg five-repetition set gives 93.33 kg with Epley, 90 kg with Brzycki and approximately 93.97 kg with Lombardi. Lombardi uses weight × repetitions^0.10, so its growth with repetition count differs from the other two equations.

The comparison bars show the estimates for your entered set. They do not rank the methods by personal accuracy, and the spread is not a statistical confidence interval. Selecting a method changes the main estimate and the percentage chart; it does not change the recorded load or repetitions.

Select Bench Press and record a bench press set, such as 80 kg for five completed reps. The default Epley calculation labels the answer “Estimated Bench Press 1RM” and gives 93.33 kg. Switching to Brzycki gives 90 kg for the same input.

Record comparable technique, range of motion and equipment when comparing sets over time. Assistance from a spotter, a different movement standard or a change in exercise setup can make two entries represent different tasks. Use appropriate supervision and spotting for the lift you perform.

Choose Squat or Deadlift and enter a completed set from that lift. A squat set of 100 kg for five reps gives an Epley estimate of 116.67 kg. A deadlift set of 120 kg for five reps gives 140 kg. Those results come from the entered sets, not from multiplying a bench press estimate.

Overhead Press and Other / Custom Exercise work the same way. The custom name is a report label. Whether a general repetition equation is useful for a particular movement still depends on the exercise and how the set was performed.

The chart multiplies the selected, unrounded estimate by 50%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% and 100%. For a 100 kg reference, 80% is 100 × 0.80 = 80 kg. For the 93.333333… kg Epley example, 80% is approximately 74.67 kg.

Rounding to a 2.5 kg total-load increment makes that second example 75 kg. The precise percentage and rounded weight remain separate, and the underlying 1RM stays unchanged. You can specify a different increment, such as 1 kg or 5 lb. This does not assume which plates you own or prescribe a number of sets and reps.

For other percentage calculations, use the published Percentage Calculator.

Prediction error depends on the lifter, movement, repetition count and effort of the recorded set. Technique, fatigue and training experience can also change the relationship between a repetition set and a single heavy lift. More displayed decimal places do not make an estimate a precise strength measurement.

A bench press validation study by Whisenant and colleagues examined prediction equations in collegiate football players and found that validity depended on repetition count. Results from that population should not be treated as universal guarantees. This tool limits the input to 1–10 completed reps and presents alternative methods without declaring a universal winner.

Maximal testing has injury risks. Beginners can use the arithmetic to understand a recorded set, but should not interpret the output as permission to attempt an unfamiliar maximum. Appropriate technique, coaching, supervision and spotting matter.

One pound is exactly 0.45359237 kilograms. The calculator stores physical weight in kilograms and uses that relationship to show pounds. Switching the weight unit converts the entered load and rounding increment while retaining their underlying values.

A 100 kg reference is approximately 220.46 lb. Converting units changes the number used to describe the weight, not the weight itself or your strength. Visit the Sports & Fitness category for published sports calculators.