One Rep Max Calculator: Estimated 1RM

Are one-rep max and PR the same?

One-repetition maximum, or 1RM, is the maximum load you can lift once with appropriate technique in a particular exercise. PR means personal record and may refer to one rep, five reps or another performance. The estimated 1RM shown here is not a recorded PR for a lift you have not performed.

You can use a completed set of bench press, squat, deadlift or overhead press as a starting estimate. Technique and fatigue differ across exercises. Do not transfer the result from one movement directly to another.

Entering weight and repetitions

For a barbell lift, include the bar and all plates. With dumbbells, consistently record whether you mean one dumbbell or both combined; the calculation keeps the definition of the load you enter. Choose kilograms or pounds.

The tool accepts 1–15 repetitions. Consistent technique and awareness of how demanding the set was matter. A very easy set cannot establish your exact maximum. Above ten repetitions, the result includes an additional uncertainty note. This calculator is for adults.

Epley and the single-rep case

For multiple repetitions: Epley 1RM = load × (1 + reps / 30).
For a genuine single-repetition maximum, the result is the entered load itself.

A set of 100 kg for 5 reps gives an Epley estimate of 116.7 kg. If you performed a true maximal single at 100 kg, the result is 100 kg, not 103.3 kg or an average of formulas. If that single was an easy warm-up, the calculator cannot know your remaining capacity.

Why do Brzycki and other formulas differ?

Brzycki gives 100 × 36 ÷ (37 − 5) = 112.5 kg for the same 100 × 5 set. Epley is higher in this example. The comparison also includes Lander, Lombardi, Mayhew, O’Conner and Wathan. Their average does not become the main result.

The equations describe the repetition-load relationship differently. Error can vary by exercise, person and repetition range. Research on predicting 1RM from repetition tests provides context for treating predictions cautiously. The methods are not described here as seven clinically certain formulas.

Using the training percentages

The table shows selected percentages from 50% to 95% of the main estimate. Choose your equipment’s weight increment and the loads are rounded down to it. For example, 80% of a 116.7 kg estimate is approximately 93.3 kg; with a 2.5 kg increment, the table shows 92.5 kg.

This table does not prescribe sets, repetitions, rest periods or a weekly program. Hypertrophy and strength development involve more than a percentage of 1RM. Consider your current fatigue, technique and the purpose of the session.

RPE, reps in reserve and Wilks

RPE describes perceived effort, while RIR means repetitions you believe you could still complete. This form does not ask for RIR and therefore does not adjust maximum estimates for reps in reserve. If you completed five reps but could have done five more, the result may underestimate capacity.

Strength-comparison scores such as Wilks belong to a different assessment framework. Comparing one exercise’s estimated maximum with thresholds intended for a three-lift total can wrongly label someone untrained or elite. This page does not produce those level labels.

Taking the result into training

A number on screen is not an instruction to attempt that weight immediately. Beginners should prioritize technique and controlled progression. Compare the same exercise under similar conditions over time, and keep predicted values separate from completed-lift records.

For nutrition and training context, the protein guide for athletes and muscle-building guide complement each other. Use FFMI for a body-composition index, or target heart rate to explore cardio intensity.