Current for 2026•As of: July 2026

One-Rep Max Calculator estimate maximum strength.

Enter your training weight and reps – compare Epley and Brzycki estimates

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1RM Calculator

Estimate your maximum strength (1RM) from training weight and reps — using the Epley and Brzycki formulas.

5 kg250 kg
1 reps20 reps

Most accurate in the range of 1–10 reps.

Estimated 1RM (Epley)

116.7 kg

Epley formula

116.7 kg

Brzycki formula

112.5 kg

Note: The Epley and Brzycki formulas are statistical estimation formulas, not an actual maximum strength test. Your real 1RM also depends on the exercise, technique, daily form and experience. Only attempt a true maximal lift with correct technique and, if possible, a spotter.

Calculate your 1RM: estimate maximum strength without a max attempt

The Epley and Brzycki formulas explained simply

The one-rep max (1RM) is the heaviest weight a person can lift for a single repetition of an exercise with correct technique. Since a true maximal attempt takes time, requires a proper warm-up and carries some injury risk, the 1RM is usually estimated in practice from a submaximal set – for example, from 100 kg for 5 reps.

The Epley formula (Boyd Epley, 1985) is: 1RM = weight × (1 + reps / 30). For 100 kg at 5 reps, this gives: 100 × (1 + 5/30) ≈ 116.7 kg. The Brzycki formula (Matt Brzycki, 1993) is: 1RM = weight × 36 / (37 − reps). For the same example: 100 × 36 / (37 − 5) = 112.5 kg. Both formulas usually agree within a few percent; Brzycki tends to be slightly more accurate at low rep ranges (1–6), while Epley is often preferred in the 6–10 rep range.

Validation studies on the accuracy of 1RM estimation formulas (including LeSuer et al. 1997, Journal of Strength and Conditioning Research) show that estimates are most reliable in the range of 1–10 repetitions. Above roughly 10–12 repetitions, fatigue and technique breakdown increasingly distort the assumed linear relationship between weight and rep count – the estimate then becomes noticeably less accurate and should only be treated as a rough guide.

What is the 1RM used for?

Applications in training

Training planning
Set target weights as a percentage of your 1RM (e.g. 80% for strength training, 65% for strength endurance).
Progress tracking
Regular estimates show whether your maximum strength is increasing over weeks and months.
Program comparison
Different training programs can be objectively compared by relative intensity (% of 1RM).
Injury prevention
Instead of a risky true maximal attempt, estimating from a submaximal set gives a safer point of reference.

Calculation examples

100 kg, 5 reps

100 kg, 5 reps
ItemAmount
Epley: 100 × (1 + 5/30)≈ 116.7 kg
Brzycki: 100 × 36/(37−5)112.5 kg

80 kg, 10 reps (accuracy limit)

80 kg, 10 reps (accuracy limit)
ItemAmount
Epley: 80 × (1 + 10/30)≈ 106.7 kg
Brzycki: 80 × 36/(37−10)≈ 106.7 kg

Frequently asked questions about the 1RM calculator

Epley, Brzycki and the accuracy of maximum strength estimates

The 1RM is the maximum weight a person can lift for exactly one repetition of an exercise with correct technique. It serves as a reference value for training planning, e.g. to set training weights as a percentage of the 1RM (such as 80% of 1RM for strength building).

The Epley formula (1985) is: 1RM = weight × (1 + reps / 30). The Brzycki formula (1993) is: 1RM = weight × 36 / (37 − reps). Both extrapolate the theoretical maximum weight for a single repetition from a submaximal set (e.g. 100 kg × 5 reps). Brzycki tends to give more accurate results at very low rep counts (1–6), while Epley is often preferred in the 6–10 rep range – in practice, the two usually differ by only a few percent.

Validation studies show the highest accuracy in the range of 1–10 repetitions, with deviations of only a few percent from an actually tested 1RM. Above roughly 10–12 repetitions, accuracy drops noticeably, as fatigue, technique breakdown and individual muscular endurance distort the assumed linear relationship between weight and rep count. The formulas therefore do not replace a true maximal attempt, but provide guidance for training planning.

For most people training, estimating from a submaximal set (e.g. 3–8 reps) is safer than a true maximal attempt, since injury risk increases with unfamiliar heavy loads. A real 1RM test should only be performed with properly warmed-up muscles, clean technique and ideally a spotter or expert supervision.

Many training plans define sets as a percentage of the 1RM: for example, 85–95% for maximum strength, 70–85% for hypertrophy (muscle growth) and 50–70% for strength endurance. With an estimated 1RM, you can derive these target weights without having to perform a real maximal attempt every time.

Important note

These calculations are for non-binding information only and do not replace professional tax advice. All information without guarantee. Learn more

Sources & calculation basis

Our calculations are based on the following official sources (as of: July 2026):

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