Estimating your one-rep max without testing it: formulas, percentages and training weights

Your 1RM (one-rep max) is the heaviest weight you can lift once with correct technique. It is the reference for programming weights as percentages. The good news: you do not need to test it, which is risky and tiring. A set of a few reps lets you estimate it, for example with our one-rep max (1RM) calculator.

Why avoid testing your true max

• A max test needs a long warm-up and, ideally, a spotter.
• It is risky if your technique is not fully dialled in, especially on the squat and bench press.
• It depends heavily on how you feel that day: poor sleep can cost 5% or more.

An estimate from a set of 3 to 8 clean reps is almost as useful for calibrating your weights, and much safer.

The two most widely used formulas

Epley: 1RM = weight × (1 + reps / 30).

Brzycki: 1RM = weight × 36 / (37 − reps).

Example: you do 6 reps at 80 kg. Epley gives 96 kg, Brzycki 92.9 kg. The average, 94.5 kg, is a good starting estimate.

The longer the set, the less accurate the estimate. Beyond 10 to 12 reps, endurance and fatigue distort the result. Aim for 3 to 8 reps.

How reliable is it?

Expect a margin of about ±5% between 3 and 8 reps. It varies with the exercise (compound lifts like the squat estimate better than isolation moves), your profile (some people have more endurance) and how clean the reps are. Always compare the same exercise under the same conditions: the trend matters, not the exact value.

Turning your 1RM into working weights

Here is an approximate match between percentage of 1RM and reps you can do:

• 95%: about 2 reps
• 90%: about 3 reps
• 85%: about 5 reps
• 80%: about 8 reps
• 75%: about 10 reps
• 70%: about 13 reps

With a 94.5 kg 1RM, 80% gives about 75.6 kg for 8 reps. Our calculator shows the whole table.

Which percentage zone for which goal?

• Strength: 80 to 90% of 1RM, 2 to 5 reps, 2 to 4 minutes of rest.
• Muscle growth (hypertrophy): 65 to 80%, 6 to 12 reps, 1 to 3 minutes of rest, sets close to technical failure.
• Technique and getting back in: 50 to 65%, 10 to 15 reps, leaving 2 to 3 reps in reserve.

Common mistakes

• Using a set taken to failure with poor technique: the estimate will be too high.
• Applying the same percentage to every exercise: a shoulder press does not follow the same curve as a deadlift.
• Never recalculating: redo the estimate every 4 to 8 weeks as your weights change.

Putting it into practice

If you are new, start light and add weight as soon as you reach the top of the rep range on every set: this is called double progression. Our programs apply it session after session: Beginner gym program: 8 weeks to get started, Muscle gain program: 3 days a week or Upper / lower split: 4 days a week to go further.