Guide · Updated November 2026 · How we check our numbers

How to Estimate Your One-Rep Max Safely

Your one-rep max (1RM) is the heaviest weight you can lift once with good form. Many programs use percentages of it, but testing a true max is tiring and can be risky. Estimating it from a set of several reps is safer.

The formulas

• Epley: 1RM = weight × (1 + reps ÷ 30)
• Brzycki: 1RM = weight × 36 ÷ (37 − reps)

Lifting 100 kg for 5 reps: Epley gives 116.7 kg and Brzycki 112.5 kg — an average of about 114.6 kg.

Getting a good estimate

• Use a set of 2–10 reps taken close to failure with clean technique.
• Warm up properly first.
• Estimates are less reliable above about 10 reps.

Training with percentages

With a 100 kg max, 80% is 80 kg — roughly 7–8 reps — and 70% is 70 kg, roughly 13 reps. Heavier percentages build strength; lighter ones with more reps build muscle and endurance.

Track volume too

Training volume (sets × reps × weight) shows your total work. 4 sets of 8 at 100 kg is 3,200 kg. Increasing volume gradually over weeks — progressive overload — is how most people keep getting stronger.

Try the calculators

This guide is general information, not professional advice.