How to estimate your one-rep max without testing it

Your one-rep max (1RM) is the heaviest weight you can lift once. Testing it is tiring and carries some risk, and most people don't need to. You can estimate it from any hard set.

The formulas

The classic ones take weight and reps and assume you went to failure:

• Epley: weight × (1 + reps ÷ 30).
• Brzycki: weight × 36 ÷ (37 − reps).
• Others (Lombardi, Mayhew, Wathan, O'Conner) differ a little, especially at high reps.

Example: 100 kg for 5 reps gives about 117 kg with Epley and 113 kg with Brzycki.

Count the reps you had left

The formulas assume failure. If you stopped with two reps in the tank, your set was really worth 7 reps to failure, not 5. Add your reps in reserve to your reps before using a formula, or the estimate will come out low.

How accurate is it?

• Most accurate from sets of 2 to 6 reps close to failure.
• Still useful up to about 10 reps.
• Unreliable past about 15 reps: endurance starts to matter more than strength.
• It varies by lift and by person, so treat it as a range, not a single number.

When to test for real

If you compete, or just want to know, test at the end of a training block after a few lighter days, with a spotter or safety bars. Work up in small jumps: about 90% of your estimate, then 96%, then the goal only if those moved well.

Tip: The trend matters more than the number. If your estimated max is climbing over months, your training is working.

Try it

The free one-rep max calculator shows your estimate from any set with every formula's answer and a reps-to-weight table. In Liftsmith, every set you log updates the estimate for that lift, using your reported effort, weighting recent and higher-quality sets more, and charting it over time.