One Rep Max Calculator

How the one rep max calculator works

Testing a true one rep max is tiring and carries some risk. Instead, you can lift a lighter weight for several reps and estimate your 1RM from that set. This calculator uses three well-known formulas and averages them.

Epley: 1RM = w × (1 + r ÷ 30) Brzycki: 1RM = w × 36 ÷ (37 − r) Lombardi: 1RM = w × r^0.10

Here w is the weight lifted and r is the number of reps done with good form.

Worked example

185 lb for 5 reps: Epley gives 185 × (1 + 5/30) = 215.8 lb, Brzycki gives 185 × 36 ÷ 32 = 208.1 lb and Lombardi gives 185 × 5^0.1 = 217.3 lb. The average is about 213.8 lb.

Getting an accurate estimate

• Use a set of 2–10 reps taken close to failure. Higher-rep sets give rougher estimates.
• Count only reps with full range of motion and good technique.
• Use a set done when fresh, not at the end of a long workout.
• Formulas work best for compound lifts such as bench press, squat and deadlift.

Using the percentage chart

Many programmes prescribe weights as a percentage of 1RM. Strength work is often 80–90% for 3–6 reps, muscle-building work 65–80% for 8–12 reps, and endurance work below 65%. The reps column is a typical range and varies between people.

Always warm up properly and use a spotter or safety bars when lifting near your maximum. Check with a doctor before starting a new training programme if you have health concerns.

Frequently asked questions

What is a one rep max?

It is the heaviest weight you can lift for a single repetition with correct form.

Which 1RM formula is most accurate?

Studies show Epley and Brzycki are both reasonable for low-rep sets. Brzycki tends to read lower at higher reps. Averaging several formulas smooths out their differences.

Can I use this for squat and deadlift?

Yes. The formulas apply to most barbell lifts. Results are less reliable for small isolation exercises like curls.

Why do the formulas give different answers?

Each was fitted to different groups of lifters. They agree closely at low reps and drift apart as reps increase.

How often should I test my 1RM?

Most lifters estimate it every 4–8 weeks from a heavy set rather than testing a true max often.