One-Rep Max Calculator

How it works

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

The two formulas agree closely around 8–10 reps; Epley gives slightly higher numbers at low reps. We show both and use their average as the headline. If you enter 1 rep, the weight itself is your 1RM.

Using percentages to program training

Many strength programs prescribe loads as a percentage of 1RM. As a rough guide, about 85% or more is typical for heavy sets of 1–5 reps (strength), 67–85% for 6–12 reps (muscle growth), and 65% or less for higher-rep endurance work. The chart in your result lists loads from 60% to 95%.

Getting an accurate estimate

• Use a set taken close to failure with good form — the formula assumes you couldn't do another rep.
• Sets of 3–10 reps give the best estimates; accuracy drops beyond 10 reps.
• Warm up thoroughly first, and use a spotter or safety bars for bench press and squats.
• Estimates are lift-specific; a squat 1RM tells you nothing about your deadlift.

Why estimates vary

Muscular endurance differs between people and lifts. Someone with more fast-twitch fibers may do fewer reps at a given percentage, so formulas can over- or underestimate. Track your own numbers over time; consistency matters more than precision.

How to perform a safe rep-max test

1. Warm up with 5–10 minutes of light cardio and a few lighter sets of the lift.
2. Choose a weight you think you can lift for about 3–8 reps with good form.
3. Perform reps steadily until you could not complete another with good technique — stop before form breaks down.
4. Rest 3–5 minutes before any further heavy sets.
5. Enter the weight and reps here.

Always use safety pins or a spotter on the bench press and squat, and never attempt maximal lifts when tired or unwell.

Choosing reps for your goal

Research shows muscle can grow across a wide range of loads when sets are taken close to failure, so these ranges are guides rather than rules.

Tracking progress with estimated 1RM

Because the estimate comes from normal training sets, you can recalculate it every few weeks without a dedicated test day. A rising estimated 1RM at the same body weight is a good sign your strength is improving. Compare like with like: the same lift, similar rep range, and similar rest before the set.

Comparing the two formulas

At 5 reps, Epley gives about 3.7% more than Brzycki; at 10 reps the two are almost identical. Epley's formula rises in a straight line with reps, while Brzycki's climbs faster as reps approach 37, which is why it is not used for very high reps. Neither is "right" — they're average fits, and individual muscular endurance varies.

Warm-up sets before a heavy set

A simple warm-up ladder before a near-max set is 2–3 sets climbing from about 40–50% to 70–80% of your expected working weight, with fewer reps as the load rises (for example 8, 5, then 3 reps).

Worked examples

Example 1: 100 kg for 5 reps

Epley = 100 × (1 + 5/30) = 116.7 kg. Brzycki = 100 × 36 / 32 = 112.5 kg. Average ≈ 115 kg.

Example 2: 225 lb for 8 reps

Epley = 225 × 1.267 = 285 lb. Brzycki = 225 × 36 / 29 ≈ 279 lb. Average ≈ 282 lb; 80% for sets of 8 ≈ 226 lb.

Limitations

• Less accurate above 10 reps and for very strong or very new lifters.
• Formulas were developed mainly on bench press and squat.
• Fatigue, sleep and technique affect any single set.

Who should not rely on this calculator

Beginners, people with heart disease or high blood pressure, pregnant people, and anyone recovering from injury should get guidance from a qualified professional before heavy or near-maximal lifting.