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One Rep Max Calculator – Estimate Your 1RM

Estimate the most you could lift for a single repetition from a heavier set you’ve already done. Enter the weight and how many reps you completed; the calculator averages the Epley, Brzycki and Lombardi formulas and gives a percentage chart for planning your training.

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How to use the one rep max calculator

  1. Enter the weight you lifted and choose kg or lb.
  2. Enter the number of reps you completed with good form (1 to 15).

You’ll see your estimated 1RM — the average of three formulas — each formula’s result, and a table of training weights from 60% to 100% of your 1RM.

The 1RM formulas

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

Worked example

You bench press 100 kg for 5 reps:

  • Epley = 100 × (1 + 5 ÷ 30) = 116.7 kg
  • Brzycki = 100 × 36 ÷ 32 = 112.5 kg
  • Lombardi = 100 × 5^0.1 ≈ 117.5 kg
  • Average ≈ 115.5 kg

So a training set at 80% would be about 92 kg, which most people can lift about 8 times.

Percentage of 1RM and reps

% of 1RMApproximate reps
100%1
95%2
90%4
85%6
80%8
75%10
70%12
65%15
60%20

These are typical figures; people with more endurance-type muscle often manage more reps at a given percentage.

Getting a reliable estimate

  • Use a set of 3 to 6 reps — the formulas are most accurate in this range.
  • Count only good reps. Stop when your form starts to break down.
  • Test when fresh, at the start of a workout after warming up.
  • Re-estimate every few weeks as you get stronger.

Which lifts work best with 1RM estimates

The formulas were mostly developed on compound barbell lifts such as the squat, bench press and deadlift, and they work best there. For isolation exercises (curls, lateral raises) and machines, rep-based estimates are less reliable, so many people simply track the weight they can lift for a set number of reps instead. Bodyweight exercises such as pull-ups need your body weight included in the load. Whatever you use, compare like with like: the same exercise, the same range of motion and the same equipment each time.

Training with your 1RM

  • Strength: 3 to 6 reps at 80–90% of 1RM, with longer rests.
  • Muscle growth: 6 to 12 reps at 65–80%.
  • Muscular endurance: 12 or more reps below 65%.

Pair your training with enough protein using the macro calculator, and convert between kilograms and pounds with the unit converter. Lifting heavy weights carries a risk of injury; get advice from a qualified coach if you’re new to it — see our disclaimer.

Frequently asked questions

What is a one-rep max?

Your one-rep max (1RM) is the heaviest weight you can lift once with good form for a particular exercise, such as the squat, bench press or deadlift. Many training programmes set weights as a percentage of it.

How do I estimate my 1RM?

Lift a challenging weight for as many good reps as you can (ideally 2 to 10), then enter the weight and reps. If you bench 100 kg for 5 reps, the Epley formula gives about 116.7 kg and Brzycki about 112.5 kg.

Which 1RM formula is most accurate?

They agree closely for 2 to 6 reps and drift apart above 10. Averaging several formulas, as this calculator does, smooths out the differences. Accuracy also depends on the exercise and on your training history.

Is it safe to test a true 1RM?

It carries more risk than estimating. If you test it, warm up thoroughly, use a spotter or safety bars, and stop if your form breaks down. Beginners are usually better off estimating.

How do I use the percentage chart?

Programmes often prescribe sets at, say, 75% of 1RM for 10 reps or 85% for 6. The chart shows the weight for each percentage and roughly how many reps most people can do at it.

Can I use pounds?

Yes. Switch the units to lb. The formulas work the same in any unit.

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