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Verified calculator with a transparent formula

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Repetition Max Calculator.

Estimates your one-rep max (1RM) and displays estimated strength for various rep ranges based on the weight lifted and number of reps performed.

Results update live as you type.
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Your inputs

How it works

  1. 1

    Enter the weight you lifted.

  2. 2

    Enter the number of repetitions you performed.

  3. 3

    The calculator estimates your one-rep max using the Epley formula.

  4. 4

    It also shows estimated weights for 5 and 10 reps.

weight * (1 + reps / 30)

Frequently asked questions

What is the Epley formula?

The Epley formula estimates your 1RM as weight × (1 + reps/30). It's a common and simple method.

How accurate is this estimate?

It's an estimate and can vary by individual. For most people it's within a few percent, but actual 1RM may differ.

Can I use this for any exercise?

Yes, it works best for compound lifts like squat, bench press, and deadlift, but can be used for any lift.

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Results

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Estimated 1RM

0kg

Estimated 5RM0kg
Estimated 10RM0kg
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Estimate for general guidance only — verify important decisions with an appropriate professional.

How it works

Estimates your one-rep max (1RM) and displays estimated strength for various rep ranges based on the weight lifted and number of reps performed.

  1. Enter the weight you lifted.
  2. Enter the number of repetitions you performed.
  3. The calculator estimates your one-rep max using the Epley formula.
  4. It also shows estimated weights for 5 and 10 reps.

Formulas

The math behind this calculator, written out so you can verify the result.

Epley Formula

1RM = weight × (1 + reps/30)

This formula estimates the maximum weight you can lift for one rep based on a submaximal set.

Real-world use cases

Where this calculation shows up in everyday life.

Training Program Design

Use your estimated 1RM to set training loads for different rep ranges.

Example: If your 1RM is 120 kg, 5 reps would be about 120 / (1 + 5/30) = 102.9 kg.

Progress Tracking

Monitor strength gains without testing a true 1RM every time.

Example: Compare estimated 1RM over weeks to see improvement.

Competition Preparation

Plan attempts for powerlifting meets based on estimated capabilities.

Example: Know your opener and second attempt weights.

Tips and common mistakes

Tips

  • Use a weight you can lift with good form for the chosen reps.
  • For best accuracy, perform the set to near failure (2-3 reps in reserve).
  • Re-test periodically as your strength changes.
  • Use the same formula consistently for tracking.

Common Mistakes to Avoid

  • Using a weight that is too light (more than 3 reps in reserve) leads to underestimation.
  • Using a weight that is too heavy (failing before the target reps) leads to overestimation.
  • Ignoring fatigue: test when well-rested for accurate results.

Assumptions and limitations

  • Use the stated inputs and units.
  • Results are estimates for planning and education.
  • Check measurements and source data before making an important decision.