1RM (One-Rep Max) Calculator

How to calculate 1RM (One-Rep Max) calculator?

The one-rep max estimates the maximum weight you can lift for a single repetition using the weight lifted and the number of repetitions completed.

Common formula: 1RM = weight × (1 + reps / 30)

Using the 1RM (One-Rep Max) calculator: an example

Example values: weight = 100 kg, repetitions = 5.

Step-by-step calculation:

• Record inputs: weight = 100 kg and reps = 5.
• Apply the Epley formula: 1RM = 100 × (1 + 5/30) = 100 × 1.1667.
• Compute the result: 1RM ≈ 116.7 kg; round as needed for training.
• Use percentages of 1RM (for example, 85% ≈ 99 kg) to plan training loads.

Frequently Asked Questions

Which 1RM formula should I use?

Epley and Brzycki are commonly used. Epley is simple and performs well for 1–10 reps; use the same formula consistently when tracking progress.

How accurate is an estimated 1RM?

Estimates are reasonably accurate for low rep ranges but become less reliable with high repetitions. Treat the result as a guideline rather than an exact measurement.

Should I test a true 1RM?

Direct 1RM testing gives the most precise value but requires proper warm-up, technique, and spotting for safety. Use estimated 1RM for programming when maximal testing is impractical.

Can I use kilograms or pounds?

Yes. Enter and interpret values in the same unit (kg or lb); the formula works with either unit. Convert units only when comparing across different measurement systems.