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How to assess your One Repetition Maximum (1RM) for strength training

Nigel Hetherington explains how to assess your one-repetition maximum (1RM) for strength training.

When seeking to develop strength, power or explosiveness for your event knowing your 1RM is essential to develop the appropriate component in a structured manner i.e.

  • Working at 70 to 75% of your 1RM means you are working on muscle hypertrophy - thickening of the muscle
  • Working at 85 to 90% facilitates power development - reduced bulking
  • Efforts at 95 to 98% support explosiveness - higher recruitment levels - no bulking
  • Working much below 70% may support strength endurance but will not facilitate hypertrophy and will not make you stronger!

Not knowing in which region you are working is pointless. Furthermore, the ability to assess your 1RM for a given exercise, without having to lift that weight, has clear advantages in terms of safe practice, minimising the chance for injury and allowing those whose specific lifting technique may not yet support maximal repetitions to gain benefits.


As a fitness component, we can plan to generate measurable improvements in strength (as well as power or explosiveness) within 6 to 8 weeks. It has been understood for some years now that there is a linear relationship between the number of repetitions to exhaustion with a given resistance and the % your 1RM. A convenient formula exists to allow us to make the calculation:

Predicted IRM = Weight lifted ÷ (1.0278 - 0.0278x)

Where 'x' is the number of repetitions to exhaustion

What this means is that, say, in a half squat you can perform ten repetitions at 100kg your calculated 1RM using the equation above would be 133kg. In reality, to establish a more robust value, we will need to perform lifts to exhaustion at different resistances. Several approaches are possible:

Calculating 1RM in a session

  1. Calculate from a single set as above - a reasonable starting point but may not be accurate since if you stop at ten repetitions, you remain uncertain whether or not you could have managed 11.
  2. As above but, once the first set has been completed increase the resistance by a few % (or decrease if, say, only nine repetitions were completed) to see if ten repetitions can still be attained (can now be achieved). Repeat until exactly ten repetitions can only be obtained, and you fail on the 11th.
  3. As given below - this increases the chances of an accurate figure:
    • Start with a light to moderate resistance level you are comfortable with to rehearse the lifting technique for 8 to 10 repetitions
    • Increase the resistance to a level where you will be able only to perform around 8 to 10 repetitions to exhaustion
    • Perform the lifts. Record the resistance and the number of repetitions
    • After a minimum 3-minute recovery, increase the resistance by around 10% and repeat the lifts to exhaustion. Record the resistance and the number of repetitions
    • After a further minimum 3-minute recovery, increase the resistance by an additional 10% and repeat the lifts to exhaustion and record the resistance and the number of repetitions.


Ensure you are familiar with the lift you are about to perform and that, where appropriate, you have a 'spotter' - particularly when working with free weights.

Ensure you are fully warmed up and that the equipment is safe. You should not be fatigued when lifting. The same approach may be taken for several different lifts in one session. Treat this as a training session in itself and perform it in a warm, comfortable environment. Gently cooldown afterwards.

Do not strain when lifting - reproducible efforts with a consistent and good technique will provide the safest and most reliable adaptation.

Use the calculated 1RM to calculate appropriate loadings for hypertrophy, power or explosiveness training as given above.

Re-assess your 1RM from time-to-time as this value will change and determines the resistances used in the various workouts. Record all sessions! Devise a maintenance program once your goal is achieved.

Article Reference

This article first appeared in:

  • HETHERINGTON, N. (2005) How to assess your One Repetition Maximum (1RM) for strength training. Brian Mackenzie's Successful Coaching, (ISSN 1745-7513/ 23 / June), p. 10-11

Page Reference

If you quote information from this page in your work, then the reference for this page is:

  • HETHERINGTON, N. (2005) How to assess your One Repetition Maximum (1RM) for strength training [WWW] Available from: [Accessed

About the Author

Nigel Hetherington was the Head Track & Field Coach at the internationally acclaimed Singapore Sports School. He is a former National Performance Development Manager for Scottish Athletics and National Sprints Coach for Wales. Qualified and highly active as a British Athletics level 4 performance coach in all events he has coached athletes to National and International honours in sprints, hurdles as well as a World Record holder in the Paralympic shot. He has ten years of experience as a senior coach educator and assessor trainer on behalf of British Athletics. Nigel is also an experienced athlete in sprint (World Masters Championship level) and endurance (3-hour marathon runner plus completed the 24 hour 'Bob Graham Round' ultra-endurance event up and down 42 mountain peaks in the English Lake District). He is a chartered chemist with 26 years of experience in scientific research and publishing.