Question 1

What is a one rep max (1RM)?

Accepted Answer

A one rep max (1RM) is the maximum amount of weight you can lift for exactly one repetition of an exercise with proper form. It is used as a benchmark for strength and to calculate appropriate training loads. For example, if your 1RM squat is 100 kg, you would typically train at 70–85% (70–85 kg) for strength and hypertrophy work.

Question 2

How accurate are 1RM calculators?

Accepted Answer

1RM estimates are generally accurate to within ±5–10% of your actual maximum when based on 1–10 reps. Accuracy decreases as rep count increases — estimates from sets of 1–5 reps are more reliable than those from sets of 10+. Factors like fatigue, exercise selection, and individual muscle fibre composition also affect accuracy.

Question 3

What weight and reps should I use for the most accurate result?

Accepted Answer

For best accuracy, use a weight you can lift for 3–8 reps with good form but would struggle to complete more than 10. Avoid very high rep sets (12+) as the formula accuracy declines. A set taken to near-failure gives a better estimate than a set performed well within your capacity.

Question 4

How do I use the 1RM percentage table?

Accepted Answer

The percentage table shows training loads for different goals. 90–100% is used for maximal strength testing and competition. 80–85% is typical for strength training (3–5 reps). 70–80% is used for hypertrophy (6–12 reps). 60–70% is used for muscular endurance and volume work. Programming your training based on percentages of your 1RM allows progressive overload to be tracked objectively.

Question 5

Which 1RM formula is most accurate?

Accepted Answer

No single formula is universally best. The Epley and Brzycki formulas are the most widely used and perform well for most people at moderate rep ranges. The Mayhew formula tends to perform better at higher rep ranges. Using the average of all five formulas, as this calculator does, gives the most balanced and reliable estimate.

Question 6

How often should I re-test my 1RM?

Accepted Answer

Testing your 1RM directly carries injury risk and is taxing on the nervous system. Most athletes recalculate their 1RM using the calculator every 4–8 weeks after a new working set, rather than attempting a true max lift. Formal maximal testing is typically reserved for powerlifting or strength competitions.

🏋️ One Rep Max Calculator

🏋️ 1RM Formulas

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Why Know Your 1RM

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