Question 1

What is a one-rep max (1RM)?

Accepted Answer

Your one-rep max is the maximum weight you can lift for a single repetition of a given exercise with correct form. It is the gold standard measure of strength in powerlifting and strength training.

Question 2

Which formula does this calculator use?

Accepted Answer

The calculator averages the Epley and Brzycki formulas — the two most widely validated 1RM estimation methods. Averaging both reduces the overestimation error that each formula produces independently at higher rep counts.

Question 3

How accurate is the estimate?

Accepted Answer

Accuracy is highest between 1 and 6 reps, where the formulas typically estimate within 2–5% of true 1RM. Above 10 reps, accuracy decreases as individual factors like muscle fibre type have more influence.

Question 4

How do I use the percentage table for training?

Accepted Answer

80–85% of 1RM (4–5 reps) is ideal for hypertrophy and strength. 70–75% (6–8 reps) builds size. 85–95% (1–3 reps) develops maximal strength. 60–70% (8–12 reps) focuses on muscular endurance.

Question 5

Should I actually attempt my estimated 1RM?

Accepted Answer

Not necessarily. Attempting a true 1RM carries injury risk and requires proper warm-up and technique. The estimate is most useful as a training guide for setting percentages rather than a target to immediately attempt.