One Rep Max Calculator

The One Rep Max (1RM) Calculator estimates the maximum weight you could lift for a single repetition of any exercise — the gold standard measure of strength in powerlifting and weightlifting. Knowing your 1RM lets you program workouts precisely, track progress over time, and compare your strength relative to your body weight.

This calculator uses the Epley formula, one of the most widely validated equations in sports science: 1RM = weight × (1 + reps / 30). If you perform a single rep, your 1RM is simply the weight lifted. The formula becomes increasingly accurate between 2 and 10 reps — results above 12 reps are estimates only.

Once you have your 1RM, the training percentage table gives you instant guidance on what weight to use for different rep ranges:

• 90–95% 1RM — Maximal strength work, 1–3 reps. Central nervous system training.
• 75–85% 1RM — Hypertrophy zone, 5–8 reps. Best range for muscle growth.
• 60–70% 1RM — Endurance and technique work, 10–15 reps.

Always warm up thoroughly before attempting near-maximal lifts, and consider having a spotter present. The 1RM is a training tool — never sacrifice form to hit a number.

Example

Suppose you bench press 80 kg for 5 reps. Using the Epley formula:

1RM = 80 × (1 + 5/30) = 80 × 1.167 ≈ 93.3 kg

Your estimated one rep max is 93 kg. From there, the training table tells you:

• 95% = 88.5 kg — for singles and doubles (strength peaking)
• 80% = 74.7 kg — for sets of 6 (hypertrophy)
• 70% = 65.3 kg — for sets of 10 (volume work)

Use these percentages when following structured programs like 5/3/1, Starting Strength, or any percentage-based programming to ensure every session is appropriately loaded.