What is a one-rep max?

The maximum weight you can lift for a single repetition of an exercise. It is the reference for setting training loads.

How do I calculate 1RM without maxing out?

Use the Epley formula: multiply the weight by (1 + reps ÷ 30). It is most accurate at 1–12 reps.

What percentage of 1RM for muscle growth?

Generally 65–80% of your 1RM, in the 8–12 rep range, with enough total volume.

How accurate is the estimate?

A good guide, especially with low reps. Actual strength varies by lift, technique and daily fatigue.

Health & Fitness

One Rep Max Calculator (1RM)

Your one-rep max (1RM) is the most you could lift for a single rep. Rather than testing to your limit (risky), estimate it from a submaximal set — and read off the training loads for every intensity.

Your numbers

Result

Estimated 1RM

133.33

Training loads by % of 1RM
Intensity	Load
95% (2-3 reps)	126.67
90% (3-4 reps)	120
80% (8 reps)	106.67
70% (12 reps)	93.33
60% (15+ reps)	80

How the 1RM is estimated

This uses the Epley formula: 1RM = weight × (1 + reps ÷ 30). Ten reps with 100 kg gives an estimated 1RM of 133 kg. It is most accurate between 1 and 12 reps — beyond that, fatigue distorts the estimate. Switch to lb with the unit toggle if you train in pounds.

Why train by percentage of 1RM

Strength work is programmed by intensity relative to your max: maximal strength uses 85–95% (2–5 reps), hypertrophy sits around 65–80% (8–12 reps), and endurance below 60%. The table converts your 1RM into those reference loads.

Safety first

Estimating avoids the risk of a true 1RM attempt on your own. Even so, use good form, warm up properly, and have a spotter for heavy loads. The formula is an estimate — real strength varies by exercise, technique and the day.

Informational and educational result. Not a substitute for professional advice.

Frequently asked questions

Sources

Epley (1985) — 1RM estimation formula

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