How it's estimated
This uses the well-known Epley formula: 1RM = weight × (1 + reps ÷ 30). So 100 kg for 5 reps ≈ 100 × (1 + 5/30) ≈ 117 kg. Estimates are most accurate at lower rep counts (under ~10).
Using your 1RM
Strength programs prescribe loads as a percentage of 1RM. Rough guide:
- Strength: 85–95% (1–5 reps)
- Muscle (hypertrophy): 67–80% (8–12 reps)
- Endurance: <67% (15+ reps)
The result table below your estimate shows the weight for common percentages.
Stay safe
Don't max out without a spotter and a proper warm-up. Estimating from a 3–5 rep set is safer and nearly as useful as a true test.
Limitations
The Epley formula is one of several 1RM prediction equations (others include Brzycki and Lombardi) that can disagree by a few percent on the same input — treat any formula's output as a close estimate rather than an exact number, especially the further your test set is from a true single rep.