Your One-Rep Max (1RM) is the heaviest weight you can lift for a single clean rep on a given lift. Knowing it lets you program every other set as a % of 1RM — the language every serious strength program (5/3/1, Starting Strength, Sheiko) is written in.
How the 1RM calculator works (Epley & Brzycki)
Testing a true 1RM is exhausting and risky. Instead, we take a submaximal set (say 5 reps at 80 kg) and use the Epley formula: 1RM = weight × (1 + reps/30). We cross-check with Brzycki: 1RM = weight × 36 / (37 − reps). Reliable within ±5% for sets of 2–10 reps; less reliable above 10 reps.
How to program from your 1RM
Strength (1–5 reps): 85–95% 1RM. Hypertrophy (6–12 reps): 65–80% 1RM. Endurance (12–20 reps): 50–65% 1RM. Most well-designed programs rotate through these zones across a training week.
Common lifts to test
The big five: back squat, bench press, deadlift, overhead press, barbell row. Test each every 6–12 weeks after a proper warm-up. Don't test daily — max effort taxes the CNS and needs full recovery.
Worked example
You bench 80 kg × 5 clean reps. Epley: 80 × (1 + 5/30) = 80 × 1.167 ≈ 93 kg 1RM. Brzycki: 80 × 36 / 32 = 90 kg. Estimated 1RM: ~91–93 kg. Program 5×5 at 75% = 68 kg.
- 1Always test with a spotter or safety pins.
- 2Warm-up thoroughly: 3–4 progressively heavier sets before the top set.
- 3Retest every 8–12 weeks, not every session.
Frequently asked questions
Q1.How accurate is the Epley formula?
Within 5% for sets under 10 reps. Very high-rep sets (15+) become unreliable.
Q2.Can I test my 1RM every week?
No — CNS fatigue accumulates. Use rep-max tests (like a 3RM or 5RM) more often and reserve true 1RM for peaking phases.
Q3.Beginners — should I even calculate 1RM?
You can, but early on your 1RM changes every week. Focus on progressive overload in the 5–10 rep range and recalculate every month.
Never attempt a true 1RM without proper technique, warm-up, and either a spotter or safety equipment. Injuries at max weight are severe.