How do I calculate my one rep max?

The most common formula is the Epley formula: 1RM = Weight × (1 + Reps/30). For example, if you lift 80kg for 8 reps: 1RM = 80 × (1 + 8/30) = 80 × 1.267 = 101.3kg. Our calculator uses 6 different formulas and averages them for accuracy.

Is the one rep max calculator accurate?

1RM calculators are most accurate when using 3-6 rep sets. Accuracy decreases with higher rep sets (above 10). The Brzycki formula is generally considered most accurate for sets under 10 reps. We average 6 formulas to minimise individual formula error.

One Rep Max Calculator — Free 1RM Strength Tool (2026)

🏋️ One Rep Max (1RM) Calculator

6 validated formulas · Average 1RM · Training percentage chart · Strength level

Weight Lifted (kg)

Reps Performed

Exercise (optional)

Bodyweight (kg) — for strength level

⚠️ Most accurate for sets of 1–6 reps. Accuracy decreases above 10 reps. Never attempt a true 1RM without a spotter.

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kg 1RM

Formula Comparison

Epley—

Brzycki—

Lander—

Lombardi—

Mayhew—

O'Conner—

📈 Training Percentages

⚠️ Never attempt a true 1RM without an experienced spotter. Use calculated 1RM for programming only.

One Rep Max — Complete Guide

Your one-rep maximum (1RM) is the maximum weight you can lift for a single complete repetition of an exercise. It is the foundation of strength training programming — knowing your 1RM allows you to set precise training intensities for different adaptations.

Why 1RM Matters for Programming

% of 1RM	Reps Possible	Primary Adaptation	Best For
95–100%	1–2	Max strength, neural	Powerlifting, peaking
85–95%	2–5	Strength + neural	Strength blocks
75–85%	5–8	Strength + hypertrophy	Most strength training
65–75%	8–12	Hypertrophy (muscle size)	Bodybuilding, building
50–65%	12–20	Muscular endurance	Endurance athletes
Below 50%	20+	Endurance, technique	Warm-ups, technique

The 6 Formulas Explained

Epley (1985): Most widely used. 1RM = w × (1 + r/30). Slightly overestimates at low reps.
Brzycki (1993): Best for sets under 10 reps. 1RM = w × (36/(37-r)).
Lander (1985): 1RM = (100 × w)/(101.3 - 2.67123 × r). Good all-rounder.
Lombardi (1989): 1RM = w × r^0.1. Slightly conservative.
Mayhew (1992): 1RM = (100 × w)/(52.2 + 41.9 × e^(-0.055 × r)). Good for higher reps.
O'Conner (1989): 1RM = w × (1 + 0.025 × r). Most conservative estimate.

Frequently Asked Questions

Never test a true 1RM without an experienced spotter, especially on bench press and squat. Warm up thoroughly: 10 minutes cardio, then 3-4 progressively heavier sets. Rest 3-5 minutes between heavy attempts. Use our calculator instead — it is safer and accurate within 5% for most people.

For most people, retesting 1RM every 8–12 weeks at the end of a training block is appropriate. More frequent testing is counterproductive — your 1RM changes slowly and frequent max attempts add significant fatigue without useful information. Use this calculator after any working set to estimate progress.

Strength standards relative to bodyweight: Beginner men can bench press their bodyweight (1× BW). Intermediate: 1.25–1.5× BW. Advanced: 1.5–2× BW. Elite/powerlifter: 2×+ BW. For women: Beginner 0.5–0.75× BW. Intermediate: 0.75–1.0× BW. Advanced: 1.0–1.25× BW.