One Rep Max (1RM) Calculator
This free 1 rep max calculator estimates the heaviest weight you can lift for a single repetition — your one-rep max — from any hard working set. Enter the weight and reps you lifted, pick the Epley or Brzycki formula, and get your estimated 1RM plus a training chart of working weights for 50–95% of your max.
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Enter a weight and rep count to estimate your 1RM.
How to use this calculator
Think back to your most recent hard set on the lift — ideally one you took close to failure — and enter the weight (total load, bar included) and the reps you completed. Use the lb/kg toggle if you train in kilos. Your estimated 1RM updates instantly as you type or drag the reps slider.
Below your 1RM you'll see a training percentage chart: the weight to load for 95%, 90%, 85%, 80%, 75%, 70%, 60%, and 50% of your max, with the typical rep range for each zone. Use it to plan heavy, moderate, and volume sets without guessing.
How it works
Both formulas predict your one-rep max from submaximal work — a weight you lifted for more than one rep:
- Epley: 1RM = weight × (1 + reps ÷ 30). For example, 225 lb × 5 reps → 225 × (1 + 5/30) = 262.5 lb.
- Brzycki: 1RM = weight ÷ (1.0278 − 0.0278 × reps). For the same set, 225 ÷ (1.0278 − 0.139) ≈ 253.2 lb.
The two formulas agree closely for sets of 1–10 reps and only start to differ meaningfully above that, where Epley tends to run a little higher. Both assume a near-maximal effort — an easy set of 12 you could have doubled will underestimate nothing and overstate your max.
Important: these are estimates only. No formula accounts for your technique, fatigue, or individual strength curve. Actual max attempts should be done with a spotter or coach, proper warm-up sets, and safety equipment.
Frequently asked questions
Which 1RM formula is most accurate?
Both the Epley and Brzycki formulas are widely used and give very similar results in the 1–10 rep range, usually within a few pounds of each other. Brzycki tends to be slightly more conservative (lower) at higher rep counts, while Epley can overestimate a little for sets of 8–12 reps. No formula can predict your true max perfectly because strength is influenced by technique, fatigue, and muscle fiber type — treat both as estimates.
How many reps should I use for the most accurate estimate?
Use a set you took close to failure in the 3–8 rep range. Fewer than 3 reps is nearly a true max test, and above 10 reps the formulas become much less reliable because muscular endurance skews the math. A heavy set of 5 reps is the classic sweet spot for an accurate 1RM estimate.
Is 1RM testing safe?
A true 1RM attempt is the riskiest kind of lift, so it should always be done with a spotter or coach, proper warm-up sets, and ideally on equipment with safety catches. A safer alternative is exactly what this calculator does: lift a heavy weight for 3–5 reps and estimate your max from that set instead of testing it directly.
Can I use this for squat, bench, and deadlift?
Yes — the Epley and Brzycki formulas work for any compound barbell lift. Just base each estimate on a recent hard set of that specific exercise. Your calculated 1RM for squat does not carry over to bench press, so estimate each lift separately and recalculate as you get stronger.