One Rep Max Calculator
Calculate your one-rep maximum and training weight percentages
Enter in kg or lbs (result will be in the same unit)
Best accuracy with 1-10 reps
How It Works
Overview
A one-rep max (1RM) is the heaviest weight you can lift for a single repetition with proper form. It's the standard reference point for strength programming — almost every serious lifting plan prescribes weights as a percentage of 1RM, whether you're running Starting Strength, 5/3/1, the Texas Method, or a powerlifting peak.
Testing a true 1RM is stressful and risky, so most lifters estimate it from a sub-maximal set using a regression formula. This calculator uses the Brzycki formula, the most widely cited equation in strength & conditioning literature, and returns a complete training table so you know what weight to load for any given rep range.
The Formula
Where:
- Weight = the load you actually lifted
- Reps = the number of clean repetitions to failure (or near-failure with one rep in reserve)
- 1RM = estimated single-rep maximum
Two other widely used formulas give similar results:
- Epley: 1RM = Weight × (1 + Reps / 30)
- Lombardi: 1RM = Weight × Reps^0.10
All three were derived from competition data and assume the lift was performed to genuine technical failure. Stopping 2–3 reps short of failure causes a meaningful underestimate.
Worked Example
You bench-press 100 kg for 5 strict reps:
- Brzycki: 100 / (1.0278 − 0.0278 × 5) = 100 / 0.8888 = 112.5 kg
- Epley: 100 × (1 + 5/30) = 116.7 kg
- Lombardi: 100 × 5^0.10 = 117.5 kg
Working from the Brzycki estimate of 112.5 kg, your training weights become:
- Heavy strength (90%): 101 kg for 3–4 reps
- Hypertrophy (75%): 84 kg for 9–10 reps
- Power (60%): 67.5 kg for explosive triples
When to Use This
- Programming a strength block — convert percentages from a written program into actual barbell weights.
- Tracking progress — recompute monthly from a top set; a 3–5% increase in estimated 1RM means real strength gains.
- Setting an opener for a powerlifting meet — most coaches recommend 90–93% of training-tested 1RM as a safe opener.
- Coming back from a layoff — start at 60–70% of your previous 1RM and ramp up over 3–4 weeks rather than testing cold.
- Comparing lifts across athletes — relative strength (1RM / bodyweight) lets you compare a 70 kg lifter to a 110 kg lifter fairly.
Common Mistakes to Avoid
- Estimating from a high-rep set. Above 10 reps the formulas break down. Use a 3–6 rep effort for the best estimate.
- Not lifting to true failure. Stopping with 3–4 reps left undercounts your 1RM by 5–10%. Be honest about your last rep.
- Mixing form changes mid-test. A bouncing bench or partial squat is not the same lift as a pause-and-press or below-parallel squat. Compare like to like.
- Programming at 95%+ for high volume. Spending whole sessions over 90% burns out the nervous system. Most volume should sit between 65–85%.
- Ignoring lift-specific differences. An estimated bench 1RM tells you nothing about your deadlift. Each main lift needs its own estimate.
Frequently Asked Questions
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