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One-Rep Max Calculator

Calculate your true one-rep max (1RM) using Epley and Brzycki formulas. Get exact percentage training loads and rep targets. 100% free, private, and instant.

Exercise (Optional) Select your lift for custom plate rounding suggestions

Weight Lifted

lbs

Enter the total weight including the barbell

Clean Repetitions Performed

reps

Submaximal sets between 1 and 10 reps give the highest accuracy

Plate Rounding Rounds percentage training loads to loadable barbell increments

🏋️

Enter the weight lifted and repetitions performed above (or click "Try an example") to calculate your safe 1-rep max and customized strength zones.

Consensus Estimated One-Rep Max (1RM)

260 lbs

Based on the mathematical average of 7 clinically validated strength formulas

Multi-Formula Breakdown

Epley Formula

262.5 lbs

Brzycki Formula

253.1 lbs

Lander Formula

255.8 lbs

Lombardi Formula

264.3 lbs

Mayhew et al.

267.8 lbs

Wathan Formula

262.3 lbs

Percentage Training Loads & Rep Targets

Load Intensity	Working Weight	Target Reps	Training Focus

How to Use This Calculator

Choose Your Lift & Units: Toggle between US (lbs) and Metric (kg), and select your primary compound lift (bench press, back squat, deadlift, or overhead press).
Enter Weight & Repetitions: Input the exact barbell weight you lifted and the number of clean, technical repetitions you completed before form breakdown.
Select Plate Rounding: Optionally round training percentages to standard barbell increments (5 lbs / 2.5 kg) so you can directly load your barbell in the gym.
Use Your Training Schedule: Review the percentage training load table to program your 5x5 heavy strength blocks, 8–10 rep hypertrophy sets, or deload weeks.

The Formulas

Estimating absolute maximum strength without attempting a dangerous 1RM lift relies on validated linear and exponential equations. GrabCalc calculates all 7 peer-reviewed formulas to eliminate individual outlier variance:

1. Epley Formula: 1RM = Weight × (1 + Reps / 30) 2. Brzycki Formula: 1RM = Weight × 36 / (37 - Reps) 3. Lander Formula: 1RM = (100 × Weight) / (101.3 - 2.67123 × Reps) 4. Lombardi: 1RM = Weight × Reps^0.10 5. Mayhew et al.: 1RM = (100 × Weight) / (52.2 + 41.9 × e^(-0.055 × Reps)) 6. O'Conner et al.: 1RM = Weight × (1 + 0.025 × Reps) 7. Wathan Formula: 1RM = (100 × Weight) / (48.8 + 53.8 × e^(-0.075 × Reps))

Where:

Weight represents the total load moved (including bar and collars).
Reps represents completed submaximal repetitions (most accurate between 1 and 10 reps).
Consensus 1RM is the arithmetic mean across all 7 equations, establishing a reliable mid-point that balances conservative equations (Brzycki) with higher-rep models (Lombardi, Mayhew).

Example: Bench Press 225 lbs for 5 Reps

Scenario: An athlete benches 225 lbs for a solid 5 clean repetitions and wants to find their true 1RM and working weight for a 5x5 program at 80% intensity.

1. Epley Calculation:
1RM = 225 × (1 + 5 / 30) = 225 × 1.1667 = 262.5 lbs

2. Brzycki Calculation:
1RM = 225 × (36 / (37 - 5)) = 225 × (36 / 32) = 253.1 lbs

3. Consensus Average:
Average across all 7 models = 259.9 lbs ≈ 260.0 lbs.

4. 80% Hypertrophy Working Weight:
260 lbs × 0.80 = 208.0 lbs (rounds to 210 lbs with standard 5 lb barbell plates).

Frequently Asked Questions

How do you calculate your one-rep max from multiple repetitions?

You calculate your 1RM mathematically using submaximal sets without needing to risk a dangerous max-lift attempt. Formulas like Epley (Weight × (1 + Reps / 30)) and Brzycki (Weight × 36 / (37 - Reps)) use empirical relationships between endurance and maximal force to predict your ultimate ceiling.

Which 1RM formula is the most accurate: Epley or Brzycki?

For low rep ranges between 1 and 5 reps, both formulas produce very similar results, with Brzycki being slightly more conservative. For sets of 6 to 10 reps, the Epley formula is often preferred because Brzycki tends to underestimate capacity as repetition count climbs higher.

Why is submaximal testing safer than a true 1RM attempt?

Testing a true 1RM places extreme structural stress on joints, connective tissue, and the central nervous system, drastically increasing the likelihood of technical breakdown and acute injury. A submaximal test (e.g. 3 to 6 reps) allows you to maintain strict form while deriving an accurate mathematical estimate.

What percentage of 1RM should you lift for muscle growth vs strength?

For maximal strength development, powerlifters typically train between 85% and 95% of 1RM for 1 to 5 repetitions. For hypertrophy (muscle building), training between 70% and 80% of 1RM for 6 to 12 repetitions provides optimal mechanical tension and metabolic stress.

Should beginners test their one-rep max?

No. Novice lifters lack the neurological motor unit recruitment patterns and movement consistency required to test absolute maximums safely. Beginners should focus on building foundational technique with 8 to 12 reps and use mathematical calculators to gauge progress.

One-Rep Max Calculator

Multi-Formula Breakdown

Percentage Training Loads & Rep Targets

How to Use This Calculator

The Formulas

Example: Bench Press 225 lbs for 5 Reps

Frequently Asked Questions

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