One-Rep Max Calculator
Estimate your maximum single-repetition lifting strength for bench press, squat, and deadlift using scientific Epley, Brzycki, Baechle, and Lander formulas.
Calculate 1-Rep Max & Strength Percentages (1RM = W ยท (1 + r / 30))
Enter your physical parameters below to compute verified one-rep max metrics.
Calculation Results
Calculated using verified physical methodology: Epley 1RM Formula: 1RM = W \cdot \left(1 + \r / 30\right)
Brzycki 1RM Formula: 1RM = W \cdot \36 / 37 - r
\text{85\% Working Weight (5RM): } W_{85\%} = 0.85 \cdot 1RM
Quick Summary
The One-Rep Max (1RM) Calculator evaluates maximum single-repetition lifting capacity using Epley ($1RM = W(1 + r/30)$), Brzycki ($1RM = W \36 / 37-r$), Baechle, and Lander formulas for powerlifting and bodybuilding.
Formula Explanation
Epley 1RM Formula: 1RM = W \cdot \left(1 + \r / 30\right)
Brzycki 1RM Formula: 1RM = W \cdot \36 / 37 - r
\text{85\% Working Weight (5RM): } W_{85\%} = 0.85 \cdot 1RM
How It Works
The One-Rep Max Calculator takes lifted weight ($W$) and repetitions completed ($r$). It evaluates multiple sports science 1RM formulas (Epley, Brzycki, Baechle, Lander) to compute an averaged estimated 1RM. It generates training percentage zones (95%, 90%, 85%, 80%, 75%, 70%) for resistance program design.
Step-by-Step Worked Example
Practical Problem: An athlete bench presses $W = 100.0\text{ kg}$ for $r = 5\text{ repetitions}$. Calculate estimated 1-Rep Max using Epley and Brzycki formulas and calculate 85% 5RM working weight.
- Step 1: Identify Input Parameters: Lifted Weight $W = 100.0\text{ kg}$, Reps $r = 5$.
- Step 2: Calculate Epley 1RM ($1RM = W \cdot (1 + r/30)$): $1RM = 100.0 \times \left(1 + \5 / 30\right) = 100.0 \times 1.16667 = 116.67\text{ kg (257.2 lbs)}$.
- Step 3: Calculate Brzycki 1RM ($1RM = W \cdot \36 / 37 - r$): $1RM = 100.0 \times \36 / 32 = 112.50\text{ kg (248.0 lbs)}$.
- Step 4: Average Formula Results: Average 1RM = $\116.67 + 112.50 / 2 = 114.58\text{ kg}$.
- Step 5: Calculate Training Load Percentages: 90% (3RM) = $103.1\text{ kg}$; 85% (5RM) = $97.4\text{ kg}$; 75% (10RM) = $85.9\text{ kg}$. Safe testing without injury risk!
Real-World Calculation Examples
Scenario 1: Barbell Bench Press (100 kg x 5 reps)
Parameters: $W = 100.0\text{ kg}$, $r = 5\text{ reps}$
Result: Epley 1RM = $116.67\text{ kg}$ ($257.2\text{ lbs}$), Brzycki = $112.50\text{ kg}$. Bench press 1RM.
Scenario 2: Heavy Back Squat (140 kg x 3 reps)
Parameters: $W = 140.0\text{ kg}$, $r = 3\text{ reps}$
Result: Epley 1RM = $154.00\text{ kg}$ ($339.5\text{ lbs}$), Brzycki = $148.24\text{ kg}$. Squat strength.
Scenario 3: Conventional Deadlift (180 kg x 2 reps)
Parameters: $W = 180.0\text{ kg}$, $r = 2\text{ reps}$
Result: Epley 1RM = $192.00\text{ kg}$ ($423.3\text{ lbs}$), Brzycki = $185.14\text{ kg}$. Deadlift max.
Scenario 4: Overhead Military Press (60 kg x 8 reps)
Parameters: $W = 60.0\text{ kg}$, $r = 8\text{ reps}$
Result: Epley 1RM = $76.00\text{ kg}$ ($167.6\text{ lbs}$), Brzycki = $74.48\text{ kg}$. Overhead press 1RM.
Key Benefits of Using This Calculator
Injury-Free Sub-Maximal Testing
Estimates maximum strength safely from sub-maximal 3-10 rep sets without requiring dangerous 1RM maximal attempts.
Multi-Formula Comparison
Compares Epley, Brzycki, Baechle, and Lander equations to provide an accurate averaged strength target.
Multi-Unit Readouts
Outputs 1RM in Kilograms (kg), Pounds (lbs), and percentage training zones (50%-95%).
100% Free & Client-Side
Executes locally in your browser with zero latency or web server transmission.
Frequently Asked Questions (FAQ)
What is One-Rep Max (1RM)?
One-Rep Max (1RM) is the maximum weight an individual can lift for a single rep with proper form through a full range of motion.
What is the Epley formula for 1RM?
1RM = W * (1 + r / 30), developed by Boyd Epley in 1985 for Nebraska Huskers strength programs.
What is the Brzycki formula for 1RM?
1RM = W * (36 / (37 - r)), developed by Matt Brzycki in 1993, highly accurate for reps under 10.
How accurate are 1RM calculators?
1RM formulas are most accurate when reps performed are between 2 and 10; reps above 10 shift toward muscular endurance rather than maximal strength.
Why avoid testing true 1-Rep Max in training?
True 1RM testing places extreme mechanical stress on joints, tendons, and central nervous system (CNS), raising injury risk compared to sub-maximal estimation.
How converts 1RM kilograms to pounds?
Multiply kilograms by 2.20462 (1 kg = 2.20462 lbs).
What percentage of 1RM should be used for muscle hypertrophy?
Hypertrophy training typically utilizes 65% to 80% of 1RM (8 to 12 repetitions per set).
What percentage of 1RM should be used for maximal strength?
Maximal strength programs use 85% to 95% of 1RM (1 to 5 repetitions per set).
Does muscle fiber type affect 1RM accuracy?
Yes; fast-twitch dominant lifters may lift higher actual 1RM than calculated from high reps, while slow-twitch endurance lifters complete more reps at higher percentages.
What is RPE (Rate of Perceived Exertion)?
RPE is a 1-10 scale measuring set intensity; RPE 10 means 0 reps in reserve (RIR), RPE 9 means 1 RIR.