| Intensity | Weight |
|---|---|
| '+percentages[i]+'% of 1RM | '+pWeight+' |
How to Use the One Rep Max Calculator
The one rep max calculator is an essential tool for athletes, powerlifters, and fitness enthusiasts to estimate the maximum amount of weight they can lift for a single repetition of a specific exercise. Knowing your 1RM is crucial for designing effective strength training programs and tracking progress over time.
To find your estimated maximum, follow these steps:
- Step 1: Choose a Formula
- Select between Epley, Brzycki, or other popular formulas. The Epley formula is the most common for high-intensity lifting.
- Step 2: Enter Weight Lifted
- Input the total weight you successfully lifted (including the bar) during a set where you were close to failure.
- Step 3: Enter Repetitions
- Input the number of clean repetitions completed. For the highest accuracy, use a rep count between 2 and 10.
Why Estimate Your 1RM?
Attempting an actual one-repetition maximum can be extremely taxing on the central nervous system and poses a higher risk of injury, especially for beginners. By using our one rep max calculator, you can estimate this peak strength without the same level of physical risk.
- Program Design: Most strength programs are based on percentages (e.g., "5 sets of 5 at 80% of 1RM").
- Safety: Avoid the physical strain of maxing out every week.
- Progress Tracking: See if your "calculated max" is increasing even if you aren't testing 1RMs.
How It Works: The Mathematics of Strength
When you lift a weight for multiple reps, there is a mathematical relationship between the weight, the reps, and your ultimate potential. The two most popular formulas are:
The Epley Formula
1RM = Weight × (1 + (Reps / 30))
Developed by Boyd Epley in 1985, this formula is highly regarded in the strength and conditioning community for its simplicity and accuracy in compound movements like the squat and deadlift.
The Brzycki Formula
1RM = Weight / (1.0278 – (0.0278 × Reps))
Created by Matt Brzycki, this formula is often preferred for upper body movements like the bench press and is sometimes considered more conservative than Epley's.
One Rep Max Calculation Example
Scenario: A lifter completes 225 lbs for 5 clean repetitions on the bench press. They want to know their estimated 1RM to prepare for their next training block.
Step-by-step solution using the Epley Formula:
- Weight = 225 lbs
- Reps = 5
- Calculate (Reps / 30): 5 / 30 = 0.1666
- Add 1 to result: 1 + 0.1666 = 1.1666
- Multiply by Weight: 225 * 1.1666 = 262.5
- Estimated 1RM = 262.5 lbs
One Rep Max Percentage Chart
Once you have your 1RM, you can calculate common training weights. If your 1RM is 300 lbs, your training table would look like this:
| Percentage | Purpose | Weight (300 lb Max) |
|---|---|---|
| 100% | Absolute Peak Strength | 300 lbs |
| 90% | Maximal Strength Training | 270 lbs |
| 80% | Hypertrophy / Power | 240 lbs |
| 70% | Muscular Endurance / Speed | 210 lbs |
Common Questions
How accurate is a one rep max calculator?
While highly useful, these calculators are estimates. They are most accurate when you use a "reps to failure" count between 3 and 8. If you can perform 15 or 20 reps with a weight, the calculator becomes significantly less reliable because endurance factors begin to outweigh pure strength.
Does the formula change for different exercises?
Generally, no, but lifters often find certain formulas more "honest" for certain lifts. Epley is excellent for lower body, while many find Brzycki better for the bench press. The difference is usually minimal (within 1-3%).
Should I max out every week?
No. Maxing out frequently can lead to overtraining and plateaus. Use the one rep max calculator to estimate your progress every 4-8 weeks, and only test a true 1RM when you are peaking for a competition or a specific testing day.