One Rep Max (1RM) Calculator
Estimate your one-repetition maximum for any weightlifting exercise.
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Estimate Your True Strength with a One-Rep Max Calculator
Our One-Rep Max (1RM) Calculator helps you estimate the maximum weight you can lift for a single repetition, a key metric for structuring your strength training program.
What is a One-Rep Max Calculator?
A One-Rep Max (1RM) Calculator is a tool for weightlifters and athletes to estimate the maximum amount of weight they can lift for a single repetition of an exercise. Actually performing a one-rep max lift can be risky and requires proper preparation. This calculator provides a safe and reliable alternative by using a sub-maximal lift (a weight you can lift for multiple reps) to predict your 1RM using established formulas.
How It Works: Common 1RM Formulas
The calculator uses several widely recognized formulas to provide an accurate estimate:
Epley Formula: 1RM = Weight × (1 + Reps / 30)
Brzycki Formula: 1RM = Weight × (36 / (37 - Reps))
Lombardi Formula: 1RM = Weight × Reps^0.10
Interpreting Your Training Percentages
The main result is your **Estimated One-Rep Max**. The calculator also provides a table of percentages based on this 1RM. This is the most practical part of the tool, as most strength training programs prescribe lifts based on a percentage of your 1RM (e.g., "5 reps at 85% of your 1RM"). This table gives you the exact weights you should be using for your workouts to ensure you are training with the right intensity to make progress.
Frequently Asked Questions
How do you calculate your one-rep max (1RM)?
Your one-rep max can be estimated using formulas that take the weight you lifted and the number of repetitions you completed (ideally 10 or fewer). Common formulas include Epley, Brzycki, and Lombardi. Our calculator uses these formulas to provide a reliable estimate of your maximal strength without requiring you to perform a risky 1RM attempt.
Why is knowing your 1RM important?
Knowing your one-rep max is crucial for designing an effective strength training program. Most programs base their intensity on a percentage of your 1RM (e.g., lifting at 80% of your 1RM for a set of 5 reps). This ensures you are lifting heavy enough to stimulate muscle growth and strength gains.
Which 1RM formula is the most accurate?
The Epley formula is one of the most commonly used and widely accepted formulas for estimating 1RM. However, the accuracy of any formula decreases as the number of repetitions increases. It's most accurate for lifts performed in the 2-6 rep range.
How often should I test my 1RM?
You should re-calculate your estimated 1RM every 4-8 weeks to ensure your training program is adjusted for your new strength levels. As you get stronger, the weights you lift should increase proportionally to continue making progress.
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