One-Rep Max (1RM) Calculator – Estimate Your Maximum Lift
Estimate your one-rep max (1RM) without testing it directly. Enter the weight and reps from your last working set, choose a formula, and get your estimated 1RM plus percentage-based training zones for strength programming.
How to Use This 1RM Calculator
Follow these steps to estimate your one-rep max safely:
- Enter the weight you lifted (in lbs or kg).
- Enter the number of reps you performed with that weight (1–10). The estimate is most accurate with 1–10 reps.
- Choose a formula: Epley is the most common, Brzycki is popular among powerlifters.
- Click "Calculate One-Rep Max" to see your estimated 1RM.
- Review the training zones table to plan your workouts at specific percentages of 1RM.
1RM Formulas – How They Work
Several research-backed formulas estimate 1RM from submaximal lifts:
Where w = weight lifted and r = number of reps performed. Each formula has slightly different accuracy depending on the exercise and rep range.
Examples
1RM = 225 × (1 + 5/30)
1RM = 225 × (1 + 0.167)
1RM = 225 × 1.167 = 262.4 lbs
1RM = 315 × (36 ÷ (37 − 3))
1RM = 315 × (36 ÷ 34)
1RM = 315 × 1.059 = 333.5 lbs
1RM = 405 × (1 + 2/30)
1RM = 405 × 1.067 = 432 lbs
At 90% of 1RM = 389 lbs for heavy singles; at 70% = 302 lbs for volume sets of 8–10.
Frequently Asked Questions
What is one-rep max (1RM)?
One-rep max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise with proper form. It is the gold standard for measuring muscular strength and is used to program training intensities. Instead of testing your true 1RM (which carries injury risk), you can estimate it using submaximal sets with our calculator.
Which 1RM formula is most accurate?
The Epley formula is the most widely used and well-validated, especially for rep ranges of 1–10. Brzycki tends to give slightly higher estimates and is popular in powerlifting. Lombardi can underestimate at higher rep ranges. For most lifters, Epley or Brzycki provide reliable estimates within 5–10% of a true 1RM.
How do I use 1RM for training?
Once you know your estimated 1RM, use percentages to target different training goals: 85–100% for strength (1–5 reps), 65–85% for muscle building (6–12 reps), and 50–65% for endurance (12–20+ reps). Our calculator provides a full training zones table to guide your programming.
Should beginners test their true 1RM?
Beginners should generally avoid testing their true 1RM and instead use estimated values from submaximal sets. True 1RM testing requires significant experience with the lift, a spotter, and proper warm-up. Beginners can use the estimated 1RM to guide their training and re-estimate as they get stronger. Focus on technique and consistent progressive overload first.