What is a 1RM Calculator?
A 1RM (One-Rep Max) calculator is a tool that helps you estimate the maximum amount of weight you can lift for one repetition of a given exercise. It's an essential tool for anyone doing strength training, powerlifting, or bodybuilding. Knowing your 1RM allows you to tailor your training program with proper intensity zones and progressive overload.
How Does the 1RM Calculator Work?
Our calculator uses scientifically validated formulas including Epley, Brzycki, and Lombardi. Simply input the weight you lifted and how many reps you performed, and the calculator will estimate your one-rep max instantly.
Why Should You Know Your 1RM?
- Optimize your training intensity
- Prevent overtraining and injury
- Track your strength gains over time
- Plan %RM zones for hypertrophy, strength, and endurance
Formulas Used
Epley Formula
Best all-around 1RM calculator formula. Balanced and accurate for most training scenarios.
1RM = weight × (1 + reps / 30)
Brzycki Formula
Great for powerlifting and heavy single-rep efforts. Best accuracy at low reps.
1RM = weight × (36 / (37 − reps))
Lombardi Formula
Ideal for higher-rep sets and endurance-focused lifting programs.
1RM = weight × reps0.10
Choosing the right formula
Each 1RM formula provides a slightly different estimate based on how many reps you performed. Here’s a quick breakdown: Epley Formula – The most commonly used. Reliable and balanced for 1 to 10 reps. Great for general strength training. Brzycki Formula – Often more accurate for low reps (1–5). Ideal for powerlifting and max effort work. Lombardi Formula – Better suited for high reps. It estimates higher 1RMs for endurance-type lifting. If you're unsure, stick with Epley—it’s widely trusted and works well across most rep ranges. Just remember: for consistent progress tracking, always use the same formula each time.
Tips for Accurate Results
For best results, use rep ranges between 1–10 reps. Using too many reps can reduce formula accuracy. Also, make sure your technique is solid and consistent when lifting.
Try It Now
Use our free 1RM calculator above to estimate your one-rep max today. All free, no registration, just data you can trust.
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