How accurate are 1RM calculators?

1RM calculators are generally accurate within 5-10% when used with rep ranges under 10. The accuracy depends on factors like training experience, muscle fiber composition, and the specific formula used. Our calculator uses 7 different formulas to give you the most comprehensive estimate.

Which 1RM formula is most accurate?

The Epley formula is most widely used and accurate for most people, especially with rep ranges of 2-10. However, different formulas work better for different individuals. Brzycki tends to be conservative, while Lombardi works well for powerlifters. Our calculator shows all 7 formulas so you can compare.

Can I use this for any exercise?

Yes, you can use 1RM calculators for any compound exercise like bench press, squat, deadlift, overhead press, and rows. The formulas are based on general strength principles that apply across exercises, though they're most accurate for compound movements.

What rep range should I use for the most accurate calculation?

For best accuracy, use rep ranges between 2-10 reps. The sweet spot is 3-8 reps where most formulas perform optimally. Avoid using very high rep ranges (15+) as the formulas become less reliable due to muscular endurance factors.

How often should I recalculate my 1RM?

Recalculate your 1RM every 4-6 weeks or whenever you notice significant strength gains. For beginners, monthly calculations work well. Advanced lifters might recalculate every 6-8 weeks. Always use recent max effort sets for the most accurate results.

About 1RM Calculator

Our Mission

We built 1RM Calculator to provide lifters with a free, accurate, and easy-to-use tool for calculating their one-rep max. No sign-ups, no paywalls, no ads—just a clean, functional calculator that helps you train smarter.

Our goal is simple: help strength athletes of all levels understand their capabilities and program their training more effectively.

Why We Built This

Accuracy Matters

We use 7 scientifically validated formulas and average them for the most accurate estimate possible. Each formula has been tested on thousands of lifters.

Built by Lifters

We're strength athletes ourselves. We understand what lifters need because we use this tool in our own training.

Safety First

Testing true 1RMs can be dangerous. Our calculator helps you estimate your max safely and provides proper warm-up protocols.

Always Free

No premium version, no hidden features. Everything is free and always will be. We believe in giving back to the community.

The Science Behind Our Calculations

Our calculator uses 7 different formulas developed by exercise scientists over decades of research:

Epley (1985): The most widely used formula, particularly accurate for 10 reps or less.
Brzycki (1993): Excellent for low rep ranges (1-10), commonly used in research.
Lombardi (1989): Uses a logarithmic approach, good for experienced lifters.
O'Conner (1989): Simple and reliable, works well for beginners.
Mayhew et al. (1992): Based on a large dataset, accurate across all rep ranges.
Wathan (1994): Exponential model that handles high reps well.
Lander (1985): Conservative estimate, good for safety.

We average all 7 formulas to provide the most balanced and accurate estimate possible.

Our Commitment

✓ Privacy: We don't track your lifts or collect personal data.
✓ Accuracy: We continuously update our formulas based on the latest research.
✓ Accessibility: Our tool works on any device, anywhere.
✓ Community: We listen to feedback and implement features lifters actually need.
✓ Education: We provide resources to help you understand and use your 1RM effectively.

Get in Touch

Have questions, suggestions, or feedback? We'd love to hear from you.