One Rep Max (1RM) Guide: How to Estimate and Use Your Max

Your one rep max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It is the foundation of percentage-based strength training programs and one of the most useful numbers to know as a lifter. The good news is that you do not need to actually test a true 1RM to benefit from knowing it. Estimation formulas let you calculate it safely from a submaximal set.

Why Your 1RM Matters

Most well-designed strength programs prescribe training loads as a percentage of your 1RM. For example, a hypertrophy block might call for sets at 65-75% of your max, while a strength block might use 80-90%. Without knowing your 1RM, you are guessing at loads, which often means training too light (wasting potential) or too heavy (risking injury and burnout). Knowing your estimated max gives you a precise framework for progressive overload.

The Seven Estimation Formulas

Several researchers have developed formulas that predict 1RM from a weight lifted for multiple reps. Each formula has slightly different strengths depending on the rep range and exercise. The most commonly used include:

• Epley — One of the most widely used. Works well for moderate rep ranges (3-10 reps).
• Brzycki — Very accurate at lower rep ranges (1-6 reps). Often used interchangeably with Epley.
• Lombardi — Uses an exponential model. Good across a broader rep range.
• Mayhew — Research-based formula popular in academic strength literature.
• O'Conner — A simpler formula that performs well in practical settings.
• Wathen — Uses an exponential curve and tends to be slightly more conservative.
• Lander — Another regression-based formula with good accuracy in the 2-10 rep range.

Our calculator averages all seven formulas for the most reliable estimate. Individual formulas can vary by 5-10%, but averaging them smooths out the differences and gives you a more trustworthy number.

Percentage-Based Training

Once you know your estimated 1RM, you can use it to structure your training with precision:

Safety Tips for Testing and Estimating

• Use estimation instead of true 1RM testing — A heavy set of 3 to 5 reps is much safer than attempting an all-out single, especially for intermediate lifters. The estimation formulas are accurate enough.
• Always warm up properly — Progressive warm-up sets are non-negotiable. Never jump straight to a heavy set.
• Use a spotter or safety bars — Especially for bench press and squats. If you train alone, set the safety pins in a power rack.
• Keep reps under 10 for best accuracy — All estimation formulas become less accurate as reps increase beyond 10. Stick to 3 to 8 rep sets for the most reliable estimates.

Disclaimer: This content is for informational purposes only and is not medical advice. Always prioritize proper form and safety when lifting heavy weights.