What is a one rep max (1RM)?

A one rep max (1RM) is the maximum weight you can lift for a single repetition with good form. It is the gold standard measure of strength in powerlifting and strength training. Knowing your 1RM allows you to set training weights as percentages of your maximum, which is the basis of most structured strength programs.

How accurate is a 1RM calculator?

1RM calculators are most accurate when based on 3-5 rep sets. Accuracy decreases significantly above 10 reps because different individuals fatigue at different rates. Using an average of multiple formulas (as this calculator does) reduces the error from any single formula. Expect estimates to be within 5% for most people when using lower rep ranges.

Should I ever attempt a true one rep max?

Attempting a true 1RM should only be done with an experienced spotter, proper warm-up, and good technique. For general training purposes, using an estimated 1RM from this calculator is safer and sufficient for programming. True 1RM testing is most appropriate for competitive powerlifters or strength athletes before competitions.

What percentage of 1RM should I use for hypertrophy?

For muscle hypertrophy (size), research suggests training in the range of 65-85% of 1RM, corresponding roughly to 6-15 repetitions. The 8-12 rep range at 70-80% 1RM is a common starting point for bodybuilding-style training. Both lower rep/heavier and higher rep/lighter work within the full 6-20 rep range can produce hypertrophy if taken close to failure.

What are the different 1RM formulas?

Common 1RM formulas include Epley (weight × (1 + reps/30)), Brzycki (weight × 36/(37 - reps)), Lander, Lombardi, Mayhew, O'Conner, and Wathan. Each formula was derived from studies on different populations and tends to perform differently at low vs high rep ranges. Averaging multiple formulas, as this calculator does, provides a more robust estimate than relying on any single one.

One Rep Max Calculator (1RM)

Why Track Your One Rep Max?

Your one rep max is the foundation of percentage-based strength programming. Most serious strength programs, including 5/3/1, Texas Method, and Westside Barbell, prescribe training weights as percentages of your 1RM. Knowing your 1RM for the main lifts (squat, bench press, deadlift, and overhead press) allows you to follow these programs precisely and progressively overload in a systematic way.

Tracking 1RM over time is also one of the best measures of strength progress. A rising 1RM confirms your training is working; a stalled or declining 1RM suggests you need to adjust your programming, recovery, or nutrition.

Training Percentages Guide

% of 1RM	Rep Range	Primary Training Goal
90-100%	1-3 reps	Max strength, competition prep
80-90%	3-5 reps	Strength development
70-80%	6-8 reps	Strength + hypertrophy
65-75%	8-12 reps	Hypertrophy (muscle size)
55-65%	12-20 reps	Muscular endurance, volume

Average 1RM by Experience Level

Strength standards vary considerably by bodyweight, sex, and training age. For context, a commonly used benchmark for intermediate male lifters (80-90 kg bodyweight) is a 100 kg bench press, 140 kg squat, and 180 kg deadlift. These are rough guides, not targets, as individual genetics, training history, and leverages vary enormously. What matters most is that your own 1RM increases over time.

Support your training with the right fuel using our Macro Calculator, or calculate your calorie needs with the Calorie Calculator.

One Rep Max Calculator

Training Weight by Reps

Formula Breakdown

How to Use One Rep Max Calculator

Why Track Your One Rep Max?

Training Percentages Guide

Average 1RM by Experience Level

Frequently Asked Questions

Related Tools