One Rep Max Calculator

Your One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise. Knowing your 1RM is essential for designing effective strength training and powerlifting programs, as most workout routines assign weights based on a percentage of your maximum capability.

Because testing a true 1RM can be physically taxing and potentially dangerous without a spotter, estimating it based on the weight you can lift for multiple reps (usually up to 10 reps) is a much safer and highly accurate alternative.

Standard Weight Percentages

Once you know your 1RM, you can map out your training zones. Here is how different percentage ranges are typically used in fitness programming:

% of 1RM	Typical Rep Range	Primary Training Goal
85% - 100%	1 - 5 reps	Maximum Strength / Powerlifting
75% - 85%	6 - 12 reps	Hypertrophy (Muscle Growth)
65% - 75%	12 - 15+ reps	Muscular Endurance

Worked Example: Hypertrophy Training

If your estimated 1RM on the bench press is 200 lbs and your program calls for 3 sets of 8 reps in the hypertrophy range, you'd target the 80% range:

Input	Value
Estimated 1RM	200 lbs
Target Percentage	80%
Working Weight	160 lbs
Prescribed Sets/Reps	3 × 8

This is the practical link between the calculator's output and an actual training session — the 1RM number itself isn't meant to be lifted regularly, it's the reference point everything else scales from.

The Formulas Behind the Estimations

Our calculator offers three of the most scientifically validated formulas for estimating a One Rep Max. While they all yield similar results, they distribute the weight curve slightly differently depending on how many reps you performed.

1. The Epley Formula (1985)

The Epley formula is widely considered the most accurate formula for standard lifts like the squat, bench press, and deadlift. It assumes a linear relationship between weight and reps.

• Formula: $$1RM = Weight \times (1 + \frac{Reps}{30})$$

2. The Brzycki Formula (1993)

The Brzycki formula is highly accurate for low repetitions (under 10). It tends to be slightly more conservative than Epley as the reps increase.

• Formula: $$1RM = Weight \times \frac{36}{37 - Reps}$$

3. The Lombardi Formula (1989)

The Lombardi formula uses an exponential curve rather than a linear one. It is often favored by powerlifters for lower body compound movements.

• Formula: $$1RM = Weight \times Reps^{0.10}$$

Important Considerations for 1RM Estimation

Repetition Cap

These formulas are generally only accurate for sets of 10 reps or fewer. Lifting a very light weight for 30 reps will not give an accurate estimation of your absolute maximal strength, since endurance factors begin to dominate the result well before that rep count.

Exercise Specificity

Your 1RM will vary wildly between exercises. An isolation movement like a bicep curl scales differently than a compound movement like a barbell squat. These formulas are best applied to heavy compound lifts, which is also why the new percentage chart below is built specifically around squat, bench, and deadlift rather than accessory movements. (For tracking the metabolic cost of these heavy sessions, you can use our Calories Burned Calculator).

Experience Level

Beginners often have a theoretical 1RM much higher than what their central nervous system can actually recruit for a true 1-rep lift. This gap tends to close with training experience, which is part of why re-testing (or re-estimating) 1RM periodically is standard practice rather than treating an early estimate as fixed.

1RM Percentage Chart by Exercise (Squat, Bench, Deadlift)

Using a 200 lb estimated 1RM as a baseline example across the three lifts most commonly programmed by percentage:

% of 1RM	Squat (200 lb 1RM)	Bench Press (200 lb 1RM)	Deadlift (200 lb 1RM)
100%	200 lbs	200 lbs	200 lbs
90%	180 lbs	180 lbs	180 lbs
80%	160 lbs	160 lbs	160 lbs
70%	140 lbs	140 lbs	140 lbs
60%	120 lbs	120 lbs	120 lbs

Because the percentage-to-weight relationship is purely mathematical, this table applies identically regardless of which specific lift you're programming — the number that changes is each lift's actual 1RM, not the percentage math itself. Use the calculator above to generate the same table using your own estimated 1RM for any lift.

One Rep Max Calculator vs Lean Body Mass Calculator: Strength vs Composition

These two numbers measure different things but are often tracked together by anyone in a structured training program. This One Rep Max Calculator measures strength output — the maximum weight you can move for a single rep on a given lift. The Lean Body Mass Calculator measures body composition — how much of your body weight is muscle, bone, and organs versus fat. Strength and lean mass are related but don't move in lockstep: it's possible to gain significant strength through improved technique and nervous-system efficiency with little change in lean mass, especially early in a training program, just as it's possible to gain lean mass without a proportional strength increase. Tracking both over time gives a fuller picture of whether progress is coming from genuine muscle growth, technique, or both.