One Rep Max Calculator

Percentage	Estimated Load (lb)	Epley Formula	Brzycki Formula	Typical Rep Capacity	Training Focus
100%1RM	175 lb	175 lb	168.8 lb	1 rep	Maximal Strength Testing
95%	166.3 lb	166.3 lb	160.4 lb	2 reps	Peak Strength / Power
90%	157.5 lb	157.5 lb	151.9 lb	3–4 reps	Heavy Strength Sets
85%	148.8 lb	148.8 lb	143.5 lb	5–6 reps	Strength & Hypertrophy
80%	140 lb	140 lb	135 lb	7–8 reps	Hypertrophy Baseline
75%	131.3 lb	131.3 lb	126.6 lb	9–10 reps	Volume & Muscle Growth
70%	122.5 lb	122.5 lb	118.2 lb	11–12 reps	Endurance & Hypertrophy
65%	113.8 lb	113.8 lb	109.7 lb	13–15 reps	Muscular Endurance
60%	105 lb	105 lb	101.3 lb	16–20 reps	Active Recovery & Technique

How to Use the One Rep Max Calculator

Calculating your one rep max allows you to calibrate strength cycles, plan progressive overload, and determine your working percentages without subjecting your joints and central nervous system to the taxing strain of an all-out 1-rep lift to failure. Follow these 3 simple steps:

Enter the weight you lifted: Type in the exact resistance you loaded on the barbell, dumbbells, or machine, and toggle between pounds (lb) or kilograms (kg).
Enter how many reps you completed: Enter the number of completed repetitions performed with strict, unbroken form before technical breakdown. For optimal formula accuracy, use a working set between 2 and 10 repetitions.
Click Calculate 1RM: Press the Calculate 1RM button to instantly view your predicted 1RM, side-by-side formula comparisons (Epley vs. Brzycki), and your customized 1RM percentage training chart.

What Is One Rep Max (1RM)?

A one rep max (frequently abbreviated as 1RM) is the maximum amount of weight a lifter can move for a single repetition of an exercise through a full, standard range of motion with sound biomechanical technique.

In athletic performance, strength and conditioning, powerlifting, and bodybuilding, 1RM serves as the universal benchmark for absolute dynamic strength. Rather than constantly testing maximal lifts—which carries elevated injury risks, muscular microtrauma, and prolonged systemic fatigue—coaches and athletes use submaximal repetition testing to derive an estimated 1RM. This baseline estimate is then used to program progressive overload across periodized training blocks.

Non-Medical Training Note: A 1RM calculator provides statistical approximations based on empirical exercise science equations. It is not an individualized medical evaluation or guaranteed performance promise. Always warm up thoroughly, ensure a safe lifting environment, and utilize qualified spotters or safety bars when lifting heavy loads.

How Is 1RM Calculated?

When you perform a submaximal set to failure (or near failure), the number of completed repetitions directly reflects muscular fiber fatigue. Exercise physiologists have translated this repetition-fatigue relationship into validated mathematical formulas. Our calculator calculates both major formulas side-by-side:

1Epley Formula

Created in 1985 by Boyd Epley, founder of the National Strength and Conditioning Association (NSCA), the Epley equation is the most widely adopted 1RM equation globally. It assumes that each repetition completed adds approximately 3.33% (1/30) of the weight onto the lifter's maximal potential:

1RM = Weight × (1 + Reps / 30)

Note: When Reps = 1, the formula simplifies to 1RM = Weight. The Epley formula is exceptionally reliable for heavy compound movements like the barbell bench press, back squat, and deadlift.

2Brzycki Formula

Developed in 1993 by Matt Brzycki, this equation utilizes an asymptotic relationship where the denominator contracts as repetitions increase:

1RM = Weight × 36 / (37 - Reps)

Note: When Reps = 1, 1RM = Weight × 36 / 36 = Weight. For sets between 2 and 5 reps, Brzycki and Epley deliver almost identical estimates. However, between 6 and 12 repetitions, the Brzycki equation tends to yield a slightly more conservative estimate, protecting lifters from overestimating their maximum strength.

1RM Percentage Chart

In structured strength and conditioning, training intensities are commonly prescribed as percentages of your 1RM rather than arbitrary weights. Utilizing a 1RM percentage chart enables athletes to target specific neuromuscular and hypertrophy adaptations:

90% – 100% 1RM (1 to 3 Reps)

Maximal Strength & Neuromuscular Recruitment: High central nervous system demand, ideal for peaking cycles and powerlifters testing competitive strength.

80% – 90% 1RM (4 to 7 Reps)

Heavy Strength & Mechanical Tension: The classic strength-building zone for compound barbell movements, stimulating myofibrillar hypertrophy.

70% – 80% 1RM (8 to 12 Reps)

Muscular Hypertrophy Zone: Maximizes sarcoplasmic hypertrophy and metabolic accumulation while maintaining adequate mechanical tension.

60% – 70% 1RM (13 to 20 Reps)

Muscular Endurance & Technical Deload: Suitable for speed-work, movement pattern grooving, deload weeks, and localized endurance conditioning.

*Disclaimer: These training percentage brackets are reference guidelines. They do not constitute individualized medical prescriptions or coaching orders. Individual physiology, fast-twitch vs. slow-twitch fiber dominance, and sleep recovery directly influence exact repetition ceilings.

Example One Rep Max Calculation

To understand how the math works in real-world lifting situations, examine these two verified calculations:

Example 1: 150 lb × 5 repsWorking Set

Suppose a lifter performs 150 lbs for 5 completed repetitions on the bench press.

Epley Formula:

1RM = 150 × (1 + 5 / 30)

1RM = 150 × (1 + 0.1667)

1RM = 175.0 lb

Brzycki Formula:

1RM = 150 × 36 / (37 - 5)

1RM = 150 × 36 / 32

1RM = 168.8 lb

Resulting 1RM Percentage Table (150 lb × 5 reps):

100%

175.0 lb

95%

166.3 lb

90%

157.5 lb

85%

148.8 lb

80%

140.0 lb

75%

131.3 lb

70%

122.5 lb

65%

113.8 lb

60%

105.0 lb

Example 2: 100 kg × 8 repsWorking Set

Suppose an athlete squats 100 kg for 8 continuous repetitions to full depth.

Epley Formula:

1RM = 100 × (1 + 8 / 30)

1RM = 100 × (1 + 0.2667)

1RM = 126.7 kg

Brzycki Formula:

1RM = 100 × 36 / (37 - 8)

1RM = 100 × 36 / 29

1RM = 124.1 kg

Resulting 1RM Percentage Table (100 kg × 8 reps):

100%

126.7 kg

95%

120.4 kg

90%

114.0 kg

85%

107.7 kg

80%

101.4 kg

75%

95.0 kg

70%

88.7 kg

65%

82.4 kg

60%

76.0 kg

How Accurate Is a 1RM Calculator?

While mathematical formulas provide a dependable approximation of single-rep maximums, real-world lifting performance is subject to physiological and biomechanical factors. Key variables affecting accuracy include:

Submaximal Repetition Count: Mathematical formulas are most accurate when tested in the 2 to 8 rep range. Once repetitions exceed 10 to 12 reps, aerobic conditioning, pain tolerance, and muscular endurance skew the prediction, causing formulas to overestimate true 1RM strength.
Compound vs. Isolation Movements: Equations like Epley and Brzycki were validated on multi-joint barbell movements (bench press, squat, deadlift). They are less predictive for single-joint isolation lifts (e.g. dumbbell curls or triceps extensions) where synergist muscles do not contribute.
Individual Muscle Fiber Composition: Lifters with a predominantly fast-twitch muscle fiber profile produce immense peak power for 1 to 3 reps but fatigue precipitously at higher repetitions. Conversely, slow-twitch dominant lifters might perform 10 reps at 85% of their 1RM.
Technical Consistency & Tempo: Repetitions bounced off the chest on bench press or performed with truncated squat depth will result in an artificially inflated 1RM estimate. Strict, competition-standard form is required for trustworthy estimates.

Frequently Asked Questions

Clear, practical answers to common questions about calculating one rep maxes, formula mechanics, and percentage programming.

What is a 1RM?

A one rep max (1RM) is the maximum amount of weight a person can lift for a single, full-range repetition of a given exercise with technically sound form. It serves as a benchmark for measuring absolute strength and designing percentage-based training programs.

How do I calculate my one rep max?

To calculate your one rep max without lifting a true single maximum to failure, choose a working weight you can comfortably lift for 2 to 10 repetitions with strict technique. Enter the lifted weight and completed reps into our calculator to compute your estimated 1RM using proven equations like Epley and Brzycki.

What is the Epley formula?

The Epley formula is 1RM = Weight × (1 + Reps / 30). For 1 rep, 1RM equals the lifted weight. Developed by Boyd Epley in 1985, this equation assumes that each repetition completed adds approximately 3.33% of your maximal capacity onto the base weight lifted.

What is the Brzycki formula?

The Brzycki formula is 1RM = Weight × 36 / (37 - Reps). For 1 rep, 1RM equals the lifted weight. Developed by Matt Brzycki in 1993, it provides a slightly more conservative estimate than Epley as repetition counts rise above 5 reps.

Is a 1RM calculator accurate?

A 1RM calculator provides reliable estimates when based on submaximal sets between 2 and 10 repetitions. Beyond 10 to 12 reps, accuracy declines because fatigue, lactate threshold, cardiovascular stamina, and technical breakdown skew the mathematical correlation.

Can I calculate my bench press 1RM?

Yes. You can calculate your barbell or dumbbell bench press 1RM by entering your working set weight and completed reps. Make sure your reps touched your chest with full lockout to ensure valid calculations.

Can I calculate my squat 1RM?

Yes. The calculator works for both back squats and front squats. Ensure all recorded repetitions were performed to consistent competition depth (hip crease at or below knee level) for accurate estimates.

Can I calculate my deadlift 1RM?

Yes. Conventional, sumo, and trap bar deadlifts can all be calculated. Ensure each repetition began from a dead stop on the floor without using bouncing momentum to maintain estimate fidelity.

How do I calculate 1RM from 5 reps?

With the Epley formula, a 5-rep set multiplies your weight by (1 + 5 / 30) = 1.1667. For example, 150 lbs for 5 reps gives 150 × 1.1667 = 175.0 lbs. Under Brzycki, 150 × 36 / (37 - 5) = 150 × 1.125 = 168.8 lbs.

What does 80% of 1RM mean?

80% of 1RM is a training load equal to 80 percent of your single-rep maximum. For example, if your 1RM is 200 lbs, 80% is 160 lbs. In strength training, 80% of 1RM typically corresponds to a working weight you can perform for approximately 7 to 8 repetitions.