The One Rep Max Calculator is used to estimate the maximum amount of weight a person can lift for a single repetition based on submaximal lifts. Instead of testing a true maximum, which can be risky, this method relies on mathematical formulas to predict strength levels safely and consistently. It is commonly applied in resistance training, powerlifting, and general fitness planning.

A One Rep Max Calculator converts the weight lifted and the number of repetitions performed into an estimated maximum lift. This estimate helps structure training loads, monitor progress, and reduce injury risk. The calculator supports multiple formulas because strength estimation can vary depending on repetition range and individual performance.

The calculator is divided into three main areas: input fields, formula selection, and results output. Users enter the lifted weight and repetitions, choose a formula, and receive an estimated 1RM along with recommended training percentages. This structure allows consistent comparison across different estimation methods.

• Step 1: Select the unit system (kilograms or pounds).
• Step 2: Enter the weight lifted during your set.
• Step 3: Enter the number of repetitions completed.
• Step 4: Choose a calculation formula.
• Step 5: Review the estimated one-rep maximum and training percentages.

Different formulas estimate strength using distinct mathematical approaches. Below is a comparison using the same input values to show how results vary.

• Weight lifted: 100 kg
• Repetitions performed: 5

Formula: 1RM = Weight × (1 + Reps / 30)
Calculation: 100 × (1 + 5/30) = 116.7 kg
This method is widely used and provides balanced estimates for moderate repetition ranges.

Formula: 1RM = Weight × (36 / (37 − Reps))
Calculation: 100 × (36 / 32) = 112.5 kg
This formula is commonly applied in strength sports and works best with lower reps.

Formula: 1RM = (100 × Weight) / (101.3 − 2.67123 × Reps)
Calculation: ≈ 113.2 kg
It is based on research data and is often used in academic strength studies.

Formula: 1RM = Weight × Reps^0.10
Calculation: 100 × 5^0.10 ≈ 117.5 kg
This formula applies exponential scaling and may give slightly higher estimates.

Formula: 1RM = (100 × Weight) / (52.2 + 41.9 × e^{−0.055 × Reps})
Calculation: ≈ 113.6 kg
It is frequently used in sports science for trained athletes.

Formula: 1RM = Weight × (1 + 0.025 × Reps)
Calculation: 100 × (1 + 0.125) = 112.5 kg
This is a simple linear method suited for quick estimates.

Formula: 1RM = (100 × Weight) / (48.8 + 53.8 × e^{−0.075 × Reps})
Calculation: ≈ 114.9 kg
This formula accounts for fatigue and repetition decay in strength output.

The estimated 1RM represents your predicted maximum strength under ideal conditions. Values may differ slightly across formulas, which is normal. For compound lifts such as squats, bench press, or one rep max calculator deadlift estimates, consistency in formula choice is more important than the exact number.

Once the one-rep maximum is known, training loads are often planned as a percentage of that value. Lower percentages support endurance and technique, while higher percentages emphasize maximal strength development.

• All results are estimates, not guarantees.
• Accuracy decreases with very high repetition counts.
• Form, fatigue, and rest significantly affect true strength.
• Using the same formula over time improves progress tracking.

The One Rep Max Calculator provides a structured and safer alternative to maximal lift testing. It supports informed training decisions while reducing injury risk when applied correctly and consistently.