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Health & BiophysicsEntry № 02.11Documented Formula

One Rep Max (1RM) Strength Calculator

Estimates the maximal lifting capacity (1RM) from submaximal repetitions using the verified Epley and Brzycki strength formulas.

Popular Searches:Calculate 1RM from 8 reps of 80 kgEpley formula for bench press maxRep percentage chart for weightlifting
One Rep Max (1RM) Biomechanical Strength Estimator
80 kg
8 Reps
Estimated 1RM (Epley Formula)
101.3 kg

Brzycki Benchmark: 99.3 kg

Training Percentages
95%96.3
90%91.2
85%86.1
80%81.1
75%76.0
70%70.9
65%65.9
60%60.8
Mathematical Proof & FormulaStandard Mathematical Notation

How This Calculation Formula is Formulated

Biomechanical equations predicting maximal muscular lifting capacity (1 Repetition Maximum) from submaximal repetitions performed to failure.

Standard Algebraic Representation
1RM_Epley = W · (1 + r / 30) ; 1RM_Brzycki = W · [36 / (37 − r)]
Documented algebraic formula with transparent derivation and reference notes.

Variable Definitions & Measurement Units

W
Weight Lifted
Resistance load lifted during test.
r
Reps Completed
Number of full, clean repetitions performed (1 to 12).
Step-by-Step Calculation Example

8 Reps of 80 kg Bench Press

An athlete bench presses 80 kg for 8 clean repetitions to estimate their 1RM.

1
Epley Formula
80 × (1 + 8/30) = 80 × 1.2667 = 101.3 kg
Epley estimate
2
Brzycki Formula
80 × [36 / (37 − 8)] = 80 × (36 / 29) = 99.3 kg
Brzycki estimate
3
Consensus Average
(101.3 + 99.3) / 2 = 100.3 kg
Predictive consensus
Conclusion: The estimated 1RM is 101.3 kg (Epley) and 99.3 kg (Brzycki), setting working sets of 80% 1RM at 81 kg.
In-Depth Editorial Analysis

Why Submaximal 1RM Testing Protects Against Injury

Testing a true 1RM imposes extreme neural fatigue and significant joint injury risk on the lumbar spine, shoulders, and knees, especially for non-competitive lifters.

Using a 3-rep to 8-rep submaximal set with the Epley equation delivers accuracy within 2% to 3% of actual 1RM without the orthopedic risks of maximal loading.

Frequently Asked Questions

Frequently Asked Questions About One Rep Max (1RM) Strength Calculator

Up to how many repetitions is 1RM formula accurate?

Formulas are highly accurate up to 10 repetitions. Beyond 10 reps, muscular endurance and cardiovascular capacity confound pure strength estimation.

What percentage of 1RM builds hypertrophy?

Hypertrophy training typically utilizes 65% to 80% of 1RM (8 to 12 reps), while pure strength development focuses on 85%+ of 1RM (1 to 5 reps).

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Deterministic Precision & 100% Client-Side Privacy

All calculations execute in your local browser using IEEE 754 double-precision floating-point arithmetic. Your figures and financial metrics remain private and are never uploaded or saved to any cloud servers.