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1 Rep Max (1RM) & Strength Percentage Calculator

Estimate your one-rep max from weight and reps using multiple formulas, then plan training loads with a full percentage matrix, rep-max table, and reverse weight calculator.

15 0
0 2000
1 30

Practical rounded weights for the matrix; exact calculated values are still shown.

Quick examples

1RM values calculated from submaximal sets are estimates and can vary with exercise technique, fatigue, training experience, equipment, and individual performance. Do not attempt a maximal lift solely because a calculator predicts it. Use appropriate technique, equipment, and supervision when lifting heavy loads.

Bench Press 1RM
Estimated 1RM
—

Estimated range: —

This is an estimate, not a measured 1RM.

Formula comparison

FormulaEstimated 1RMvs primary

1RM percentage matrix

% 1RMCalculatedRounded

Interactive percentage

%
40% 100%

— · rounded —

Estimated rep-max table

RepsEstimated weightRounded

Weight for target reps

1 30

Estimated weight for 8 reps: — (exact —)

Formula-based estimate — not a guarantee you can complete those reps.

Training zones (general planning)

Zone% 1RMWeightPurpose

Calculation steps

How to Calculate Your 1 Rep Max

Step-by-step method to estimate your one-rep max, build a strength percentage matrix, and plan your training loads safely.

  1. 1. Select your exercise and unit: Choose the specific lift (e.g., Bench Press, Squat) and your preferred unit of measurement (lb or kg).
  2. 2. Enter your working set data: Input the weight lifted and the number of repetitions completed in a single, hard, non-failure set.
  3. 3. Review the formula comparison: Check the estimated 1RM across multiple formulas to understand the potential range and uncertainty of the estimate.
  4. 4. Plan your training loads: Use the percentage matrix, rep-max table, and plate calculator to determine the exact weights for your upcoming workouts.

What Is a 1 Rep Max?

A one-rep max (1RM) is the heaviest load you can lift for a single complete repetition of an exercise with proper technique. Training programs often express intensity as a percentage of 1RM.

What Is a 1RM Calculator?

A 1RM calculator estimates that max from a submaximal set (weight × reps). Different formulas can produce slightly different estimates. This tool compares several common models and builds a percentage matrix for planning loads.

Epley 1RM Formula

1RM = weight × (1 + reps / 30)

Example: 200 lb × 5 reps → 200 × (1 + 5/30) = 200 × 1.1667 ≈ 233.3 lb.

Brzycki Formula

1RM = weight × 36 / (37 − reps)

Often used for lower rep ranges. This calculator only applies Brzycki within its configured valid rep range.

How Accurate Is a 1RM Calculator?

Estimates depend on reps performed, exercise, technique, fatigue, training experience, and equipment. Higher-rep sets increase uncertainty. Treat results as planning tools, not guaranteed maximal performance.

1RM Percentage Chart

Percentages of 1RM (e.g. 80%, 85%) are commonly used to organize training intensity. Actual programming varies by goal, experience, and recovery.

Bench Press, Squat & Deadlift 1RM

The same weight-and-reps formulas apply across lifts. Exercise selection here labels results (e.g. “Bench Press 1RM”) without inventing exercise-specific equations.

Common Mistakes

  • Entering a warm-up weight instead of a true working set
  • Miscounting reps or mixing lb and kg
  • Treating a high-rep estimate as precise maximal strength
  • Attempting a predicted max without proper preparation or spotting

Frequently Asked Questions

Q: What is a 1RM?

The maximum weight you can lift for one complete repetition of an exercise with proper technique.

Q: How do I calculate my 1 rep max?

Enter the weight and reps from a hard, submaximal set. This calculator applies formulas such as Epley and Brzycki and shows a comparison.

Q: What is the most accurate 1RM formula?

No single formula is universally best. Estimates differ by individual and rep range; compare several formulas and treat the result as a range.

Q: How accurate is an estimated 1RM?

Estimates are generally more reliable at lower reps (about 2–10). Higher-rep sets increase uncertainty and should be treated as rough planning tools.

Q: What does 80% of 1RM mean?

Eighty percent of your estimated one-rep max. This is a common intensity used for strength-oriented sets in periodized training programs.

Q: Can I use kilograms instead of pounds?

Yes. Switch the unit control at the top of the calculator; all values and matrices will convert automatically using standard factors.

Q: Can I estimate a 5RM from my 1RM?

Yes. Use the "Estimated rep-max table" or the "Weight for target reps" tool, which reverse-calculates the weight you should be able to lift for a specific number of reps based on your 1RM.

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