Rep Calculator

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One-Rep Max (1RM) Calculator

Estimated One-Rep Max

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Based on the average of Epley and Brzycki formulas

Strength Percentages Chart

Percentage Estimated Weight Typical Rep Range

Understanding Your One-Rep Max (1RM)

A One-Rep Max is the maximum amount of weight you can lift for a single repetition of a given exercise with proper form. Calculating your 1RM is essential for structured strength training programs, as most professional protocols base their intensity on percentages of your maximum strength.

How the Rep Calculator Works

The calculator uses two industry-standard formulas to provide the most accurate estimation:

  • Epley Formula: 1RM = Weight × (1 + 0.0333 × Reps)
  • Brzycki Formula: 1RM = Weight / (1.0278 – 0.0278 × Reps)

While testing your actual 1RM can be dangerous and taxing on the Central Nervous System (CNS), using sub-maximal sets (like a 3-rep or 5-rep max) allows you to estimate your strength without the same level of injury risk.

Example Calculation

If you bench press 200 lbs for 5 repetitions:

  • Epley Estimate: 200 * (1 + 0.0333 * 5) = 233.3 lbs
  • Brzycki Estimate: 200 / (1.0278 – 0.0278 * 5) = 225.0 lbs
  • Final Average Estimate: 229 lbs

Training with Percentages

Once you know your 1RM, you can program your workouts effectively:

  • Hypertrophy (Muscle Growth): 70-85% of 1RM (6-12 reps)
  • Maximum Strength: 85-95% of 1RM (1-5 reps)
  • Endurance: Below 60% of 1RM (15+ reps)
function calculateOneRepMax() { var weight = parseFloat(document.getElementById('liftedWeight').value); var reps = parseInt(document.getElementById('repetitions').value); var resultDiv = document.getElementById('repResult'); var maxDisplay = document.getElementById('mainMax'); var tableBody = document.getElementById('percentageTableBody'); if (isNaN(weight) || isNaN(reps) || weight <= 0 || reps 30) { alert("Formulas become less accurate beyond 30 repetitions. Please enter a lower rep count for a better estimate."); return; } // Formulas var epley = weight * (1 + (reps / 30)); var brzycki = weight / (1.0278 – (0.0278 * reps)); // Average var oneRepMax = (epley + brzycki) / 2; if (reps === 1) oneRepMax = weight; // Display Result maxDisplay.innerText = Math.round(oneRepMax); resultDiv.style.display = "block"; // Build Table var percentages = [ { pct: 95, reps: "2 Reps" }, { pct: 90, reps: "3-4 Reps" }, { pct: 85, reps: "5-6 Reps" }, { pct: 80, reps: "7-8 Reps" }, { pct: 75, reps: "9-10 Reps" }, { pct: 70, reps: "11-12 Reps" }, { pct: 60, reps: "15-20 Reps" } ]; var html = ""; for (var i = 0; i < percentages.length; i++) { var calculatedWeight = Math.round(oneRepMax * (percentages[i].pct / 100)); html += ""; html += "" + percentages[i].pct + "%"; html += "" + calculatedWeight + ""; html += "" + percentages[i].reps + ""; html += ""; } tableBody.innerHTML = html; }

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