Calculate your maximum lifting capacity and training zones.
Pounds (lbs)
Kilograms (kg)
Estimated 1RM
0
Training Percentages
Understanding Your One Rep Max (1RM)
A One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition of a specific exercise while maintaining proper form. In the world of strength training and bodybuilding, knowing your 1RM is essential for designing effective workout programs. It serves as the baseline for determining the intensity of your sets.
How This Calculator Works
Our workout calculator uses the Brzycki Formula, which is widely considered one of the most accurate mathematical models for predicting strength without the risk of lifting to absolute failure. The formula is:
1RM = Weight / (1.0278 – (0.0278 × Reps))
Training Zones Explained
Once you know your 1RM, you can target specific fitness goals by training at different percentages of that max:
Power (90-95%): Develops explosive strength and neuromuscular efficiency.
Strength (80-90%): The "sweet spot" for building raw force and muscle density.
Hypertrophy (70-80%): Ideal for muscle growth and size development.
Endurance (60-70%): Focuses on muscular stamina and cardiovascular health.
Practical Example
If you bench press 225 lbs for 5 repetitions, your estimated 1RM is approximately 253 lbs. Using this data, you would know that to train for muscle growth (80%), you should be using roughly 202 lbs for your working sets.
⚠️ Safety Note: Calculated 1RM values are estimates. Always use a spotter when attempting heavy lifts, especially when trying a weight you have never lifted before.
function calculateWorkout() {
var weight = parseFloat(document.getElementById('weightLifted').value);
var reps = parseFloat(document.getElementById('repsPerformed').value);
var unit = document.getElementById('unitType').value;
var resultDiv = document.getElementById('workoutResult');
var maxDisplay = document.getElementById('oneRepMaxDisplay');
var tableDiv = document.getElementById('percentageTable');
if (isNaN(weight) || weight <= 0 || isNaN(reps) || reps 12) {
// Formulas become less accurate above 12 reps
alert('Formulas for 1RM are most accurate for 1-12 repetitions. Above 12, results may vary.');
}
// Brzycki Formula
var oneRepMax = weight * (36 / (37 – reps));
// Formatting result
var formattedMax = Math.round(oneRepMax);
maxDisplay.innerHTML = formattedMax + ' ' + unit + '';
// Generate Percentage Table
var percentages = [
{ label: '95% (Power)', pct: 0.95 },
{ label: '90% (Max Strength)', pct: 0.90 },
{ label: '85% (Strength)', pct: 0.85 },
{ label: '80% (Hypertrophy)', pct: 0.80 },
{ label: '75% (Growth)', pct: 0.75 },
{ label: '70% (Endurance)', pct: 0.70 },
{ label: '65% (Warm-up)', pct: 0.65 },
{ label: '60% (Recovery)', pct: 0.60 }
];
var tableHTML = ";
for (var i = 0; i < percentages.length; i++) {
var calculatedWeight = Math.round(oneRepMax * percentages[i].pct);
tableHTML += '
' +
'' + percentages[i].label + ':' +
'
' +
'
' +
calculatedWeight + ' ' + unit +
'
';
}
tableDiv.innerHTML = tableHTML;
resultDiv.style.display = 'block';
// Scroll to result smoothly
resultDiv.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}