.gsrc-container {
font-family: -apple-system, BlinkMacSystemFont, “Segoe UI”, Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
padding: 20px;
color: #333;
line-height: 1.6;
}
.gsrc-calculator {
background: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.gsrc-header {
text-align: center;
margin-bottom: 25px;
}
.gsrc-header h2 {
margin: 0;
color: #F36B21; /* Gatorade-ish Orange */
font-size: 28px;
font-weight: 700;
}
.gsrc-toggle {
display: flex;
justify-content: center;
margin-bottom: 20px;
gap: 20px;
}
.gsrc-toggle label {
cursor: pointer;
font-weight: 600;
display: flex;
align-items: center;
gap: 5px;
}
.gsrc-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
.gsrc-input-group {
margin-bottom: 15px;
}
.gsrc-input-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
font-size: 14px;
color: #555;
}
.gsrc-input-group input {
width: 100%;
padding: 12px;
border: 1px solid #ddd;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.gsrc-input-group input:focus {
outline: none;
border-color: #F36B21;
box-shadow: 0 0 0 2px rgba(243, 107, 33, 0.2);
}
.gsrc-full-width {
grid-column: 1 / -1;
}
.gsrc-btn {
background-color: #000;
color: #fff;
border: none;
padding: 15px 30px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
width: 100%;
transition: background 0.3s;
text-transform: uppercase;
letter-spacing: 1px;
}
.gsrc-btn:hover {
background-color: #333;
}
.gsrc-result-box {
margin-top: 25px;
padding: 20px;
background-color: #fff;
border-left: 5px solid #F36B21;
border-radius: 4px;
display: none; /* Hidden by default */
}
.gsrc-result-header {
font-size: 20px;
font-weight: bold;
margin-bottom: 15px;
color: #222;
border-bottom: 1px solid #eee;
padding-bottom: 10px;
}
.gsrc-metric {
display: flex;
justify-content: space-between;
margin-bottom: 10px;
font-size: 16px;
}
.gsrc-metric span {
font-weight: bold;
color: #F36B21;
}
.gsrc-recommendation {
margin-top: 15px;
background: #fff3e0;
padding: 15px;
border-radius: 4px;
font-size: 14px;
}
.gsrc-article h2 {
color: #222;
font-size: 24px;
margin-top: 30px;
margin-bottom: 15px;
border-bottom: 2px solid #F36B21;
padding-bottom: 5px;
display: inline-block;
}
.gsrc-article h3 {
font-size: 20px;
color: #444;
margin-top: 25px;
}
.gsrc-article p {
margin-bottom: 15px;
}
.gsrc-article ul {
margin-bottom: 20px;
padding-left: 20px;
}
.gsrc-article li {
margin-bottom: 8px;
}
@media (max-width: 600px) {
.gsrc-grid {
grid-template-columns: 1fr;
}
}
Sweat Rate Calculator
Calculate your hourly fluid loss to optimize hydration strategy.
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To match your sweat rate, you should aim to drink approximately 0 every 15 minutes during exercise of similar intensity.
Understanding Your Sweat Rate
Whether you are an endurance athlete, a team sports player, or a fitness enthusiast, understanding your fluid loss is critical for performance. The Sweat Rate Calculator is designed to help you determine exactly how much fluid you lose during exercise, allowing you to create a personalized hydration strategy.
Dehydration of as little as 2% of your body weight can negatively impact aerobic performance, cognitive function, and stamina. By using the formula popularized by sports science institutes like the Gatorade Sports Science Institute (GSSI), you can prevent dehydration and hyponatremia (over-hydration).
How the Calculation Works
This calculator uses a mass-balance equation to determine fluid turnover. The logic is straightforward:
- Weight Loss: The difference between your pre-exercise and post-exercise weight represents fluid loss (assuming the exercise duration isn’t long enough to lose significant fat/muscle mass).
- Fluid Intake: Any water or sports drink consumed during the session adds to your weight, masking the true amount of sweat lost. This must be added back into the calculation.
- Urine Output: If you use the restroom during the training session, that volume is fluid leaving the body that isn’t sweat, so it is subtracted from the total loss.
Step-by-Step Testing Protocol
To get the most accurate results from this calculator, follow this testing protocol:
- Weigh-In: Empty your bladder and weigh yourself wearing minimal clothing immediately before you start exercising. Record this as your Pre-Exercise Weight.
- Track Intake: Measure exactly how much fluid you drink during the workout. Using a water bottle with measurement lines (oz or ml) is recommended.
- Exercise: Perform your workout at the intensity you wish to measure (e.g., race pace). Note the duration in minutes.
- Weigh-Out: Immediately after finishing, towel off excess sweat and weigh yourself again wearing the same clothing (if dry) or minimal clothing. Record as Post-Exercise Weight.
Why Variability Matters
Your sweat rate is not a static number. It changes based on several environmental and physiological factors:
- Temperature & Humidity: Higher heat and humidity increase cooling demands, drastically raising sweat rates.
- Intensity: Harder efforts generate more metabolic heat, requiring more sweat for cooling.
- Acclimatization: As you become fitter or more acclimated to heat, your body may start sweating earlier and more profusely to cool down more efficiently.
It is recommended to test your sweat rate in different conditions (e.g., cool days vs. hot days, easy runs vs. interval sessions) to build a comprehensive hydration profile.
Hydration Strategy Recommendations
Once you know your hourly sweat rate, the goal isn’t always to replace 100% of fluid lost during the activity, as this can sometimes lead to gastrointestinal discomfort. A general guideline is to replace 80-100% of losses during long events.
The calculator provides a “per 15 minutes” guideline. Breaking down your intake into smaller, frequent sips helps gastric emptying and absorption compared to chugging large volumes infrequently.
function updateLabels(unit) {
var lblPre = document.getElementById(‘lbl-pre-weight’);
var lblPost = document.getElementById(‘lbl-post-weight’);
var lblFluid = document.getElementById(‘lbl-fluid’);
var lblUrine = document.getElementById(‘lbl-urine’);
var inputUrine = document.getElementById(‘urineOutput’);
if (unit === ‘imperial’) {
lblPre.textContent = ‘Pre-Exercise Weight (lbs)’;
lblPost.textContent = ‘Post-Exercise Weight (lbs)’;
lblFluid.textContent = ‘Fluid Consumed (oz)’;
lblUrine.textContent = ‘Urine Output (oz – optional)’;
inputUrine.placeholder = “0”;
} else {
lblPre.textContent = ‘Pre-Exercise Weight (kg)’;
lblPost.textContent = ‘Post-Exercise Weight (kg)’;
lblFluid.textContent = ‘Fluid Consumed (ml)’;
lblUrine.textContent = ‘Urine Output (ml – optional)’;
inputUrine.placeholder = “0”;
}
}
function calculateSweatRate() {
// 1. Get Input Values
var preWeight = parseFloat(document.getElementById(‘preWeight’).value);
var postWeight = parseFloat(document.getElementById(‘postWeight’).value);
var fluidConsumed = parseFloat(document.getElementById(‘fluidConsumed’).value);
var urineOutput = parseFloat(document.getElementById(‘urineOutput’).value);
var duration = parseFloat(document.getElementById(‘duration’).value);
var unitToggle = document.querySelector(‘input[name=”units”]:checked’).value;
// 2. Validation
if (isNaN(preWeight) || isNaN(postWeight) || isNaN(fluidConsumed) || isNaN(duration) || duration <= 0) {
alert("Please enter valid numbers for weights, fluid consumed, and duration.");
return;
}
// Handle optional urine output
if (isNaN(urineOutput)) {
urineOutput = 0;
}
var totalFluidLossLiters = 0;
var sweatRateLitersPerHour = 0;
// 3. Calculation Logic
if (unitToggle === 'imperial') {
// Conversion factors: 1 lb = 16 oz. Water density approx 1 lb = 16 oz (fl).
// Logic: (Pre – Post) in lbs * 16 = Weight Loss in Oz.
// Total Oz Lost = Weight Loss Oz + Fluid Consumed Oz – Urine Oz.
var weightLossLbs = preWeight – postWeight;
var weightLossOz = weightLossLbs * 16;
var totalSweatLossOz = weightLossOz + fluidConsumed – urineOutput;
// Rate per hour
var durationHours = duration / 60;
var sweatRateOzPerHour = totalSweatLossOz / durationHours;
// Formatting results for Imperial
var drinkEvery15 = sweatRateOzPerHour / 4; // 4 quarters in an hour
document.getElementById('resTotalLoss').textContent = totalSweatLossOz.toFixed(1) + " oz";
document.getElementById('resRate').textContent = sweatRateOzPerHour.toFixed(1) + " oz/hr";
document.getElementById('resDrink15').textContent = drinkEvery15.toFixed(1) + " oz";
} else {
// Metric Logic
// Weight in Kg. Fluid in mL.
// 1 kg of water = 1000 mL (approx).
var weightLossKg = preWeight – postWeight;
var weightLossmL = weightLossKg * 1000;
var totalSweatLossmL = weightLossmL + fluidConsumed – urineOutput;
// Rate per hour
var durationHours = duration / 60;
var sweatRatemLPerHour = totalSweatLossmL / durationHours;
var sweatRateLPerHour = sweatRatemLPerHour / 1000;
// Formatting results for Metric
var drinkEvery15 = sweatRatemLPerHour / 4;
document.getElementById('resTotalLoss').textContent = (totalSweatLossmL / 1000).toFixed(2) + " Liters (" + Math.round(totalSweatLossmL) + " ml)";
document.getElementById('resRate').textContent = sweatRateLPerHour.toFixed(2) + " L/hr";
document.getElementById('resDrink15').textContent = Math.round(drinkEvery15) + " ml";
}
// 4. Show Results
document.getElementById('resultBox').style.display = 'block';
}