Sweat Rate Calculator

The Sweat Rate Calculator estimates your hourly fluid loss based on weight changes and fluid intake. This tool helps athletes and fitness enthusiasts optimize hydration strategies to prevent dehydration. Whether you are training for a marathon, running in hot weather, or doing high-intensity interval training, this calculator provides essential data for peak performance.

Enter your weight before exercise in pounds (lbs) or kilograms (kg)
Enter your weight after exercise in pounds (lbs) or kilograms (kg)
Enter the duration of your exercise in minutes
Enter the amount of fluid you consumed during exercise in ounces (oz) or milliliters (ml)
Enter the amount of urine you passed during exercise in ounces (oz) or milliliters (ml)

How Sweat Rate Is Calculated

Sweat rate measures the volume of fluid your body loses through perspiration during physical activity. To calculate it, you must account for weight loss while adding back any fluids consumed or excreted. This method is standard in sports science for determining precise hydration needs.

[(Weight Before - Weight After) + Fluid Intake + Urine Output] / Exercise Duration

Where:

  • Weights are in pounds or kilograms
  • Fluids are in ounces or milliliters
  • Duration is in hours

First, calculate the difference between your starting and ending weight to find raw weight loss. Next, add the amount of fluid you drank and any urine you produced to this weight loss number. This step is vital because it shows the total fluid that actually left your body. Finally, divide the total fluid loss by the duration of your workout in hours. This accurate method helps you replace exactly what you lost.

This calculation is widely accepted by coaches and medical professionals for its reliability.

What Your Sweat Rate Means

Your sweat rate reveals how much water and electrolytes you need to drink to stay safe and perform well. Understanding this number helps you create a hydration plan tailored to your specific physiology.

Low (Less than 16 oz/hr)

If you fall in this range, you lose fluids slowly. This is common during light activities like yoga or walking in cool weather. Drink water when thirsty rather than forcing large amounts.

Moderate (16 oz/hr to 31.9 oz/hr)

Most gym-goers fall here. You should aim to drink about half your sweat rate during the workout, typically 12 to 16 ounces every hour, to maintain performance.

High (32 oz/hr to 47.9 oz/hr)

This rate suggests significant loss, often seen in runners or high-intensity training. You must drink consistently, around 20 to 24 ounces per hour, and consider adding electrolytes to prevent cramps.

Very High (48 oz/hr or more)

This extreme level requires aggressive management. You need to consume fluids with sodium frequently to avoid dangerous dehydration.

Important: Factors like temperature, clothing, and genetics can cause your rate to change daily. This calculator is for informational purposes only and is not a substitute for professional medical advice. Always consult a healthcare provider or sports dietitian for a comprehensive plan.

Test your rate in different seasons to adjust your strategy year-round.