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Calcimator

Rehydration Calculator

Calculate sweat loss, sweat rate, and rehydration needs based on pre/post exercise weight and fluid intake.

Inputs

lbs
lbs
oz
min

Results

Total Sweat Loss

48 oz

≈ 12 sticks of butter

Rehydration Target

48 oz

≈ 12 sticks of butter

Sweat Rate48 oz/hr
Rehydrate Over2 hrs
Dehydration %1.2%
How to Use This Calculator
  1. Weigh yourself before and after exercise and enter both values in kg.
  2. Input the total fluid consumed during the session.
  3. Set the exercise duration in minutes and environment temperature.
  4. Review the Sweat Rate in liters per hour and the Total Fluid Deficit.
  5. Multiply the Fluid Deficit by 1.5 and drink that amount over the next 2 to 4 hours to fully rehydrate.

How the result changes with Pre-Exercise Weight

Pre-Exercise WeightTotal Sweat LossRehydration Target
11216 oz0 oz
192400 oz576 oz
2881,936 oz2,880 oz
3683,216 oz4,800 oz

What each input means

Pre-Exercise Weight
Weigh yourself right before exercise (minimal clothing)
Post-Exercise Weight
Weigh yourself right after exercise (towel off sweat first)
Fluid Consumed During
Total fluid consumed during exercise
Exercise Duration
Total exercise time in minutes

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Pre-Exercise Weight = 170, Post-Exercise Weight = 168, Fluid Consumed During = 16, Exercise Duration = 60 = 4 input(s) provided
  2. Calculate Total Sweat Loss
    Total Sweat Loss
    48 = 48
  3. Calculate Rehydration Target
    Rehydration Target
    48 = 48
  4. Calculate Sweat Rate
    Sweat Rate
    48 = 48
  5. Calculate Rehydrate Over
    Rehydrate Over
    2 = 2

Engine last updated . Checked against 1 independently-derived test — how we verify calculators.

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