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Calcimator

Electrolyte Replacement Calculator

Calculate sodium, potassium, and magnesium needs during exercise based on sweat rate, duration, and climate.

Inputs

L/hr
hrs
mg/L

Results

Sodium

1,350 mg

Total Fluid Needed

2.25 L

≈ 6 soda cans

Potassium300 mg
Magnesium18 mg
How to Use This Calculator
  1. Enter your Sweat Rate in liters per hour and the total Exercise Duration in hours.
  2. Input your Sweat Sodium Concentration in mg/L, or leave the ~900 mg/L average if you haven't tested it.
  3. Select the Climate you're exercising in (Cool, Moderate, or Hot) to adjust for higher sweat sodium loss in heat.
  4. Review the Sodium, Potassium, and Magnesium targets in milligrams.
  5. Use the Total Fluid Needed output to plan your hydration strategy for race day or training blocks.

How the result changes with Sweat Rate

Sweat RateSodiumTotal Fluid Needed
0.48648 mg1.08 L
1.181,593 mg2.66 L
2.022,727 mg4.55 L
2.723,672 mg6.12 L

What each input means

Sweat Rate
Your sweat rate in liters per hour (use sweat test to determine)
Exercise Duration
Total exercise duration in hours
Sweat Sodium Concentration
Sodium concentration in your sweat (average is ~900 mg/L; salty sweaters may be higher)
Climate
Environmental temperature during exercise

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Sweat Rate = 1, Exercise Duration = 1.5, Sweat Sodium Concentration = 900, Climate = 2 = 4 input(s) provided
  2. Calculate Sodium
    Sodium
    1350 = 1350
  3. Calculate Potassium
    Potassium
    300 = 300
  4. Calculate Magnesium
    Magnesium
    18 = 18

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

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