salz.run
Built by Sean Trail runner · Heavy sweater · First 100K, 2027

Build your own
electrolyte
drink, by the gram.

I'm a heavy sweater training for my first 100K, and the commercial mixes were eating my budget. salz.run is the calculator I built for myself. Plug in your sweat rate, get a per-bottle recipe, weigh five cheap ingredients on a kitchen scale. About a quarter a bottle instead of two bucks. That's the whole thing.

Inputs

Body weight
70kg
40130
Sweat loss / hour
0.90kg/hr

Net weight loss per hour of activity. 1 kg sweat ≈ 1 L fluid.

0.22.5
LightModerateHeavyElite

Classification: Moderate sweater

How to measure
  1. 01. Weigh nude before activity.
  2. 02. Train at race intensity for a known time (60+ min ideal).
  3. 03. Track fluid drunk during the session (mL).
  4. 04. Towel off, weigh nude again.
  5. 05. Sweat rate (L/hr) = (Δ kg + fluid L) ÷ hours
Session duration
2hrs
Sweat saltiness

Salty crust on cap or stinging eyes mid-effort? Bump up one.

Heat exposure
Carb intensity
Tartness

Citric acid for sour/tangy flavor. Pure mineral mix tastes flat; a pinch brightens it.

Bottle size
f(x)

Per Batch

3 × 500 ml

Total electrolytes for the session. Mix the batch, then split evenly across 3 bottles. Use a kitchen scale (0.01 g resolution) for the minerals.

Table salt (NaCl)
3.13 g
≈ 1/2 tsp
Potassium chloride (KCl)
0.76 g
≈ 1/8 tsp
Magnesium citrate (Calm)
0.38 g
≈ 1/8 tsp
Dextrose (glucose)
133.3 g
≈ 11.1 tbsp
Citric acid (flavor)
0.75 g
≈ 1/8 tsp
Water
1500 ml

Per Bottle

500 ml each

What ends up in each bottle you carry on the run.

Table salt (NaCl)
1.04 g
≈ 1/8 tsp
Potassium chloride (KCl)
0.25 g
≈ 1/8 tsp
Magnesium citrate (Calm)
0.13 g
≈ 1/8 tsp
Dextrose (glucose)
44.4 g
≈ 3.7 tbsp
Citric acid (flavor)
0.25 g
≈ 1/8 tsp
Water
500 ml
Per hour
1.4
bottles to drink
Fluid675 ml
Na553 mg
CHO60 g
Session total
3
bottles to prep
Fluid1.4 L
Na1106 mg
CHO120 g
!
Sanity check. Sodium concentration of this formula: 819 mg/L. Carb concentration: 8.9% (target 4–8%). Drink to thirst. Do not force-fluid past the per-hour target.

Field Notes

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