Dehydration Calculator — How Much ORS Do You Need?
For mild-to-moderate diarrhea-related dehydration, oral rehydration solution (ORS) corrects fluids as effectively as IV — but most people drink too little, too slowly. This calculator gives the WHO-recommended amount. For severe dehydration, skip this page and come in — you need IV fluids, not ORS.
How to Make ORS at Home (No Sachet?)
1 liter clean water + 6 level teaspoons sugar + ½ level teaspoon salt — stir until dissolved. Drink small sips constantly, don't chug. Add a pinch of potassium salt or a mashed banana if available for potassium.
ORS on the Trail
- Carry 3–5 ORS sachets in your trek kit — each makes 1L
- Sachets + purified water = faster recovery than plain water
- Don't mix with juice or soda — changes the electrolyte balance
- Start early — mild dehydration caught at 5% is easier than 10%
The Fluid Math
Dehydration at altitude is not just uncomfortable — it compounds altitude sickness, reduces performance, and creates the headache/fatigue that mimics or worsens AMS. The fluid needs are higher than at sea level; the dehydration that would take hours to develop happens faster in the thin, dry air. The calculator provides the number; the discipline is drinking it.
Hydration strategy
- 3–4 liters daily minimum — more in heat/exertion
- ORS for significant losses — the electrolytes matter
- Urine color as guide — pale yellow means hydrated
- Drink before thirsty — thirst lags at altitude
- Electrolytes with intake — water alone is not enough for heavy losses
What the Dehydration Compounds
The altitude headache, the fatigue, the nausea — dehydration produces or worsens all of them. The trekker who attributes symptoms to altitude when they are dehydrated treats the wrong problem. The fix is simple: drink more. The complication is that the symptoms overlap — the hydration that addresses both is the safe answer regardless of which is causing the symptom.
The Factors
Dehydration calculation factors: the body weight, the altitude (the increased insensible losses), the activity level (the exertion that increases the sweat), the temperature (the heat that increases the losses), and the altitude's physiological response (the diuresis).
The Practical Application
For the practical application — the calculator that provides the daily fluid target for the trekker's specific profile (the weight, the altitude, the activity). For the trek, the hydration target that is more precise than the general "drink more" advice.
The Clinical Context
Dehydration calculator context — the estimate that supplements, not replaces, the clinical assessment. The signs (the skin turgor, the mucous membrane, the urine output) that are more reliable than the calculator.
The Severe Dehydration
For the severe dehydration — the clinical signs that determine the severity (the capillary refill, the BP, the mental status) and the treatment that is determined by the severity.
The Context
Dehydration context — the activity level (the higher that increases), the altitude (the increased respiratory loss), the temperature (the hot that produces the sweat), and the humidity (the dry that increases the loss).
The Symptom
Dehydration symptoms — the thirst (the late indicator), the dark urine (the concentration that indicates), the headache, the fatigue. For the dehydration, the intake that is increased.
The ORS Cost
ORS cost — the ~$0.20-0.50/sachet (the cheap that is essential). For the diarrhea/heat dehydration, the affordable that is carried.
The Homemade
Homemade ORS — the free (the salt + the sugar + the water that is mixed). For the field, the recipe that is effective.
The ORS Cost
ORS sachet — the ~$0.50-1 (the packed that resolves the mild). For the dehydrated, the carried that is the cheap treatment.
The Severe Cost
Severe dehydration — the IV ~$40-120 (the clinic that treats). For the prevented, the hydration that avoids the visit.
The ORS Cost
ORS packet — the ~$0.50-1 (the carried that is the kit). For the dehydrated, the dissolved that is the cheap fix.
The IV
Severe dehydration — the IV ~$40-120 (the escalated that is the clinic). For the collapsed, the given that is the route.
How much water do I need trekking?
3–4 liters per day at altitude for most adults — more in heat, more with exertion, more if vomiting or diarrhea. The calculator adjusts for your weight, activity, and conditions. Dehydration is a primary AMS risk factor and a common cause of trekking fatigue and headache.
What are the signs of dehydration?
Dark urine (should be pale yellow), thirst, dry mouth, headache, dizziness, fatigue, and decreased urine output. In altitude environments, dehydration compounds the AMS symptoms — the headache that is altitude vs dehydration is hard to distinguish; treating dehydration addresses both.
How do I treat dehydration?
Oral rehydration salts (ORS) in water — the electrolyte solution rehydrates more effectively than plain water for significant losses. For mild dehydration, water suffices; for diarrhea/vomiting or significant loss, ORS is the treatment. Drink steadily, not all at once.
Can I drink too much water?
Yes — hyponatremia (water intoxication) is real: excessive water dilutes sodium, causing confusion, seizures, and coma. The "drink constantly" advice has a limit — the electrolytes matter too. Drink to thirst plus a bit more; do not force liters beyond what the body can process.
How does altitude affect hydration needs?
Altitude increases fluid loss — the dry air, the increased breathing rate, and the diuresis (increased urination) all deplete fluids faster than at sea level. The hydration requirements are higher; the thirst that signals it lags behind. The trekker who does not consciously drink dehydrates.
