Estimates daily required water intake and insensible (evaporative) water loss for adults, based on body weight and body temperature.
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Calculation basis and official references
Reviewed on:
This calculator is not a diagnosis, treatment plan, or prescription. Please consult a qualified clinician about your medical decisions. This calculation applies to adults only.
Formula basis
Required water intake (mL/day) = weight(kg) × 40. Insensible water loss (mL/day) = weight(kg) × 15 + 200 × (temperature(°C) − 36.8). This implementation does not cut off the calculation anywhere within the allowed input range (weight 1-400 kg, temperature 35-42°C).
Calculation method
A simplified adult formula estimating daily required water intake from body weight, and estimating insensible (evaporative) water loss from body weight and body temperature.
Exclusions and checks required
The required-intake coefficient (30-40 mL/kg/day) is a widely used clinical nutrition rule of thumb; it does not account for dehydration, fever, heart failure, kidney failure, or age.
The insensible-loss formula is widely cited in clinical practice as coming from a nutrition support textbook, but this review could only confirm the publisher's bibliographic listing, not the formula text itself as printed in the book.
The validity of applying this simplified formula outside a normal body-temperature range (roughly 35.0-37.5°C) has not been confirmed.
Not applicable to people with serious illness or to infants; follow the guidance of a healthcare professional.
Example input:：Example for weight 65 kg and temperature 36.8°C
weight
65
temp
36.8
This is a simplified estimate that assumes a normal body temperature; actual water needs vary substantially with health condition and activity level.
一般社団法人日本静脈経腸栄養学会 静脈経腸栄養テキストブックNankodo (edited by the Japanese Society for Parenteral and Enteral Nutrition, now the Japanese Society for Clinical Nutrition and Metabolism)
Who is this calculator for? Required Water Intake and Insensible Water Loss
Estimates daily required water intake and insensible (evaporative) water loss for adults, based on body weight and body temperature.
What values should I enter?
Applies to: Body & metabolism
How should I interpret this estimate?
A simplified adult formula estimating daily required water intake from body weight, and estimating insensible (evaporative) water loss from body weight and body temperature.
How to use
Enter your input values and press Calculate.
Review the result and compare it with expected context.
Required water intake (mL/day) = weight(kg) × 40. Insensible water loss (mL/day) = weight(kg) × 15 + 200 × (temperature(°C) − 36.8). This implementation does not cut off the calculation anywhere within the allowed input range (weight 1-400 kg, temperature 35-42°C).