Work out dehydration percentage instantly with clear inputs, formula shown and shareable results.
Compares current weight with a known pre-illness weight; each kilogram lost represents about one litre of fluid deficit.
Dehydration from weight change
Dehydration (%) = (pre-illness weight - current weight) / pre-illness weight x 100; deficit (mL) = weight lost (kg) x 1000
Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
Clinical signs are used instead, which are less precise; weight change remains the reference standard.
Usually over 24 to 48 hours alongside maintenance fluids, faster only in shock.