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Oral Rehydration Solution Calculator

Work out oral rehydration solution instantly with clear inputs, formula shown and shareable results.

About Oral Rehydration Solution Calculator

Compares the weight-based fluid deficit with the WHO Plan B figure of 75 mL/kg over four hours and uses the larger volume.

Formula

WHO Plan B

ORS volume = 75 mL/kg over 4 hours for some dehydration; deficit (mL) = weight (kg) x 1000 x dehydration fraction

Worked example

With the default values below, Oral Rehydration Solution Calculator returns Oral rehydration solution required of 900. Change any input above and every figure here is recalculated in your browser.

Inputs used

Body weightaccepts 2–80 kg
12 kg
Estimated dehydrationaccepts 0–12 %
5 %
Rehydration periodaccepts 1–24 h
4 h

Results

Oral rehydration solution required
900 mL
Rate over the period
225 mL/h
Calculated deficit
600 mL
One-litre sachets required
0.90

Step by step

  1. 1Values used
  2. 2WHO Plan B
  3. 3Oral rehydration solution required= 900 mL
  4. 4Rate over the period= 225 mL/h
  5. 5Calculated deficit= 600 mL
  6. 6One-litre sachets required= 0.90

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or fees or charges into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

What is in low-osmolarity ORS?

Per litre: 2.6 g sodium chloride, 13.5 g glucose, 1.5 g potassium chloride and 2.9 g trisodium citrate.

When is ORS not appropriate?

In shock, persistent vomiting, ileus or altered consciousness, where intravenous rehydration is needed.

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