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ORS / Rehydration Calculator

Weight-based oral and IV rehydration for paediatric diarrhoea. WHO Plan A, B and C with country-specific guidance for Nigeria, Kenya and Ghana.

🇳🇬 Nigeria 🇰🇪 Kenya 🇬🇭 Ghana WHO 2023 📶 Offline-capable Under-5 · Diarrhoea #2 killer

Clinical tool — for use by qualified healthcare professionals only. Doses are calculated from WHO guidelines (2023), BNF for Children 2024, and national MOH protocols for Nigeria, Kenya and Ghana. Always apply clinical judgement. Values verified by a credentialed clinician reviewer — see About page. Report an error ↗

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Clinically reviewed by

Dr. Emeka Eze, FWACP (Paeds)

Paediatric Emergency Physician, Lagos University Teaching Hospital

Updated
2025-09-01

Step 1 — Select Country Protocol

Step 2 — Patient Details

Weight (kg) *

Age

yrs

Patient Group

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— ml ORS

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Rate

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Duration

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Zinc supplement

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Zinc Supplementation

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Feeding Guidance

Continue feeds

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ORS Preparation

1 sachet

Dissolve in 1 litre of clean water. Do not add sugar or salt. Use within 24 h.

Antibiotic Therapy

Not routinely indicated

ORS is the primary treatment for most acute watery diarrhoea.

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Reassessment Checklist

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Quick Reference — ORS Volume by Weight

Weight	Age (approx.)	Plan A (24 h)	Plan B (4 h)	Zinc dose

⚑ Flag a dosing concern or error

About This Calculator

Diarrhoeal disease remains the second leading cause of childhood mortality globally and a leading cause of hospitalisation in sub-Saharan Africa. Oral rehydration therapy (ORT) — the correct ORS volume prescribed based on WHO clinical dehydration assessment — is the single most cost-effective intervention in child health, estimated to have saved over 50 million lives since its introduction. This tool implements WHO IMCI dehydration classification and the three-plan rehydration protocol (Plan A: no dehydration, Plan B: some dehydration, Plan C: severe dehydration) adapted with Nigerian and Kenyan clinical context including available ORS formulations and IV fluid alternatives.

References & Guidelines

WHO/UNICEF: Clinical Management of Acute Diarrhoea (2004)
WHO IMCI: Management of Diarrhoea — Plans A, B and C
FMOH Nigeria IMCI Guidelines — Diarrhoea management chapter
Kenya MOH: Clinical Guidelines for Management and Referral (2016)

Frequently Asked Questions

What is the difference between WHO Plan A, B and C rehydration? ▾

What are the signs of severe dehydration in a child? ▾

Is zinc given with ORS for childhood diarrhoea? ▾

How is ORS prepared correctly when sachets are unavailable? ▾

What is the ReSoMal formula and when is it used instead of standard ORS? ▾

Related calculators

For children with severe dehydration requiring IV fluid resuscitation (WHO Plan C), see the Paediatric IV Fluid Calculator.
For zinc supplementation and antibiotic dosing alongside ORS therapy, use the Paediatric Drug Dose Calculator.

📋 Guideline basis: WHO/UNICEF IMCI 2004 · FMOH Nigeria · Last reviewed: January 2025 · Next review due: January 2026 · Disclaimer · Report an error