How this calculator works
This implements the 2016 British Society for Haematology top-up formula for a non-bleeding infant or child. It uses the desired haemoglobin rise, body weight and an explicit factor of 3 to 5; the guideline considers 4 reasonable to reduce over-transfusion. It is not an exchange-transfusion, active-haemorrhage or haemoglobinopathy protocol. Donor haematocrit and the clinical situation affect the actual response, so a precise haemoglobin rise cannot be guaranteed. The guideline asks clinicians to double-check top-up volumes above 20 mL/kg and to respect an appropriate adult-volume maximum. The result is an estimate for information only and is not medical advice.
Formula
Volume(mL) = desired Hb increase(g/L) × weight(kg) × factor/10. Expected increase(g/L) = 10 × volume/(weight × factor). This page does not convert donor haematocrit into an unverified factor.
Worked example
A 10 kg child, a planned rise of 20 g/L and factor 4 give 80 mL, or 8 mL/kg. A 5 kg child with a 30 g/L rise and factor 4 gives 60 mL, or 12 mL/kg.
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Frequently asked questions
Does this decide whether to transfuse?
No. It only rearranges a published top-up arithmetic method. The indication, compatibility and administration plan require the treating team.
Can I enter donor haematocrit as the factor?
No. The factor is a coefficient from the BSH method, not a haematocrit fraction or percentage.
Why is there a warning above 20 mL/kg?
The 2016 guideline explicitly recommends double-checking top-up volumes above that amount. This page does not cap or approve a prescription.