Allowable Blood Loss (ABL) Calculator

Allowable Blood Loss (ABL) Calculator

Allowable Blood Loss Calculator

Estimates blood volume and allowable blood loss from weight and selected haemoglobin or hematocrit targets. Educational planning tool only.

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Medical Wizardry • Calculators Sharp UI • Responsive

Inputs

EBV uses typical teaching values (millilitres per kilogram) by age group and sex. ABL is an estimate to support planning and must be interpreted with clinical context and local transfusion policy.

Results

—
Estimated blood volume
(millilitres)
—
Allowable blood loss
(millilitres)
Enter values
Formula used: Allowable blood loss = Estimated blood volume × (Start − Target) ÷ Start
This proportional method is commonly taught using hematocrit; haemoglobin can be used similarly for estimation.
References (for the concept):
  • Allowable blood loss / maximum allowable blood loss formula is a standard anaesthesia teaching method (Estimated blood volume × proportional drop from baseline).
  • Restrictive transfusion strategies commonly use haemoglobin thresholds around 7 to 8 grams per decilitre in stable adults, with higher thresholds in selected contexts; apply institutional patient blood management policy.
  • Estimated blood volume “millilitres per kilogram” tables vary slightly across sources; this tool uses typical teaching values.
Disclaimer: Educational tool. Not a substitute for clinician judgement or local protocol.
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