Skip to content
ENExplore Calculators

Blood Loss Estimate Calculator

Work out blood loss estimate instantly with clear inputs, formula shown and shareable results.

About Blood Loss Estimate Calculator

Estimates blood loss from the fall in haematocrit relative to the patient's estimated blood volume.

Formula

Blood loss from haematocrit

EBV = weight x mL/kg; loss = EBV x (starting Hct - current Hct) / starting Hct

Worked example

With the default values below, Blood Loss Estimate Calculator returns Estimated blood loss of 1,225. Change any input above and every figure here is recalculated in your browser.

Inputs used

Body weightaccepts 2–250 kg
70 kg
Starting haematocritaccepts 15–60 %
40 %
Current haematocritaccepts 10–60 %
30 %
Blood volume per kilogramaccepts 50–100 mL/kg
70 mL/kg

Results

Estimated blood loss
1,225 mL
Estimated blood volume
4,900 mL
Share of blood volume lost
25.0%

Step by step

  1. 1Values used
  2. 2Blood loss from haematocrit
  3. 3Estimated blood loss= 1,225 mL
  4. 4Estimated blood volume= 4,900 mL
  5. 5Share of blood volume lost= 25.0

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 1 decimal place, 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.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

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

Why can this underestimate acute loss?

Haematocrit falls only after fluid shifts or resuscitation dilute the remaining blood, which lags behind rapid bleeding.

What blood volume factor applies?

About 70 mL/kg in adult men, 65 in women, 80 in infants and 85 to 90 in neonates.

Related Calculators

Blood Loss Estimate Calculator | Calcrivo