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Blood Volume Calculator

Estimates total blood volume from sex, height and weight with the Nadler (1962) equation, or from weight and body build with Gilcher's rule of fives (mL/kg), and splits it into plasma and red cell volume when the haematocrit is given.

When to use

You need an adult's estimated total blood volume (L, mL or mL/kg) or plasma volume, for example to express blood loss as a fraction of volume or to plan apheresis or plasma exchange.

Do not use when: The person is a child or neonate (paediatric mL/kg norms differ), pregnant, or has extreme body composition; measured (isotope-dilution) volumes are needed for dosing decisions. Results are informational and not medical advice.

Formula

Nadler: BV (L) = 0.3669 × h³ + 0.03219 × weight_kg + 0.6041 (male) or 0.3561 × h³ + 0.03308 × weight_kg + 0.1833 (female), h = height_cm / 100 in metres. Gilcher: BV (mL) = weight_kg × factor, factor (mL/kg) male athletic 75 / normal 70 / thin 65 / obese 60, female 70 / 65 / 60 / 55. plasma_volume_ml = BV × (1 − hematocrit_percent / 100); red_cell_volume_ml = BV × hematocrit_percent / 100

Nadler's regression was fitted to isotope-dilution measurements in healthy adults and is the equation built into apheresis instruments; Gilcher's rule is a bedside approximation. Both assume normal hydration and typically differ by up to about 10%. Results are informational only and not a substitute for clinical judgement or medical advice.

Inputs

Parameter	Type	Unit	Required	Description
`sex`	enum: male \| female		yes	Sex used to select the formula coefficients or thresholds.
`height_cm`	number	cm	yes	Height in centimetres (used by the Nadler equation). Range: ≥ 100, ≤ 250
`weight_kg`	number	kg	yes	Body weight in kilograms. Range: ≥ 20, ≤ 400
`method`	enum: nadler \| gilcher_rule		default nadler	Estimation method; Gilcher's rule uses weight and build only.
`build`	enum: athletic \| normal \| thin \| obese		default normal	Body build used only by Gilcher's rule; ignored by Nadler.
`hematocrit_percent`	number	%	no	Optional haematocrit in percent; enables plasma and red cell volume. Range: ≥ 10, ≤ 70

Outputs

Output	Type	Unit	Description
`blood_volume_l`	number	L	Estimated total blood volume in litres.
`blood_volume_ml`	number	mL	Same volume in millilitres.
`ml_per_kg`	number	mL/kg	blood_volume_ml / weight_kg (adult norms about 60–75 mL/kg).
`plasma_volume_ml`	number	mL	Blood volume × (1 − haematocrit); only when hematocrit_percent is given.
`red_cell_volume_ml`	number	mL	Blood volume × haematocrit; only when hematocrit_percent is given.
`method_used`	string		Equation or factor applied.

Example

Male, 180 cm, 80 kg, haematocrit 45% (Nadler): {"sex":"male","height_cm":180,"weight_kg":80,"hematocrit_percent":45} → {"blood_volume_l":5.319,"blood_volume_ml":5319,"ml_per_kg":66.5,"plasma_volume_ml":2925,"red_cell_volume_ml":2394}

Female, 165 cm, 60 kg (Nadler): {"sex":"female","height_cm":165,"weight_kg":60,"method":"nadler"} → {"blood_volume_l":3.768,"blood_volume_ml":3768,"ml_per_kg":62.8}

GET https://tttkmbb.com/api/v1/calculate/blood-volume?sex=male&height_cm=180&weight_kg=80&hematocrit_percent=45

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/blood-volume (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/blood-volume · Markdown: https://tttkmbb.com/medical/blood-volume.md · JSON definition: https://tttkmbb.com/medical/blood-volume.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="blood-volume"
OpenAPI operationId: estimate_blood_volume
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

FAQ

Which method should I use?

Nadler when height is known: it is the standard regression and what apheresis systems use. Gilcher's rule needs only weight and a build category and is a rounder estimate.

Why is mL/kg lower in obesity?

Adipose tissue is poorly vascularised, so blood volume rises more slowly than weight; Nadler captures this through the height term and Gilcher through the obese factor (60 / 55 mL/kg).

How is this used for blood loss?

Haemorrhage classes are fractions of total volume: 15% of a 5.3 L volume is about 800 mL. The estimate does not account for pregnancy, dehydration or anaemia.

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