# Plasma Volume Calculator

URL: https://speedycalculator.com/calculators/health/plasma-volume/
Last updated: 2026-10-30

> The plasma volume calculator estimates plasma volume from body weight and haematocrit with the Kaplan formula and from estimated blood volume, used for plasma exchange planning and fluid assessment.

## Inputs

- Sex
- Weight (kg, lb, st, g)
- Haematocrit (%)

## Results

- Plasma volume (Kaplan)
- Plasma volume (70 mL/kg)
- 1.25 plasma volumes (typical exchange)

## Formula

```
Kaplan: PV (mL) = (1 − Hct) × (b + c × weight kg); men b = 1530, c = 41; women b = 864, c = 47.9
Simple: PV = 70 mL/kg × weight × (1 − Hct)
```

## Explanation

Plasma is the liquid part of blood, about 55% of blood volume. Plasma volume estimates guide therapeutic plasma exchange (usually 1–1.5 plasma volumes per session).

### How to use the Plasma Volume Calculator

- **Sex**
- **Weight**
- **Haematocrit**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter sex, weight and haematocrit.

### Inputs explained

FieldWhat to enterSexChoose one: Male, FemaleWeightUnits: kg, lb, st, gHaematocritIn %

### What each result means

- **Plasma volume (70 mL/kg)** = 70×[Weight]×(1 - [Haematocrit]÷100)
- **1.25 plasma volumes (typical exchange)** = [Plasma volume (Kaplan)]×1.25

### Example values

How the main result changes when **Weight** changes and everything else stays at the example values above:

Weight (kg)Plasma volume (Kaplan) (mL)37.51,77956.252,225752,67193.753,117112.53,5631504,454
*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — Sex: Male; Weight: 75 kg; Haematocrit: 42 %.

Results — **Plasma volume (Kaplan) = 2,671 mL**; Plasma volume (70 mL/kg) = 3,045 mL; 1.25 plasma volumes (typical exchange) = 3,339 mL.

## Key terms

- **Plasma exchange**: Removing plasma and replacing it with albumin or donor plasma.

## FAQ

**What is a normal plasma volume?**
About 40–50 mL per kg, roughly 2.5–3.5 litres in adults.

**How much plasma is exchanged in plasmapheresis?**
Usually 1–1.5 plasma volumes per session.

**Why does haematocrit matter?**
The higher the haematocrit, the smaller the plasma share of blood.


## Sources

- [Kaplan AA. A simple and accurate method for prescribing plasma exchange. ASAIO Trans, 1990](https://pubmed.ncbi.nlm.nih.gov/2252707/)