Small children have small blood volumes, so what seems like a minor blood loss or a series of blood tests can be significant. A 3 kg newborn has only about 255 mL of blood.
How to use the Pediatric Blood Volume Calculator
- Age group
- Weight
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose the age group and enter weight.
Inputs explained
| Field | What to enter |
|---|---|
| Age group | Choose one: Preterm newborn (100 mL/kg), Term newborn (85 mL/kg), Infant 1–12 months (78 mL/kg), Child (75 mL/kg) … |
| Weight | Units: kg, lb, st, g |
What each result means
- Estimated blood volume = [Age group]×[Weight]
- 10% of blood volume = [Estimated blood volume]×0.1
- 25% of blood volume (significant loss) = [Estimated blood volume]×0.25
Example values
How the main result changes when Weight changes and everything else stays at the example values above:
| Weight (kg) | Estimated blood volume (mL) |
|---|---|
| 10 | 750 |
| 15 | 1,125 |
| 20 | 1,500 |
| 25 | 1,875 |
| 30 | 2,250 |
| 40 | 3,000 |
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.
Formula
Blood volume = weight × mL/kg
Preterm 90–105 · term newborn 85 · infant (1–12 months) 75–80 · child 70–75 · adolescent and adult 65–70 mL/kg
Worked example
Inputs — Age group: Child (75 mL/kg); Weight: 20 kg.
Results — Estimated blood volume = 1,500 mL; 10% of blood volume = 150 mL; 25% of blood volume (significant loss) = 375 mL.
Key terms
- EBV
- Estimated blood volume.
Frequently asked questions
How much blood does a newborn have?
About 85 mL/kg – roughly 300 mL for a 3.5 kg baby.
How much blood loss is dangerous in a child?
Losing 25% or more of blood volume can cause shock.
Why is the volume per kg higher in babies?
Their bodies have proportionally more blood relative to weight.