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Pediatric Blood Volume Calculator

Table of contents

Why is pediatric blood volume useful?How is the blood volume estimated in pediatrics?What's the blood volume in a newborn baby?What's the blood volume in infants and older children?FAQs

Our pediatric blood volume calculator uses body weight to find the total blood volume of children. The estimated blood volume in pediatrics depends on the age of the child. As such, there are separate formulas for blood volume in newborn babies, infants under three months of age, children over three months, and adolescents.

Interested? Keep reading to learn:

  • Why pediatric blood volume is useful;
  • How pediatric blood volume is estimated; and
  • The blood volume in infants.

Please note that we designed this pediatric blood volume calculator for children only. To estimate the blood volume in adults, check our blood volume calculator. You may also find this plasma volume calculator useful.

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace professional medical advice.

Why is pediatric blood volume useful?

Similar to the adult total blood volume, these values are vital in hospital perfusion care. This includes hemodynamic and pharmacologic interventions and transfusion practices.

Additionally, these values are critical in the process of blood collection for tests. For an adult patient, collecting 20 ml of blood won't have a noticeable impact on the organism, whereas the same amount of blood is about 8% of a newborn baby's total blood volume. According to the existing guidelines, the maximum volume of blood that can be drawn safely from an infant in 24 hours ranges from 1% to 5% of his total blood volume.

Are you interested in learning how much blood you can afford to lose before it is considered dangerously low? Visit our allowable blood loss calculator to learn more.

How is the blood volume estimated in pediatrics?

Our pediatric blood volume calculator uses the formula:

TBV = weight * age factor

The age factor equals:

  • 100 mL/kg for premature infants;
  • 85 mL/kg for babies younger than 3 months;
  • 75 mL/kg for children over the age of 3 months;
  • 70 mL/kg for male adolescents;
  • 65 mL/kg for female adolescents.

What's the blood volume in a newborn baby?

The volume of blood in a premature neonate ranges from 89 to 105 mL per kilogram of body weight, while a full-term baby has from 82 to 86 mL/kg of blood.

What's the blood volume in infants and older children?

The blood volume in infants and older children is markedly different.

  • The blood volume in infants up to three months of age is 82-86 mL/kg.
  • It is assumed that children have around 73-82 mL/kg of blood after the third month.
  • The volume of blood per kilogram of body weight decreases with age and in puberty reaches about the same values as in adults, which is 70 mL/kg for males and 65 mL/kg for females.

How much blood does a 7 month 16 lbs baby have?

7 months old, 16 lbs baby has approximately 544 ml of blood volume.

You can count it yourself, using the formula total blood volume = weight × age factor. Age factor is 75 mL/kg in our case.

How to calculate blood volume in pediatrics?

To calculate blood volume in pediatrics:

  1. You need to know the child's weight (in kilograms), and their age.
  2. Now, use the formula:
    TBV = weight × age factor,
    TBV - total blood volume;
    age factor - depends on the age:


Age factor [mL/kg]

Premature infant


Babies <3 months


Children >3 months


Male adolescents


Female adolescents


  1. That's it! You can always double-check with the pediatric blood volume calculator.

How much blood can be drawn from children at one time?

According to the Seattle Children's Hospital, you can draw a maximum 2.5% of the total blood volume in one draw.

For example, the limit for a single blood draw is ~16 mL per 8 kg (17.6 lbs) child and 62-70 mL for a child weighing 31-35 kg (68.3-77.2 lbs).

How much blood does a 13 year old have?

A 13-year-old has approximately 2925-3150 mL of blood volume.

Adolescents have approximately 70 mL/kg (males) or 65 mL/kg (females) of blood volume. As statistically, 13-year old weights about 100 lbs (~45 kg), the average blood volume for adolescents will be 3150 mL for males and 2925 mL for females.

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