Blood Volume Calculator
Our blood volume calculator uses three methods to determine the total blood volume. The first uses Dr. Nadler's formula; the second is an equation developed by Dr. Lemmens, Dr. Bernstein, and Dr. Brodsky. There's also a third method that gives a better perspective on the previous two.
Preoperative assessment of estimated blood volume (BV) is essential for patients undergoing surgery. It impacts perfusion care, including hemodynamic and pharmacologic interventions and transfusion practices (see our blood donor calculator). Keep on reading to understand how blood volume affects blood pressure.
Please note that this is a calculator of blood volume for adults. If you want to estimate the blood volume in a child, use our pediatric blood volume calculator.
We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. If any health condition bothers you, consult a physician.
How does this blood volume calculator work?
Blood volume comprises the liquid (plasma – learn more with our fresh/frozen plasma dose calculator) and cellular part. Several methods are available to directly or indirectly measure blood volume, but all are impractical in routine clinical practice.
The mean value for indexed blood volume (ᵢBV) in normal-weight adults is 70 mL/kg for males and 65 mL/kg for females. You can use weight to calculate the blood volume in the third method section.
Since ᵢBV decreases in a non-linear manner with increasing weight, this value can't be used for obese and morbidly obese patients. The methods of estimating total blood volume we provide here take into account the entire range of body weights.
Nadler's Equation for total blood volume – Method 1
An advanced formula used to calculate blood volume was developed by Dr. Allen in 1956.
In 1962, based on Dr. Allen's work, Dr. Nadler found more accurate coefficients and published the equation in his article titled Prediction of blood volume in normal human adults.
Our blood volume calculator uses this formula:
- For males:
- For females :
💡 We can use Nadler's formula to, for example, compute the proper immunoglobulin dose in pregnancy.
Lemmens-Bernstein-Brodsky equation for estimated blood volume - Method 2
In 2006, Dr. Lemmens, Dr. Bernstein, and Dr. Brodsky discovered an equation that allows physicians to predict ᵢBV over the full spectrum of body weights and body mass indices (BMI) in patients unstressed by acute trauma or critical illness.
The blood volume calculator uses this formula:
How does blood volume affect blood pressure?
Factors that affect blood pressure (BP) are interconnected:
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Peripheral resistance – the constriction of the arteries elevates the BP. Peripheral resistance also includes: vessel length, blood viscosity, and arterial stenosis;
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Total blood volume; and
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Cardiac output (discover more with our stoke volume calculator).
The dynamic balance between blood volume and blood pressure is regulated by the complex (RAAS) controlled by the kidneys. In normal conditions, it maintains blood pressure in the range of 90-140 mmHg (systolic BP) and 60-90 mmHg (diastolic BP).
How do I calculate blood volume?
To calculate blood volume, take the following steps:
- Determine your weight in kilograms; and
- Multiply your weight by the average blood volume of your demographic, expressed in mL/kg.
Your average blood volume is estimated as follows:
- 75 mL/kg for adult males; and
- 65 mL/kg for adult females.
What is the normal range of blood volume?
4,500 to 5,700 mL is the usual range of blood volume for an average adult. The average blood volume level is 5 liters or 1.3 gallons, but women tend to have lower blood volume than men.
How does pregnancy affect my blood volume?
Total blood volume increases from 20% to 100% during pregnancy — usually, it's around 45%. Blood volume increases due to your heart working harder to eject more blood with each beat. The extra blood allows the fetus to grow and develop healthily.
How do I increase my blood volume?
To increase your blood volume:
- Have regular cardio workouts;
- Get a blood transfusion;
- Get IV fluid therapy; and
- Take iron supplements.
If you believe you have low blood volume, consult your physician before taking any of these steps.