Blood Donor Calculator

This blood donation calculator tool is based on the actual amount of blood in your body which forms the basis for all other blood donation data. It estimates total blood volume by gender, size and weight to show what it means when you donate blood.

They will tell you if you meet the weight requirements, how much blood can safely be drawn at one donation and how many times overall you can donate within a certain time period and how much blood you provide.

How much blood is there in your body?

The average amount of blood in an adult is about 4.5 to 6 liters, which makes up approximately 7 to 8 percent of body weight. The exact values depend not only on the weight but also on the stature, so height is used for a more accurate estimation.

This tool uses two methods commonly used by doctors. Select the method that works best for you and change the volume unit to milliliters, liters or fluid ounces if desired.

Method 1: Nadler's Equation

Nadler and his colleagues published this formula in 1962. It is used as a standard formula in hospitals when the height and weight are known. Different coefficients for men and women are used because of differences in body composition.

The height is given in meters and the weight in kilograms, and the result will be shown in liters. Note that the height is a cubic calculation, which means that blood volume increases faster for larger people.

So for a man who is 1.80 m tall and weighs 80 kg, his height cubed would be about 5.832. So if you multiply 0.3669 by 5.832, that's 2.140, then you multiply 0.03219 by 80, which is 2.575 and finally add 0.6041. The total volume would be about 5.32 liters or 5320 milliliters.

Method 2: The Lemmens-Bernstein-Brodsky.

At higher body weight the Nadler formula tends to overestimate the result. The Lemmens-Bernstein-Brodsky formula of 2006 solved this problem by correcting the classic value of 70 mL/kg using a body size index.

The higher the BMI, the lower the blood volume per body weight. For very thin people it is about 100 mL/kg while for severely obese nearly 43 mL/kg, reflecting this pattern in the formula. As no information on sex is used, it can also be useful when gender distinction is not required.

Are you eligible to donate blood? How often can you give it?

Most facilities require donors to be at least 110 pounds or about 50 kg. This is to reduce the strain on the body when a unit of blood is removed. The age limit is usually between 16 and 17 years, with consent required.

The amount of blood drawn is regulated by the authorities in charge of supervision depending on body weight. The US FDA sets an upper limit for blood draw, including samples, at about 10.5 mL per kilogram of body weight. As a guideline, a single donation should not be more than about 13 to 15 percent of total blood volume. Therefore, a standard unit of whole blood of 500 mL in an average adult would be about 8 to 10 percent, which is within the safe range. For those with low body weight, a smaller amount of 350 mL will be drawn.

Types and frequency of blood donation

The recovery time varies according to the type of blood donation, so there are specific intervals and annual maximums for each type.

The plasma recovers within one day while red blood cell regeneration takes about four to six weeks and iron stores recovery takes about six to eight weeks. The slow iron recovery is the main reason that whole blood donors must wait eight weeks between donations.

Long-term effects

As a whole blood donation is split into red cells, plasma and platelets, one single donation can potentially help up to three patients. If you donate regularly over many years these numbers add up quickly.

With a maximum of six donations per year and ten years of donating activity, there can be 60 total donations, which could help up to 180 patients and provide about 30 liters of blood. A calculator tool calculates these results based on the type of donation, volume per donation, and number of years.

What is blood made of?

Blood is mainly made up of plasma (about 55%) and red blood cells (about 45%), while white blood cells and platelets make up less than 1% together. The chart shows the estimated amount of each component in a sample of blood.

This tool is for educational and planning purposes only. It does not constitute medical advice, nor guarantee that certain donation requirements will be met. The formulas used to calculate blood volume are estimates, and it's important to have a health check before each donation. Please follow the instructions of your local blood service organization and qualified healthcare professionals.