Blood Volume Calculator

Adults hold about 70 mL per kilogram; newborns 85–90 mL. The second figure shows what share of your volume a 400 mL donation represents.

Your numbers

Weight (kg)Dose (mg/kg)

Blood volume

4,200mL

Result

9.5%

Formula

Blood volume = Weight (kg) × Dose (mg/kg)

Donations are kept within roughly 10% of blood volume, which is why whole-blood donation has a minimum weight.

What to enter

Input	Default	Accepted range
Weight (kg)The second weight you are comparing against.	60	1 ~ 200
Dose (mg/kg)How much drug is given per kilogram of body weight.	70	50 ~ 100

Step by step

FormulaBlood volume = Weight (kg) × Dose (mg/kg)

With the default numbersBlood volume = 60 × 70

AnswerBlood volume = 4,200 mL

Quick reference table

Results when only Weight (kg) changes and everything else stays put.

Weight (kg)	Blood volume (mL)	Result (%)
30	2,100	19
45	3,150	12.7
60	4,200	9.5
90	6,300	6.3
120	8,400	4.8

What each result means

Result	At default values
Blood volume (mL)Total blood in the body, estimated from weight.	4,200
Result (%)What the formula gives back — the answer this page is for.	9.5

Common mistakes

Donations are kept within roughly 10% of blood volume, which is why whole-blood donation has a minimum weight.

Glossary

Weight (kg): The second weight you are comparing against.
Dose (mg/kg): How much drug is given per kilogram of body weight.
Blood volume: Total blood in the body, estimated from weight.
Result: What the formula gives back — the answer this page is for.

Frequently asked questions

QHow is Blood Volume Calculator calculated?

Blood volume = Weight (kg) × Dose (mg/kg) — Adults hold about 70 mL per kilogram; newborns 85–90 mL. The second figure shows what share of your volume a 400 mL donation represents.

QCan you walk through an example?

With Weight (kg) 60, Dose (mg/kg) 70, the answer is Blood volume 4,200mL.

QWhat do I need to enter?

Enter Weight (kg), Dose (mg/kg). The result recalculates as you type, and an empty box counts as zero.

QHow much does the answer move if I change a number?

Changing only Weight (kg) moves the answer to Weight (kg) 30 → Blood volume (mL) 2,100 and Weight (kg) 120 → Blood volume (mL) 8,400. The table below lays out five steps.

QHow are the numbers rounded?

Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.

QAnything to watch out for?

Donations are kept within roughly 10% of blood volume, which is why whole-blood donation has a minimum weight.

Related calculators

Child's Predicted HeightEstimate a child’s adult height from the parents’ heights.Newborn Feeding AmountGet daily formula volume and per-feed amount from a baby’s weight.Newborn Weight GainCompare current weight against birth weight as a percentage.Paediatric Dose by WeightCompute a single dose and daily total from a mg/kg figure.

These calculators help you understand health figures; they do not replace diagnosis or prescription. See a clinician if you have symptoms.