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
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
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
Q. How 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.
Q. Can you walk through an example?
With Weight (kg) 60, Dose (mg/kg) 70, the answer is Blood volume 4,200mL.
Q. What do I need to enter?
Enter Weight (kg), Dose (mg/kg). The result recalculates as you type, and an empty box counts as zero.
Q. How 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.
Q. How 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.
Q. Anything to watch out for?
Donations are kept within roughly 10% of blood volume, which is why whole-blood donation has a minimum weight.
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These calculators help you understand health figures; they do not replace diagnosis or prescription. See a clinician if you have symptoms.