Free tool · educational, in a real emergency call 108

Blood loss calculator.

Enter a body weight and an estimated blood loss to see it as a percentage of total blood volume, the number medical teams use to grade severity.

Body weight (kg)

Estimated blood loss (mL)

A blood donation bag is 450 mL, compare with that.

This is an educational estimate, never a diagnosis.Active bleeding is a 108-emergency. Do not use this tool to decide whether to seek care, use it to understand scale, and call for help regardless.

The four severity classes (standard trauma teaching)

Class I, under 15%

Like a blood donation. Body compensates fully; pulse and BP barely move.

Class II, 15-30%

Fast pulse, anxiety. Needs medical assessment, this is hospital territory.

Class III, 30-40%

Confusion, low BP, weak pulse. This is a transfusion-and-resuscitation emergency.

Class IV, over 40%

Life-threatening. Immediate intensive care. Nothing at home applies here.

Why weight matters: blood volume scales with body size (~70 mL/kg), so the same 500 mL is 10% of one person and 7% of another. Volume calculator here. Assam's trauma and maternity units depend on voluntary donors for Class III-IV situations, be on the register before your district needs you.

How the severity bands work

The classes above follow standard ATLS trauma teaching: under 15% loss usually means few visible signs; 15,30% adds a racing heart; 30,40% drops blood pressure; over 40% is life-threatening. The maths: estimated blood volume × the percentage you enter.

The only rule that matters

Real bleeding is a 108/ambulance problem, not a calculator problem. Use this tool to understand what doctors mean by "Class II shock", never to decide care. Call emergency services first, always.