Here you can find an example of what you are looking for.
Hemorrhagic shock is a condition of reduced tissue perfusion, resulting in inadequate blood oxygen and nutrients levels that are necessary for cellular function. Whenever cellular oxygen demand outweighs supply, both the cell and the organism are in a state of shock.
A hemorrhagic shock classification uses a patients body weight to determine the total volume of blood.
E.g. 7% of the a 70 Kg person is 4.9 kilograms. That can be converted to 4.9 liters of blood.
Next there are 4 stages of classification:
Class 1 - 15% of total blood volume - 750 mL Blood lost-
Class 2 - 15-30% of total blood volume - 50 mL to 1500 mL Blood lost-
Class 3 - 30-40% of total blood volume - 1500 mL to 2000 mL Blood lost-
Class 4 - >40% of total blood volume - no assigned value -
Attached here is a shock calculator that uses Systolic BP and Heart Rate/Pulse.
A similar one can be found here.
Alternatively some blood loss calculations during birth may help.
These are some calculations:
- Calculated pregnancy blood volume = (0.75 ([maternal height (inches) X 50]+ [maternal weight in pounds X 25])
- Percent of blood volume lost = (Predelivery HCT- postdelivery HCT) / predelivery HCT.
- Calculated estimated blood loss (cEBL) = Calculated pregnancy blood volume X Percent of blood volume lost
More information can be found here.
More accurate calulcations
If you were seeking to calculating the True Volume of Blood Loss, the calculations present in this (no-pay wall) PDF may provide greater insight to you.