Maximum Allowable Blood Loss (ABL)
Maximum allowable blood loss (Gross 1983): estimated blood volume (weight × category factor) times (initial − target hematocrit) / initial; an intraoperative transfusion-planning estimate.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Patient category
- Adult male (75 mL/kg)
- Weight
- 70 kg
- Initial hematocrit (%) or hemoglobin
- 42
- Target (minimum acceptable) hematocrit or hemoglobin
- 30
Result: ABL 1500 mL — maximum allowable blood loss before reaching the target hematocrit.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Use
- An intraoperative transfusion-planning estimate of the blood loss tolerated before reaching the target hematocrit — not a transfusion order. Hematocrit or hemoglobin, same measure for both.
What you enter
- Patient category (blood-volume factor)
- Weight
- Initial hematocrit (%) or hemoglobin (g/dL)
- Target (minimum acceptable) hematocrit or hemoglobin (same measure)
How this is calculated
- Formula
- ABL = EBV × (Hct initial − Hct target) / Hct initial, EBV being the estimated blood volume. The average-hematocrit form divides by the mean of the two instead.
Gross JB. Estimating allowable blood loss: corrected for dilution. Anesthesiology. 1983;58(3):277-280. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.