CBC Differential Calculator

A standard CBC differential reports each white blood cell type as a percentage of the total count, but percentages alone can be misleading -- a "normal" 60% neutrophil reading means something very different in a patient with a WBC of 3.0 versus 18.0. This calculator converts each percentage into an absolute count in the same x10^3/uL units as total WBC, using Absolute Count = WBC x Percentage / 100 for each cell type. The Absolute Neutrophil Count (ANC) -- the field most often used clinically to gauge infection risk -- uses the standard formula ANC = WBC x (Segmented Neutrophils% + Bands%) / 100, including band forms (immature neutrophils) alongside mature segmented neutrophils, since a bandemia (a rise in band forms without a change in segmented neutrophils, as seen in sepsis and other acute infections) still raises true ANC even though it would be missed entirely by a segs-only formula. Because that formula multiplies WBC by each cell type's own percentage, raising a percentage input raises that cell type's absolute count directly and proportionally -- there is no interaction or offset between the cell types' calculations: Eosinophil percentage, for instance, has no effect whatsoever on Absolute Neutrophils.

The neutrophil-to-lymphocyte ratio (NLR), a marker increasingly used as a general indicator of systemic inflammation, is calculated by dividing absolute neutrophils by absolute lymphocytes -- except when absolute lymphocytes is exactly 0, which makes the ratio mathematically undefined rather than 0; this calculator reports that case as a flagged "Critical -- undefined" state instead of silently showing 0, since a near-absent lymphocyte count is itself an alarming result that a 0 ratio would falsely mask. Because the six percentage inputs (including Bands) are entered independently rather than derived from each other, this calculator also totals them and warns when they don't sum to approximately 100% of the WBC -- a differential that doesn't reconcile means the absolute counts below it won't reconcile with total WBC either. Abnormal Flags counts how many of the panel's parameters fall outside typical reference ranges, giving a quick summary of how many values need a closer look rather than a single overall verdict.