B Cell Count Calculator

Calculator Inputs

Reset

Enter values from your CBC and flow cytometry report. Fields switch automatically based on your calculation mode.

Calculation mode

Pick the pathway that matches your lab data.

WBC

If your report shows 6.5 x10³/µL, enter 6.5 and select x10³/µL.

Lymphocytes (% of WBC)

%

Used to estimate absolute lymphocyte count.

Absolute lymphocyte count (ALC)

Use when your CBC already reports ALC.

B cells (% of lymphocytes)

%

Often reported as CD19+ or CD20+ percentage.

Sample volume (optional)

mL

If provided, the calculator estimates total cells in the sample.

Label (optional)

Saved into your export files.

Notes (optional)

Formula Used

This calculator estimates the absolute B cell count using standard percentage-to-absolute conversions.

ALC (cells/µL) = WBC (cells/µL) × Lymph% / 100
B cells (cells/µL) = ALC (cells/µL) × B% / 100
cells/mL = cells/µL × 1000 and cells/L = cells/µL × 1,000,000
If sample volume is provided: Total cells = cells/mL × volume(mL)

How to Use This Calculator

Select a calculation mode that matches your lab report.
Enter WBC and lymphocyte percent, or enter ALC directly.
Add B cell percent from flow cytometry (often CD19+).
Press Calculate to view results above the form.
Use Download CSV or Download PDF to export.

Example Data Table

Example values show how the calculator converts common lab units and percentages.

Scenario	Mode	WBC	Lymph%	ALC	B%	Absolute B cells (cells/µL)
Typical adult example	WBC pathway	6.5 x10³/µL	30%	1,950 cells/µL	12%	234 cells/µL
Direct ALC entry	ALC pathway	—	—	1,800 cells/µL	8%	144 cells/µL
High B% example	WBC pathway	9,200 cells/µL	35%	3,220 cells/µL	20%	644 cells/µL

Examples are for demonstration only. Use lab-validated reference ranges and clinical context for interpretation.

What B Cell Count Represents

B cells are lymphocytes that mature in bone marrow and support antibody production. Flow cytometry commonly reports CD19+ or CD20+ cells as a percent of lymphocytes. This calculator converts that percentage into an absolute concentration, which is often reported as cells per microliter in clinical labs, and can be trended across visits. Because WBC and lymphocyte fractions fluctuate, absolute counts usually track immune recovery more reliably than percentages alone.

Inputs That Drive Absolute Counts

Absolute B cells depend on the absolute lymphocyte count (ALC). If ALC is not listed, it can be estimated from a complete blood count using WBC and lymphocyte percent. For example, a WBC of 6.5×10³/µL and lymphocytes of 30% yields an ALC near 1,950 cells/µL; with B cells at 12%, the absolute B cell count is about 234 cells/µL.

Unit Conversion and Consistency Checks

Laboratory reports may use cells/µL or ×10³/µL. The tool normalizes both by converting ×10³/µL to cells/µL, then applies percentage multipliers. It also provides cells/mL and cells/L using fixed factors: 1,000 µL per mL and 1,000,000 µL per L. Entering a sample volume enables an estimated total cell count in that tube. Use reasonable significant figures; extreme rounding can hide clinically meaningful changes over time.

Interpreting Results in Context

Reference intervals vary by age, method, and clinical condition, so interpretation should use your lab’s ranges. Many adult reports show roughly 100–500 B cells/µL, while lower values can occur after anti‑CD20 therapy or in some immunodeficiencies. Higher values may appear with reactive lymphocytosis or certain lymphoproliferative disorders, but diagnosis requires full immunophenotyping and clinical review. Always document the gating strategy and marker used, since CD19 and CD20 can differ after targeted therapy.

Reporting and Exporting for Follow‑Up

Clean documentation helps longitudinal monitoring. The CSV export stores inputs, calculated ALC, and absolute B cell outputs for spreadsheets or EHR notes. The PDF report is useful for attaching to emails or lab packets during clinic follow‑up. When comparing time points, keep units consistent and record whether the percentage is gated on lymphocytes or total leukocytes. Add a clear label and notes to preserve context, such as treatment day or symptom status.

FAQs

Which lab values do I need to calculate absolute B cells?

You need B cell percent from flow cytometry plus either absolute lymphocyte count (ALC) or WBC and lymphocyte percent from the CBC differential. Optional sample volume estimates total cells in the collected specimen.

What if my report uses ×10³/µL units?

Enter the numeric value and select the ×10³/µL unit option. The calculator converts to cells/µL internally, then applies the percentage formulas to produce cells/µL, cells/mL, and cells/L.

Does B cell percent have to be gated on lymphocytes?

Ideally, yes. Many reports present B% as a fraction of lymphocytes after gating. If your report uses total leukocytes or a different gate, the absolute result will not match; use the same denominator as your ALC pathway.

Can I use CD19+ or CD20+ percentages?

Yes, if the percent represents the B cell population you want to track. CD19 and CD20 can diverge after targeted therapy, so document which marker was used and keep it consistent across time points for comparisons.

Why can absolute B cells change even if B% stays similar?

Absolute counts depend on ALC. If WBC or lymphocyte percent shifts, ALC changes, and the same B% produces a different absolute count. This is why absolute values are commonly used for monitoring treatment response.

Is this calculator appropriate for diagnosis?

No. It is a computation aid for converting reported percentages into absolute counts. Clinical decisions should use your laboratory reference ranges, full immunophenotyping, and a clinician’s interpretation of symptoms, medications, and underlying conditions.