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RDW-CV Unit Converter
Red Blood Cell Distribution Width (RDW) is a measure of the variation in red blood cell volume (anisocytosis). It is a standard component of a Complete Blood Count (CBC).
There are two ways to report RDW: RDW-CV (Coefficient of Variation) and RDW-SD (Standard Deviation). RDW-CV is a calculated percentage that depends on the Mean Corpuscular Volume (MCV), while RDW-SD is a direct measurement in femtoliters (fL). This tool converts between the two formats using the MCV.
RDW-CV (%)
PercentageCoefficient of Variation (Most common in US).
RDW-SD (fL)
Standard Deviation (Direct measure of width).
Clinical Context
Reference Ranges:
• RDW-CV: 11.5% – 14.5% (varies by lab).
• RDW-SD: 39 – 46 fL.
Interpretation: High RDW (Anisocytosis) is often the first sign of nutritional anemias (Iron, B12, Folate deficiency) before other indices change. It is also a strong prognostic marker in heart failure and sepsis.
Conversion Formula:
RDW-CV (%) = (RDW-SD / MCV) × 100.
RDW-SD (fL) = (RDW-CV × MCV) / 100.
Clinical References
How to Use This Converter
Follow these steps to convert between RDW-CV and RDW-SD.
Set MCV
Enter the patient’s MCV in the top field. The default is 90 fL (normal adult value). This is required for the calculation.
Enter Result
Input the known RDW value into either the RDW-CV (%) or RDW-SD (fL) field.
Automatic Conversion
The tool instantly calculates the equivalent value in the other unit based on the MCV provided.
Reset
Use the Clear button to reset all fields, including MCV.
Frequently Asked Questions
RDW-CV is a calculation: (Standard Deviation / Mean Corpuscular Volume) × 100. You cannot convert between SD and CV without knowing the MCV.
RDW-SD is a direct measurement and is not affected by the average size of the cell (MCV). RDW-CV can be artificially normal if both MCV and SD are elevated (e.g., in macrocytic anemia).