What this result means
For total vitamin B12, multiply pg/mL by 0.7378 to get pmol/L. Divide pmol/L by 0.7378 to get pg/mL. The result is rounded once to two decimals. The Siemens Atellica IM Vitamin B12 assay instructions publish this conversion factor. [1]
Match the test and its unit first
Check that the report says total vitamin B12, choose the direction matching its printed unit, then enter the number alone. Changing direction clears the entry so the same digits are not silently assigned a different unit. Keep the original report beside the result.
Why this calculator uses 0.7378
The Results section of the Siemens Atellica IM Vitamin B12 instructions gives 1 pg/mL = 0.7378 pmol/L. This calculator uses that published convention and its reciprocal. A laboratory may print a rounded conversion; retain its original reported value when comparing results. [1]
The software represents 0.7378 as 3689/5000, so it can calculate the declared factor without first shortening the reverse factor. Exact arithmetic does not remove physical or assay uncertainty.
What if my report says ng/L?
One picogram per millilitre is one nanogram per litre: both equal one billionth of a gram per litre. The SI prefixes give this unit identity. For total B12, enter the same numeric ng/L value in the pg/mL direction; do not apply an extra factor of 1,000. [2]
Keep the original precision
The answer displays two decimals. For example, 25 pg/mL gives 18.445 pmol/L before rounding, displayed as 18.45. The reverse direction divides by 0.7378 before rounding, rather than multiplying by a shortened reciprocal.
Two displayed decimals do not mean your laboratory measured to that precision. Copy the original value and unit when sharing a clinical result.
Zero, small values and reporting limits
A true zero displays as 0.00. A positive result below the two-decimal display resolution appears as less than 0.01, instead of being presented as an exact zero.
A report such as less than 100 contains a limit, not an exact measured value of 100. This tool rejects inequality signs and does not infer a measurement behind a reporting limit.
Total B12, active B12 and supplement amounts are different
This page only rewrites a total B12 concentration. It cannot turn total B12 into an active B12 or methylmalonic acid result. Use the test name and reference interval printed by your laboratory; identical units do not make different tests interchangeable. [3]
Concentration describes an amount per volume. A supplement label or injection dose describes an amount. This tool has no information that would convert a blood result into a dose. [2]
Accepted and rejected entries
Use a decimal point. Blank, negative and above-limit entries are rejected, as are commas, fractions, scientific notation, unit text and non-finite values. The upper bound is technical and has no clinical meaning.
Share the page without your result
No account is needed. Inputs and results stay in browser memory. Share uses the clean page address; reset or reload clears the entry. The optional recently-used list stores a tool identifier, not your vitamin B12 value.
Interpret the original report with clinical context
This calculator provides no risk color, reference range or diagnosis. A unit change cannot decide whether a B12 result is adequate or explain symptoms. Discuss interpretation and follow-up with the clinician responsible for the test. [3]
Formula and assumptions
- Version
- Total vitamin B12 mass and amount concentration conversion, total-b12-pgml-pmoll-0-7378-v1
- Rounding
- Multiply by 3689/5000 or its exact reciprocal 5000/3689; round once to two decimals with halfway ties upward. Tiny positive results use a less-than sign. Physical measurement uncertainty remains.
- Worked example
- Arithmetic example only: 200.00 pg/mL × 0.7378 = 147.56 pmol/L. Dividing 147.56 pmol/L by 0.7378 gives 200.00 pg/mL. These numbers demonstrate the conversion; they are not a normal range or treatment target. [1]
Who this is for — and when not to use it
Intended use
Neutral arithmetic conversion of an existing total vitamin B12 concentration between pg/mL and pmol/L using the declared 0.7378 convention.
Not intended for
No high/low classification, reference-range selection, deficiency diagnosis, active B12 conversion, dose calculation, treatment advice or assessment of whether a result requires urgent care.
Exclusions
- Active B12 (holotranscobalamin), methylmalonic acid and other different measurements
- Vitamin B12 doses in tablets, food or injections
- Changing a specimen, assay method or laboratory reference interval
- Diagnosis, treatment, screening and urgent triage decisions
- Reporting limits with less-than or greater-than signs treated as exact measurements
Evidence sources
- 1. Atellica IM Vitamin B12 (VB12): Instructions for Use, revision 03, Results (page 9) — Siemens Healthineers. Accessed Sep 21, 2026.
- 2. Guide to the SI: Units and Prefixes — National Institute of Standards and Technology. Accessed Sep 21, 2026.
- 3. Active B12 (Holotranscobalamin): background information — Gloucestershire Hospitals NHS Foundation Trust. Accessed Sep 21, 2026.