ng/mL to IU/mL Calculator

By: Patrick Myers Patrick Myers is the CEO and Founder of Calculator Academy. He has over eight years of experience developing online calculators and holds a B.S. in Mechanical Engineering. His work focuses on formula implementation, calculator accuracy, unit conversions, and creating practical tools that are easy to use.

Last Updated: July 3, 2026
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This calculator was built with Calculator Academy’s community calculator studio with AI assistance, and was reviewed by the Calculator Academy team before publication.

About the ng/mL to IU/mL Calculator

This converter changes a concentration in ng/mL into IU/mL using a potency factor for the specific substance being measured. It is useful for supplement comparisons, lab interpretation, and assay calculations where biological activity, not just mass, determines the unit conversion.

How to use this calculator

  1. Enter the concentration value in ng/mL.
  2. Choose a reference standard preset, such as vitamin D, vitamin A retinol, or human insulin.
  3. Select Custom factor if your substance or lab report uses a different standard.
  4. Choose the factor format: IU per ng, IU per µg, IU per mg, or ng per IU.
  5. Enter the potency factor value if using a custom factor.
  6. Read the converted IU/mL, µIU/mL, IU per ng, ng per IU, and table values.

How it works

International units are based on biological activity, so the conversion from ng/mL to IU/mL depends on the substance and reference standard. The calculator first converts the selected factor into a common form: IU per ng.

If the factor is entered as IU per µg, it is divided by 1,000. If it is entered as IU per mg, it is divided by 1,000,000. If it is entered as ng per IU, the calculator uses its reciprocal to get IU per ng.

The main formula is IU/mL = ng/mL × IU per ng. The calculator also reports µIU/mL by multiplying IU/mL by 1,000,000 and reports ng per IU as 1 divided by IU per ng.

Results are educational estimates and should not replace professional medical, laboratory, regulatory, or product-specific guidance. Always confirm the correct potency factor for the exact substance and reference standard you are using.

Example calculation

Using the default vitamin D setting, enter 25 ng/mL and choose Vitamin D2/D3: 40 IU per µg. Since 40 IU per µg equals 0.04 IU per ng, the calculation is 25 × 0.04 = 1.000 IU/mL. The same result is 1,000,000 µIU/mL, and the reciprocal factor is 25 ng per IU.

Frequently asked questions

Is there one universal conversion from ng/mL to IU/mL?

No. IU measures biological activity, so the correct conversion depends on the substance and reference standard.

How do I convert IU per µg to IU per ng?

Divide IU per µg by 1,000 because 1 µg equals 1,000 ng.

Why does vitamin D use 40 IU per µg?

For common vitamin D2/D3 references, 1 µg is treated as 40 IU, which means 1 ng equals 0.04 IU.

Can I use this for insulin lab values?

You can use the human insulin preset or enter your lab’s factor, but confirm the assay standard because insulin reporting can vary.

What happens if I enter ng per IU instead of IU per ng?

The calculator takes the reciprocal of ng per IU to get IU per ng before multiplying by the concentration.