nmol/L to ng/mL Converter

If your lab report says nmol/L and you’re used to reading ng/mL, you already know the numbers don’t match up in any simple way. A vitamin D result of 50 nmol/L isn’t 50 ng/mL, and it isn’t half of it either. The gap between these two units depends on the molecule you’re measuring, not on some fixed rule you can memorize once and reuse everywhere.

This mix-up shows up a lot with vitamin D, testosterone, cortisol, progesterone, and estradiol results, since labs in different countries report the same hormone in different units. Here’s how the conversion actually works, plus a chart and real examples so you’re not guessing.

Why There’s No Single Conversion Number

nmol/L measures how many molecules are in a liter, no matter how big or small those molecules are. ng/mL measures the actual weight of the substance in a smaller volume. To go from a molecule count to a weight, you need to know how much one molecule weighs — its molecular weight. That’s why 50 nmol/L of vitamin D converts to a different number than 50 nmol/L of testosterone. Each hormone has its own molecular weight, so each one needs its own multiplier.

The nmol/L to ng/mL Formula

The formula is straightforward once you have the molecular weight (MW) of the substance, in grams per mole:

ng/mL = (nmol/L × MW) ÷ 1,000

To reverse it and go from ng/mL back to nmol/L, divide instead of multiply:

nmol/L = (ng/mL × 1,000) ÷ MW

You don’t need to do this by hand every time. Our nmol/L to ng/mL converter has the molecular weights for common hormones and vitamins already built in, so you just pick the molecule, type in your number, and get an instant, accurate result in either direction.

nmol/L to ng/mL Conversion Chart by Molecule

Vitamin D: nmol/L to ng/mL

Vitamin D (25-hydroxyvitamin D) is the most common conversion people search for, since the UK, Canada, and much of Europe report it in nmol/L while the US typically uses ng/mL. With a molecular weight of 400.64 g/mol, here’s what common lab values look like on both scales:

• 30 nmol/L = 12.02 ng/mL
• 40 nmol/L = 16.03 ng/mL
• 50 nmol/L = 20.03 ng/mL
• 75 nmol/L = 30.05 ng/mL
• 100 nmol/L = 40.06 ng/mL
• 150 nmol/L = 60.10 ng/mL
• 200 nmol/L = 80.13 ng/mL

As a rough guide, most labs consider vitamin D levels below 50 nmol/L (20 ng/mL) insufficient, and 75 nmol/L (30 ng/mL) or above sufficient — but always check the reference range printed on your own lab report, since ranges vary slightly by lab and by country.

Testosterone: nmol/L to ng/mL

Total testosterone has a molecular weight of 288.42 g/mol. A result of 20 nmol/L works out to 5.77 ng/mL, and 30 nmol/L converts to 8.65 ng/mL. These figures are for total testosterone; free testosterone is reported in much smaller units (pg/mL or pmol/L) and needs a different calculator.

Cortisol, Progesterone, and Estradiol

Cortisol (MW 362.46) at 500 nmol/L converts to 181.23 ng/mL — a typical morning value. Progesterone (MW 314.47) at 30 nmol/L works out to 9.43 ng/mL, which is a common threshold used to confirm ovulation. Estradiol (MW 272.38) is measured in much smaller amounts, so 1 nmol/L equals 0.27 ng/mL, and most results sit well below whole numbers.

Is nmol/L the Same as nM?

Yes. nM (nanomolar) and nmol/L are two names for the same unit, so any nmol/L to ng/mL conversion works exactly the same way for nM. Don’t confuse either of these with pmol/L, though — a picomole is a thousand times smaller than a nanomole, so a result in pmol/L needs to be divided by 1,000 before you apply the nmol/L formula.

How to Use the Converter

• Pick your direction: nmol/L to ng/mL, or ng/mL back to nmol/L.
• Select the molecule from the dropdown — vitamin D, testosterone, cortisol, progesterone, estradiol, and others are already set up with the correct molecular weight.
• Type in your lab value and get the converted result immediately, with no manual math.
• Testing a substance that isn’t listed? Choose Custom molecular weight and enter the MW yourself — you can usually find it on the lab report or a drug reference sheet.

Frequently Asked Questions

What is the formula to convert nmol/L to ng/mL?

Multiply the nmol/L value by the molecule’s molecular weight, then divide by 1,000: ng/mL = (nmol/L × MW) ÷ 1,000.

How do I convert vitamin D from nmol/L to ng/mL?

Multiply the nmol/L value by 400.64 (vitamin D’s molecular weight) and divide by 1,000. For example, 50 nmol/L equals 20.03 ng/mL.

Why can’t I use one number for every hormone?

Because nmol/L counts molecules and ng/mL measures weight, and different molecules weigh different amounts. Each substance needs its own molecular weight in the formula.

Is nmol/L to ng/mL conversion the same for testosterone and progesterone?

No. Testosterone uses a molecular weight of 288.42 g/mol, while progesterone uses 314.47 g/mol, so the same nmol/L number converts to two different ng/mL results.

Use the nmol/L to ng/mL converter above to convert vitamin D, testosterone, cortisol, progesterone, estradiol, and other lab values instantly, in either direction.