pmol/L to pg/mL Converter (and pg/mL to pmol/L)
pmol/L to pg/mL Conversion Chart (per 1 pmol/L)
| Molecule | MW (g/mol) | 1 pmol/L equals |
|---|---|---|
| Estradiol (E2) | 272.38 | 0.2724 pg/mL |
| Progesterone | 314.47 | 0.3145 pg/mL |
| Testosterone | 288.42 | 0.2884 pg/mL |
| Cortisol | 362.46 | 0.3625 pg/mL |
| Free T3 | 651.01 | 0.6510 pg/mL |
| Free T4 | 776.87 | 0.7769 pg/mL |
| PTH | 9500 | 9.5 pg/mL |
| Insulin | 5808 | 5.808 pg/mL |
| Vitamin B12 | 1355.4 | 1.3554 pg/mL |
| Folate | 441.4 | 0.4414 pg/mL |
pmol/L is a molar concentration (a count of molecules) while pg/mL is a mass concentration, so the molecular weight of the chosen substance is required to convert between them — larger molecules produce a larger pg/mL value for the same pmol/L. Estradiol is one of the most common searches for this conversion since many labs report it in pmol/L while many US reference ranges use pg/mL. For anything not listed, use the Custom molecular weight option and confirm against a published reference.
Popular pmol/L to pg/mL Conversions
What Do pmol/L and pg/mL Actually Mean?
pg/mL stands for picograms per millilitre — a picogram is one trillionth of a gram. It’s a mass concentration: how much a substance weighs in a given volume of blood.
pmol/L stands for picomoles per litre — a picomole is one trillionth of a mole, and a mole is simply a fixed count of molecules (about 6.022 × 10²³ of them). It’s a molar concentration: how many molecules of a substance are present in a given volume of blood, regardless of how much any individual molecule weighs.
Both units describe concentration, but one counts molecules and the other weighs them — which is exactly why converting between them needs one extra piece of information: the substance’s molecular weight.
pmol/L to pg/mL: Why There’s No Single Number to Memorize
If you searched “pmol/L to pg/mL” hoping for one clean multiplier the way some unit conversions give you one, here’s the catch: there isn’t one. Search that exact phrase and you’ll find factors that flatly contradict each other.
One page says multiply by 0.27, another says 1.36, and a third says 0.65. None of them are wrong — they’re simply answering the question for completely different substances, and the page often doesn’t make that obvious until several paragraphs later.
Is There One Conversion Factor for pmol/L to pg/mL?
No, and this is the single most important thing to understand before you convert anything.
pmol/L counts molecules. pg/mL measures their weight. The bridge between a molecule count and a weight is the molecule’s molecular weight, and molecular weight is different for every substance — sometimes dramatically different.
Estradiol and Vitamin B12 are both commonly reported in these units, but their molecular weights are nowhere close to each other. As a result, their conversion factors aren’t close either.
Why the Same Two Units Convert Differently for Every Hormone
A picomole of a small, light molecule weighs very little. A picomole of a large, heavy molecule weighs much more, even though it’s still exactly one picomole of material.
Vitamin B12 (Cobalamin) has a molecular weight of approximately 1,355 g/mol, making it a relatively heavy molecule. Estradiol has a molecular weight of only 272 g/mol.
Convert the same pmol/L value for both substances and Vitamin B12 will produce a pg/mL value roughly five times larger than estradiol. Nothing is wrong with the math — that difference simply reflects the size of the molecules.
The Actual Formula
pg/mL = pmol/L × molecular weight (g/mol) ÷ 1000
Reverse conversion (pg/mL to pmol/L):
pmol/L = pg/mL × 1000 ÷ molecular weight (g/mol)
The molecular weight is doing all the work in these formulas. Use the correct molecular weight for your specific substance and the calculation is straightforward. Use the wrong molecular weight — even one that seems reasonable — and you’ll get a precise but completely incorrect result.
Worked Examples
Estradiol: 367 pmol/L to pg/mL
Estradiol molecular weight = 272.38 g/mol
367 × 272.38 ÷ 1000 = 99.98 pg/mL
Vitamin B12: 300 pmol/L to pg/mL
Vitamin B12 molecular weight = 1,355.4 g/mol
300 × 1355.4 ÷ 1000 = 406.6 pg/mL
Free T3: 6 pmol/L to pg/mL
Free T3 molecular weight = 651.01 g/mol
6 × 651.01 ÷ 1000 = 3.9 pg/mL
Reverse example — Vitamin B12: 400 pg/mL to pmol/L
400 × 1000 ÷ 1355.4 = 295.2 pmol/L
Notice how differently similar input values produce different results, and how the same formula runs equally well in either direction. The molecular weight — not the calculation — is responsible for the difference.
What Happens If You Use the Wrong Factor
Imagine you’re converting a Vitamin B12 result but accidentally use an estradiol conversion factor because a website doesn’t clearly identify which substance the factor belongs to.
Using 300 pmol/L:
- Correct Vitamin B12 conversion: 406.6 pg/mL
- Incorrect estradiol conversion: about 82 pg/mL
That’s not a small rounding error. It’s approximately a five-fold difference, potentially making a normal result appear severely deficient. Always verify that the molecular weight belongs to the exact substance shown on your laboratory report.
Common Substances and Their Conversion Factors
| Substance | Molecular Weight (g/mol) | Multiply pmol/L by |
|---|---|---|
| Estradiol (E2) | 272.38 | 0.272 |
| Vitamin B12 (Cobalamin) | 1355.4 | 1.355 |
| Free T3 | 651.01 | 0.651 |
| Free T4 | 776.87 | 0.777 |
| Parathyroid Hormone (PTH) | 9500 | 9.5 |
| Progesterone | 314.47 | 0.314 |
| Testosterone | 288.42 | 0.288 |
What About nmol/L?
Some labs report results in nmol/L (nanomoles per litre) rather than pmol/L. A nanomole is 1,000 times larger than a picomole, so 1 nmol/L = 1,000 pmol/L. To go from nmol/L to pg/mL, multiply the nmol/L value by 1,000 to get pmol/L first, then apply the same molecular-weight formula above — or simply enter the value in this calculator as pmol/L after converting it yourself, since the underlying molecular-weight math is identical.
A Word on Reference Ranges
After converting your value correctly, compare it with the reference range printed on your own laboratory report rather than a generic chart.
Reference ranges can vary depending on:
- Sex
- Age
- Menstrual cycle phase
- Pregnancy status
- Laboratory assay
- Reporting units
The Short Version
There is no universal pmol/L to pg/mL conversion factor. The correct calculation always depends on the molecular weight of the substance being measured.
Use this formula:
pg/mL = pmol/L × molecular weight (g/mol) ÷ 1000
Whether you’re converting estradiol, Vitamin B12, Free T3, Free T4, testosterone, progesterone, or another substance, the molecular weight determines the correct answer. Rather than looking up molecular weights manually every time, the pmol/L to pg/mL converter above includes the correct conversion factors for estradiol, Vitamin B12, Free T3, Free T4, PTH, insulin, and other common laboratory substances — in both directions — helping you avoid costly conversion mistakes.
Frequently Asked Questions
Is pg/mL the same as pmol/L?
No. pg/mL (picograms per millilitre) is a mass concentration, while pmol/L (picomoles per litre) is a molar concentration that counts molecules rather than weighing them. The two are only convertible once you know the molecular weight of the specific substance being measured, using the formula pg/mL = pmol/L × molecular weight (g/mol) ÷ 1000.
What does pg/mL mean?
pg/mL stands for picograms per millilitre. A picogram is one trillionth (10⁻¹²) of a gram, so pg/mL expresses how many trillionths of a gram of a substance are present in each millilitre of a sample such as blood serum. It is a common unit for reporting very low concentrations of hormones, vitamins and other lab markers.
How do I convert pg/mL to pmol/L?
Use the formula pmol/L = pg/mL × 1000 ÷ molecular weight (g/mol). For example, 400 pg/mL of Vitamin B12 (molecular weight 1355.4 g/mol) converts to 400 × 1000 ÷ 1355.4 ≈ 295.2 pmol/L. The calculator above handles this automatically — just set Direction to “pg/mL → pmol/L” and pick the correct substance.
How do I convert estradiol pmol/L to pg/mL?
Multiply the pmol/L value by estradiol’s molecular weight (272.38 g/mol) and divide by 1000. For example, 367 pmol/L of estradiol converts to approximately 99.98 pg/mL. Estradiol is one of the most frequently converted hormones between these two units since many labs report it in pmol/L while many US reference ranges use pg/mL.
How do I convert Vitamin B12 pmol/L to pg/mL?
Multiply the pmol/L value by Vitamin B12’s molecular weight (1355.4 g/mol) and divide by 1000. For example, 300 pmol/L of Vitamin B12 converts to approximately 406.6 pg/mL. Because Vitamin B12 is a much heavier molecule than estradiol, using an estradiol factor by mistake would understate the true value by roughly five-fold.
Why do different websites give different pmol/L to pg/mL conversion factors?
Because each website is usually answering the question for a different substance without saying so clearly. There is no single, universal pmol/L to pg/mL factor — the correct multiplier always depends on the molecular weight of the exact substance on your lab report, so a factor that is correct for estradiol will be wrong for Vitamin B12, PTH, or any other analyte.
What is the difference between nmol/L and pmol/L?
Both are molar concentration units, but they differ by a factor of 1,000: 1 nmol/L (nanomole per litre) equals 1,000 pmol/L (picomoles per litre). If your lab report uses nmol/L, multiply by 1,000 to get pmol/L first, then apply the same molecular-weight formula to convert to pg/mL.
Is this pmol/L to pg/mL converter free to use?
Yes, the calculator above is free to use for any of the included substances — Estradiol, Progesterone, Testosterone, Cortisol, Free T3, Free T4, PTH, Insulin, Vitamin B12 and Folate — as well as any other substance via the Custom molecular weight option.
