How to Convert Progesterone ng/mL to nmol/L
Progesterone is reported in ng/mL in the US and in nmol/L across most of the world. The conversion factor is 3.18, from progesterone's molecular weight of 314.46 g/mol.
Progesterone nmol/L = progesterone ng/mL × 3.18 Progesterone ng/mL = progesterone nmol/L ÷ 3.18 Progesterone ng/mL to nmol/L Chart
| ng/mL | nmol/L | Typical context |
|---|---|---|
| 1 ng/mL | 3.2 nmol/L | Follicular phase |
| 3 ng/mL | 9.5 nmol/L | Minimum post-ovulation |
| 5 ng/mL | 15.9 nmol/L | Reliable ovulation marker |
| 10 ng/mL | 31.8 nmol/L | Mid-luteal — ovulation confirmed |
| 20 ng/mL | 63.6 nmol/L | Strong luteal |
| 44 ng/mL | 139.9 nmol/L | 1st-trimester upper |
nmol/L to ng/mL Reverse Chart
| nmol/L | ng/mL |
|---|---|
| 3.2 nmol/L | 1.0 ng/mL |
| 15.9 nmol/L | 5.0 ng/mL |
| 31.8 nmol/L | 10.0 ng/mL |
| 92 nmol/L | 28.9 ng/mL |
Progesterone Reference Ranges
| Phase / status | ng/mL | nmol/L |
|---|---|---|
| Follicular phase | Below 1 ng/mL | Below 3.2 nmol/L |
| Ovulation / early luteal | 3–5 ng/mL | 9.5–15.9 nmol/L |
| Mid-luteal (day ~21) | 11–29 ng/mL | 35–92 nmol/L |
| 1st trimester pregnancy | 11–44 ng/mL | 35–140 nmol/L |
Day-21 Progesterone: Confirming Ovulation
The most common reason to test progesterone is to confirm ovulation. It is drawn about 7 days after ovulation — often day 21 of a 28-day cycle, or 7 days before the next expected period. A mid-luteal progesterone above 10 ng/mL (31.8 nmol/L) is the classic sign that ovulation occurred; some labs use a lower 3–5 ng/mL (9.5–15.9 nmol/L) threshold for post-ovulation. Timing is everything: a low value simply because it was drawn too early can be mistaken for a problem.
Worked Example
Suppose a report shows 92 nmol/L on a day-21 sample and you want ng/mL:
92 ÷ 3.18 = 28.9 ng/mL 28.9 ng/mL is a strong luteal level consistent with ovulation. Converting the other way, the 10 ng/mL confirmation threshold is 31.8 nmol/L.
Frequently Asked Questions
How do you convert progesterone ng/mL to nmol/L?
Multiply ng/mL by 3.18. For example, 10 ng/mL is about 31.8 nmol/L.
What level confirms ovulation?
A mid-luteal (day ~21) progesterone above 10 ng/mL (31.8 nmol/L).
When should progesterone be tested?
About 7 days after ovulation — day 21 of a 28-day cycle, or 7 days before the next period.
What is normal in early pregnancy?
Roughly 11–44 ng/mL (35–140 nmol/L) in the first trimester.
References
- Medscape — Progesterone: Reference Range and Interpretation.
- Progesterone factor 3.18 (MW 314.46 g/mol); mid-luteal ovulation-confirmation threshold > 10 ng/mL from standard fertility references.
Conclusion
Converting progesterone between ng/mL and nmol/L is a ×3.18. For ovulation and fertility, the value only means something next to the cycle day it was drawn — pair the result with timing and your clinician's interpretation.