The calculation of progesterone to estrogen ratio, also known as Pg/E2 or P/E2 ratio, is an essential part of female hormone balance assessment and success prediction of in vitro fertilization (IVF).
You can also use this calculator for estradiol and progesterone unit conversion by simply clicking on units to switch between ng/mL, pg/mL, and nmol/L for progesterone and pg/mL, ng/mL, and pmol/L for estradiol.

Estradiol (E2) belongs to estrogens, a group of female sex hormones. Other major estrogens are: estrone (E1) and estriol (E3). Because estradiol is the most potent and most frequently measured, its concentration is used in the progesterone to estradiol ratio estimation.

Step one - estradiol and progesterone unit conversion

The main difficulty in calculating the progesterone to estrogen ratio is usually caused by the fact that the concentrations of the hormones are presented in different units. Progesterone is most commonly presented in ng/mL (nanogram per liter) or nmol/L (nanomole per liter), and estradiol is presented in pg/mL (picogram per milliliter) or pmol/L (picomole per liter). To be able to compare the two, it's necessary to express them in the same units.

  • Progesterone:

1 ng/mL = 3.180547 nmol/L

  • Estradiol:

1 pg/mL = 3.6713 pmol/L

Then, to go from ng/mL to pg/mL, multiply the value by 1000, or to go from pg/mL to ng/mL, divide it by 1000.

If you're confused with the unit conversion of other lab test results, check out our cholesterol unit and glucose unit converters!

Step two - estimation of the progesterone to estradiol ratio

After bringing the hormone concentrations to the same unit of measure, the calculation of the P/E2 ratio itself is very simple:

ratio = progesterone / estradiol

What is progesterone to estrogen ratio used for?

It is a parameter used to determine hormonal dominance in patients with results within normal ranges of progesterone and estradiol (measured in luteal phase of the menstrual cycle):

  • Progesterone (P or Pg): 11 - 29 ng/mL or 35 - 92 nmol/L
  • Estradiol (E2): 19 - 160 pg/mL or 70 - 600 pmol/L In healthy women, progesterone/estradiol ratio should be between 100 and 500. If it's higher than that, it may indicate progesterone domination, and if it's lower, then estrogen domination is more likely.

A specific progesterone and estradiol balance is especially important for successful conception and is estimated before the procedure of in vitro fertilization (IVF), but as the concentration of estradiol is crucial here, the ratio is usually inversed. If you're interested about this topic, check out these articles by dr. Rehana Rehman and dr. Irmhild Gruber:

Females having high estradiol/ progesterone ratio were able to achieve clinical pregnancy shown by a positive βhCG and cardiac activity on transvaginal scan. These females also had significantly high number of oocytes, endometrial thickness and implantation rate. Conclusion: A high estradiol/progesterone ratio on the day of ovulation induction predicts the success of intra cytoplasmic sperm injection.

During IVF-ET, controlled ovarian hyperstimulation results in excessive follicular development and supraphysiologic serum concentrations of E2 and P.

Małgorzata Koperska, MD

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