Progesterone to Estrogen Ratio (Pg/E2) Calculator
Enter your progesterone and estradiol lab values (in any common unit) and this calculator instantly computes your Pg/E2 ratio. It converts units automatically, classifies your result as balanced, estrogen-dominant, or progesterone-dominant, and shows the step-by-step arithmetic. Results are most meaningful for mid-luteal phase blood draws, typically 5-7 days after ovulation.
Formula
Worked example
A mid-luteal blood draw: progesterone 15 ng/mL, estradiol 100 pg/mL. Convert progesterone: 15 ng/mL x 1000 = 15,000 pg/mL. Estradiol is already in pg/mL. Ratio = 15,000 / 100 = 150. This falls in the balanced range (100-500).
What is the progesterone-to-estrogen ratio?
The Pg/E2 ratio is the numerical result of dividing your serum progesterone concentration by your serum estradiol (E2) concentration, after expressing both in the same unit (pg/mL). A single hormone level in isolation can look normal and yet mask an imbalance - for example, estradiol of 120 pg/mL is mid-luteal normal, but if progesterone is very low, the two hormones are out of proportion. The ratio captures that relationship in one number. Clinicians use it most often in reproductive medicine to assess luteal phase adequacy, guide progesterone supplementation decisions, and predict IVF outcome. Research on IVF cycles has found that higher estradiol relative to progesterone on trigger day is associated with better embryo development, while insufficient progesterone support after transfer is linked to implantation failure.
How the ratio is calculated and why units matter
The formula is simple: Pg/E2 = progesterone (pg/mL) / estradiol (pg/mL). The critical step is getting both values into the same unit before dividing. Laboratories report progesterone in ng/mL, nmol/L, or occasionally pg/mL, and estradiol in pg/mL, pmol/L, or ng/mL. Converting correctly makes a large difference: 15 ng/mL of progesterone equals 15,000 pg/mL. Dividing 15,000 by an estradiol of 100 pg/mL gives a ratio of 150, firmly in the balanced range. If you mistakenly divided 15 by 100, you would get 0.15, which would appear severely estrogen-dominant and be completely wrong. This calculator handles all conversions automatically using the molecular weights of progesterone (314.46 g/mol) and estradiol (272.38 g/mol).
When to test and how to interpret the result
Timing is everything. The ratio is only clinically meaningful when the blood draw takes place during the mid-luteal phase - typically day 19 to day 22 of a 28-day cycle, or 5 to 7 days after confirmed ovulation detected by LH surge or ultrasound. Outside that window, both hormones are naturally low, and the ratio tells you little. A balanced ratio of 100-500 during the mid-luteal phase suggests adequate progesterone relative to estradiol. A ratio below 100 is described as estrogen dominant, meaning progesterone is not providing sufficient counterbalance. A ratio above 500 often reflects exogenous progesterone from supplements, injections, or an early pregnancy. Postmenopausal women and those in follicular phase will have naturally lower ratios because progesterone levels are low throughout those phases - the 100-500 range does not apply.
Symptoms, limitations, and next steps
Estrogen dominance is associated with symptoms including bloating, breast tenderness, irregular or heavy periods, mood swings, fatigue, and difficulty maintaining weight. However, these symptoms overlap with many conditions, and the ratio alone is not a diagnosis. The Pg/E2 ratio is a screening tool, not a standalone diagnostic. Normal individual variation, lab-to-lab differences in assay calibration, and timing of the blood draw can all shift the number. Always interpret it alongside your full hormonal panel (FSH, LH, total estrogen, DHEA-S, testosterone, thyroid), your symptoms, and your cycle history. Work with a gynecologist, reproductive endocrinologist, or integrative physician who can place the result in your full clinical picture.
Pg/E2 ratio reference ranges (mid-luteal phase)
| Pg/E2 ratio | Classification | Clinical implication |
|---|---|---|
| < 100 | Estrogen dominant | Progesterone may be insufficient to buffer estradiol |
| 100 - 500 | Balanced (optimal) | Adequate progesterone relative to estradiol |
| > 500 | Progesterone dominant | Often from supplementation; verify with your doctor |
Reference ranges apply to mid-luteal phase blood draws. Individual lab reference intervals may differ.
Frequently asked questions
What is a good progesterone-to-estrogen ratio?
For mid-luteal phase blood draws (days 19-22 of a 28-day cycle, or 5-7 days after ovulation), a Pg/E2 ratio between 100 and 500 is generally considered balanced. Below 100 is classified as estrogen dominant - progesterone is low relative to estradiol. Above 500 is progesterone dominant, which most often reflects progesterone supplementation. These reference ranges assume both hormones are converted to pg/mL before dividing.
Why do I need to convert units before calculating the ratio?
The Pg/E2 ratio is only meaningful when both hormones are expressed in identical units. Laboratories report progesterone in ng/mL or nmol/L and estradiol in pg/mL or pmol/L. Because 1 ng/mL equals 1,000 pg/mL, dividing ng/mL by pg/mL without converting gives a number 1,000 times too small and appears as severe estrogen dominance when the values are actually balanced. This calculator converts everything to pg/mL automatically using the molecular weights of each hormone.
When should I get my blood drawn for this test?
For the most informative result, blood should be drawn during the mid-luteal phase - typically day 19 to day 22 of a standard 28-day cycle, or 5 to 7 days after a confirmed LH surge (positive ovulation test) or ultrasound-confirmed ovulation. If your cycle is longer or shorter, count 5-7 days from your likely ovulation date rather than from day 19. Morning fasting draws reduce within-day variability, but the timing within your cycle matters far more than the time of day.
Can the ratio be used to assess estrogen dominance?
Yes, the Pg/E2 ratio is one of the main tools clinicians use to assess relative estrogen dominance. A ratio below 100 in the mid-luteal phase suggests progesterone is not adequately opposing estradiol, even if each individual level appears within its own reference range. Common symptoms of estrogen dominance include heavy or irregular periods, bloating, breast tenderness, mood changes, and weight gain around the hips. However, the ratio is a screening marker, not a diagnostic test, and should be interpreted alongside symptoms and other labs.
How is this ratio used in IVF?
In assisted reproduction, the Pg/E2 ratio on the day of the trigger injection is monitored because a premature rise in progesterone before oocyte retrieval is associated with lower pregnancy rates. After embryo transfer, progesterone supplementation is given to support implantation, and the ratio may be tracked to ensure levels remain adequate. Some research suggests that maintaining a Pg/E2 ratio above 100 during the luteal support phase improves implantation rates. Your fertility clinic will use this alongside ultrasound and other hormone levels.
What if my ratio is above 500?
A ratio above 500 means progesterone is very high relative to estradiol. In naturally cycling women not on supplements, this can occur in early pregnancy, when progesterone rises sharply. More commonly, a ratio above 500 reflects exogenous progesterone from vaginal suppositories, oral capsules, or injections used in hormone therapy or IVF luteal support. Very high ratios from supplementation are not inherently harmful but should be reviewed with your prescribing physician to ensure dosing is appropriate.