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, shows the step-by-step arithmetic, and places the result on the 100-500 scale popularised by functional-medicine practitioners. Important: no medical body defines a reference range for this ratio, and "estrogen dominance" is not a recognised medical diagnosis. Treat the classification below as general interest rather than medical advice, and take any hormone questions to your doctor.
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, which sits inside the commonly quoted 100-500 band. That band is a convention rather than a validated reference interval, so the number is a talking point rather than a result.
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. Where it has been studied formally is assisted reproduction, where the progesterone-to-estradiol ratio on the day of the trigger injection has been examined as a predictor of cycle outcome. Outside that setting it is mainly a functional-medicine tool: no professional body defines a Pg/E2 reference range, and "estrogen dominance" is not a diagnosis recognised by the Endocrine Society, ACOG, or the major menopause societies. This page is general interest, not medical advice.
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 ratio of 100-500 during the mid-luteal phase is what this scale treats as balanced. A ratio below 100 is what it calls estrogen dominant, and a ratio above 500 usually reflects exogenous progesterone from supplements or injections, or an early pregnancy. Two cautions are worth spelling out. First, the 100-500 band is a convention circulated by functional-medicine practitioners and hormone-testing companies; it is not a laboratory reference interval and no guideline body has published or validated it. Second, the band is narrower than normal physiology: with ordinary mid-luteal values of progesterone 11-29 ng/mL and estradiol 19-160 pg/mL, the arithmetic gives ratios from roughly 70 to 1,500, so plenty of perfectly typical results land outside 100-500. Postmenopausal women and those in the follicular phase will have much lower ratios because progesterone is low throughout those phases, and the band does not apply to them at all.
Symptoms, limitations, and next steps
The symptom list usually attached to estrogen dominance includes bloating, breast tenderness, irregular or heavy periods, mood swings, fatigue, and difficulty maintaining weight. Every one of those overlaps with thyroid disease, perimenopause, stress, anaemia, and a long list of other causes, so none of them points to a hormone ratio on its own. The Pg/E2 ratio is not a validated screening test and it is certainly not a diagnosis. 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.
The commonly quoted Pg/E2 bands (mid-luteal phase)
| Pg/E2 ratio | Term used for it | What people take it to mean |
|---|---|---|
| < 100 | Called "estrogen dominant" | Progesterone low relative to estradiol; not a diagnosis |
| 100 - 500 | Called "balanced" | The band this scale treats as typical |
| > 500 | Called "progesterone dominant" | Usually reflects supplementation or early pregnancy |
These bands come from functional-medicine practice, not from a professional guideline or a laboratory reference interval. No medical body publishes a Pg/E2 reference range. Use them as general interest only and discuss any hormone concerns with your doctor.
Frequently asked questions
What is a good progesterone-to-estrogen ratio?
There is no official answer, because no medical body publishes a reference range for this ratio. The figure you will see quoted almost everywhere is 100 to 500 for a mid-luteal blood draw (days 19-22 of a 28-day cycle, or 5-7 days after ovulation), with below 100 called estrogen dominant and above 500 called progesterone dominant. That band comes from functional-medicine practice rather than from a guideline or a validated study, and ordinary mid-luteal lab values can produce ratios well outside it. Both hormones must be converted to pg/mL before dividing for the number to mean anything at all.
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?
Only loosely. "Estrogen dominance" is not a recognised medical diagnosis - Cleveland Clinic describes it as a term that "some healthcare providers call this", and there are no accepted laboratory thresholds for it. Practitioners who use the concept read a mid-luteal ratio below 100 as progesterone not adequately opposing estradiol, even when each hormone sits inside its own reference range. The symptoms usually cited (heavy or irregular periods, bloating, breast tenderness, mood changes, weight gain) are real but non-specific. Treat the ratio as a talking point for your doctor, not as a test result that means something on its own.
How is this ratio used in IVF?
Assisted reproduction is the one setting where a progesterone-to-estradiol ratio has been studied formally. It is watched on the day of the trigger injection because a premature rise in progesterone before oocyte retrieval is associated with lower pregnancy rates. Be aware that the IVF literature works with a completely different scale from the 100-500 band on this page: trigger-day estradiol is supraphysiologically high, so the same arithmetic produces ratios around 1, and thresholds in those studies sit near 1 rather than near 100. Do not read an IVF result against this calculator, and do not read this calculator against IVF cut-offs. Your fertility clinic interprets the numbers alongside ultrasound and your full hormone panel.
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.
Sources
- Bourgain C, Devroey P. The endometrium in stimulated cycles for IVF. Hum Reprod Update. 2003.
- Prior JC. Progesterone for Symptomatic Perimenopause Treatment. Climacteric. 2018.
- Cleveland Clinic - High Estrogen (notes that "estrogen dominance" is a term used by some providers, and gives no Pg/E2 reference range)