Calculate your progesterone-to-estradiol ratio to assess hormonal balance, detect estrogen dominance, and support fertility and HRT monitoring.
The progesterone-to-estradiol (Pg:E2) ratio is a valuable clinical tool for assessing hormonal balance in women. This ratio helps identify estrogen dominance — a condition where estrogen levels are disproportionately high relative to progesterone, which can contribute to symptoms like heavy periods, bloating, mood swings, fibrocystic breasts, and fertility difficulties.
During the luteal phase of a normal menstrual cycle, progesterone should be the dominant hormone. An optimal Pg:E2 ratio during this phase typically falls between 100:1 and 500:1 (when both are measured in pg/mL). Ratios below 100:1 may indicate insufficient progesterone or excess estrogen, both of which are clinically significant.
This calculator converts between common lab units (ng/mL, nmol/L for progesterone; pg/mL, pmol/L for estradiol), computes the standardized ratio, and provides phase-specific interpretation. It's particularly useful for women monitoring fertility, evaluating PMS/PMDD symptoms, or tracking hormone replacement therapy (HRT) dosing. It keeps the two hormone values in one place so the ratio can be interpreted alongside the cycle phase that produced it. Check the example with realistic values before reporting.
The Pg:E2 ratio is most useful when progesterone and estradiol are interpreted together rather than as isolated values. This calculator keeps the phase context, unit conversion, and ratio calculation in one place so the result can be reviewed consistently across cycles or compared with other hormone measurements without changing the meaning of the underlying lab values.
Pg:E2 Ratio = (Progesterone in pg/mL) ÷ (Estradiol in pg/mL) Progesterone conversion: 1 ng/mL = 1,000 pg/mL = 3.18 nmol/L Estradiol conversion: 1 pg/mL = 3.671 pmol/L Optimal luteal ratio: 100–500:1
Result: Pg:E2 Ratio = 150:1 — Optimal luteal balance
Progesterone at 15 ng/mL = 15,000 pg/mL. Dividing by estradiol at 100 pg/mL gives a ratio of 150:1, which falls within the optimal range of 100–500:1 for the luteal phase.
The relationship between estrogen and progesterone governs much of female reproductive health. During a normal menstrual cycle, estrogen dominates the first half (follicular phase), stimulating the growth of the uterine lining and ovarian follicles. After ovulation, the corpus luteum produces large amounts of progesterone, which stabilizes the endometrium and prepares it for potential embryo implantation. If the balance shifts — typically due to anovulatory cycles, chronic stress, or declining ovarian function — symptoms can emerge.
Common causes of a low ratio include anovulatory cycles (no ovulation = no corpus luteum = no progesterone rise), chronic stress (cortisol competes with progesterone for receptors), xenoestrogens from environmental chemicals, excess body fat (adipose tissue produces estrone), and age-related decline in progesterone production, which typically begins in the late 30s. Identifying the underlying cause is essential for effective treatment.
The Pg:E2 ratio is used in fertility evaluation (adequate luteal progesterone is essential for embryo implantation), monitoring HRT effectiveness, evaluating PMS/PMDD severity, assessing perimenopause progression, and screening for luteal phase defects. While the ratio provides valuable information, it should always be interpreted alongside clinical symptoms and other laboratory findings.
During the luteal phase, an optimal ratio is typically 100–500:1 (both in pg/mL). Below 100:1 may indicate estrogen dominance. During the follicular phase, lower ratios are normal since progesterone is naturally low.
Estrogen dominance occurs when estrogen is disproportionately high relative to progesterone. It can cause heavy periods, bloating, breast tenderness, mood swings, weight gain, and fertility issues. It's diagnosed based on symptoms and hormone ratios, not absolute estrogen levels alone.
For the most informative Pg:E2 ratio, blood should be drawn on day 19–22 of your cycle (mid-luteal phase), approximately 7 days after ovulation. This is when progesterone should be at its peak.
While this calculator is designed for female hormone assessment, men can experience estrogen-progesterone imbalance too. However, the reference ranges and interpretations are specific to female physiology.
Hormone replacement therapy aims to restore physiological hormone balance. Target ratios during HRT are typically 100–300:1. Your prescribing provider will adjust doses based on lab results and symptoms.
A very high Pg:E2 ratio (>500:1) in the luteal phase could indicate excess progesterone supplementation or very low estradiol levels. This can cause fatigue, drowsiness, and mood changes. Discuss with your doctor.