Calculate the progesterone-to-estradiol ratio, convert common lab units, and review the result in cycle-phase or hormone-monitoring context.
The progesterone-to-estradiol (Pg:E2) ratio is a way to review progesterone and estradiol on the same scale instead of reading each lab value in isolation. The ratio can be useful as cycle-phase context, especially when the question is whether luteal-phase progesterone rose as expected relative to estradiol in the sample that was drawn.
Progesterone and estradiol change substantially across the menstrual cycle, which is why the timing of the blood draw usually matters more than any single universal cutoff. The same ratio can mean very different things in the follicular phase, mid-luteal phase, perimenopause, or during hormone therapy.
This calculator converts common lab units, computes the standardized ratio, and keeps the ratio beside the cycle phase selected by the user. It is best used as a hormone-review worksheet rather than as a stand-alone diagnosis of "estrogen dominance" or luteal dysfunction.
Progesterone and estradiol are often discussed together, but they are frequently reported in different units and drawn at different points in the cycle. This page keeps the unit conversion, ratio calculation, and phase context in one place so the numbers can be reviewed more consistently.
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.
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This page converts progesterone and estradiol into common units, then divides progesterone in pg/mL by estradiol in pg/mL to show a simple Pg:E2 ratio. The interpretation bands are intended only as cycle-phase context so the ratio can be reviewed alongside the actual hormone values and the timing of the blood draw.
The result is not a validated stand-alone diagnosis of luteal-phase deficiency, estrogen dominance, or treatment need. Ovulation timing, assay method, symptoms, fertility history, and the broader endocrine workup still matter more than the ratio alone.
The ratio is most useful when it is read in the context of cycle timing and the assay units used. Mid-luteal ratios are usually much higher than follicular ratios because progesterone rises after ovulation. This page shows broad worksheet bands, but the ratio is not a universally standardized diagnostic cutoff.
No. A lower ratio can reflect low progesterone, higher estradiol, cycle-timing issues, an anovulatory cycle, perimenopausal variability, or hormone therapy timing. The ratio is a context clue, not a stand-alone diagnosis.
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.