About the progesterone to estrogen (Pg:E2) ratio
Progesterone (P4) and estradiol (E2) are usually reported by the lab in different units — progesterone in nanograms per milliliter (ng/mL) and estradiol in picograms per milliliter (pg/mL). Because 1 ng/mL equals 1000 pg/mL, the two values cannot be divided directly without first converting them to the same scale. This calculator performs that conversion, then divides the standardized progesterone figure by the standardized estradiol figure to produce a single Pg:E2 ratio.
The formula
Ratio = (Progesterone in ng/mL x 1000) / Estradiol in pg/mL
If your lab report uses SI units instead (nmol/L for progesterone, pmol/L for estradiol), convert to ng/mL and pg/mL first using standard molar conversion factors — approximately 1 ng/mL progesterone = 3.18 nmol/L, and 1 pg/mL estradiol = 3.67 pmol/L — then apply the formula above. This calculator handles that conversion automatically when you select the SI unit options.
Why the ratio moves across the cycle
Estradiol is the dominant hormone in the follicular (pre-ovulation) phase, while progesterone stays low. After ovulation, the corpus luteum begins producing progesterone in much larger amounts, so the Pg:E2 ratio rises sharply through the luteal phase and falls again if pregnancy does not occur. Because of this normal swing, the same numeric ratio can be unremarkable on one cycle day and unusual on another — the collection date matters as much as the numbers themselves.
Putting the result in context
A commonly cited target range used in hormone-panel patient education is roughly 100:1 to 500:1. A ratio below that range is often described as an estrogen-dominant pattern, and a ratio above it as a progesterone-dominant pattern. These are descriptive labels, not diagnostic thresholds — actual reference ranges vary by laboratory, assay method, and specimen type (serum versus saliva), and a single sample says nothing about the trend over time.
When to consult a professional
This calculator performs the standard unit-conversion arithmetic only. It does not diagnose a hormonal condition and does not recommend any treatment or supplementation. Discuss your specific result, your lab's reference range, and your cycle timing with a licensed healthcare provider before drawing any conclusions.