Estrogen to Progesterone Ratio Calculator
The ratio between progesterone and estrogen (estradiol) says more about hormone balance than either number alone — both values can sit 'in range' while the balance between them is off. Enter the two values from your lab report (saliva, serum, or blood spot) in the same units, and get your ratio in both directions with reference context.
Progesterone ÷ estradiol (Pg/E2)
Use the units printed on your report — the ratio is unit-free as long as both inputs match
Same units as progesterone (e.g. both pg/mL)
Enter your value above to see the result.
Estradiol ÷ progesterone (E2/Pg)
Same units as progesterone
Use the units printed on your report
Enter your value above to see the result.
This result is a screening estimate, not a diagnosis. Discuss your labs with a qualified healthcare professional.
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How it works
The formula
Pg/E2 ratio = progesterone ÷ estradiol, with both values in the same units (e.g. pg/mL ÷ pg/mL). The inverse (E2/Pg) is the same division flipped. Because the units cancel, the ratio works for saliva, serum, or blood-spot reports — as long as you don't mix units between the two inputs.
Why the ratio, not the individual numbers
Progesterone and estradiol each have wide reference ranges, and both can fall 'in range' while the balance between them is off. Functional-medicine labs popularized the Pg/E2 ratio precisely because symptoms often track the balance rather than either absolute value.
Where the 100–500 window comes from
The commonly quoted Pg/E2 reference window (roughly 100–500 for a luteal-phase saliva sample) originates from functional-medicine lab cohorts, notably ZRT Laboratory's saliva testing literature. These are research-cohort conventions, not official guideline cut-offs — serum ranges differ, and every lab prints its own reference interval.
Limitations
The ratio shifts across the cycle (it is only meaningful against the phase you tested in — usually mid-luteal, around days 19–21 of a 28-day cycle), and across assay methods (saliva, serum, and dried urine are not interchangeable). One measurement is a snapshot; trends and symptoms, reviewed with a qualified practitioner, carry the real meaning.
Frequently asked questions
What should my progesterone to estrogen ratio be?
For a mid-luteal saliva sample, functional-medicine labs commonly describe a Pg/E2 ratio of roughly 100–500 as balanced. Serum testing uses different ranges, so always compare against the reference interval on your own report. These figures are research-cohort conventions, not official guideline cut-offs.
How do I calculate the estrogen to progesterone ratio?
Divide one hormone value by the other using the same units: progesterone ÷ estradiol gives the Pg/E2 ratio (the most common form), estradiol ÷ progesterone gives the inverse. This calculator runs both directions instantly from the numbers on your lab report.
Which sample type should I use — saliva, serum, or dried urine?
Use whichever report you already have, but don't mix methods or units between the two inputs, and know that reference windows differ by method: the 100–500 window comes from saliva testing. DUTCH (dried urine) reports metabolites rather than the parent hormones directly — read the ratio guidance printed on that report first.
When in my cycle should I test?
The ratio is usually interpreted from a mid-luteal sample — around days 19–21 of a 28-day cycle, when progesterone peaks. A follicular-phase or random-day result will sit far outside the luteal reference window without anything being wrong. If your cycle is irregular or absent, interpretation needs a practitioner's help.
What does a low Pg/E2 ratio mean?
A ratio below the common window is described in functional-medicine literature as an estrogen-dominant pattern — relatively more estradiol activity than progesterone. It is a screening signal, not a diagnosis: it can reflect cycle timing, perimenopause, supplementation, or assay choice, and it's best reviewed alongside your symptoms with a qualified practitioner.
How is this different from the FSH LH ratio?
They measure different axes. The estrogen/progesterone ratio looks at ovarian output hormones (often from saliva or DUTCH testing), while the FSH LH ratio looks at the pituitary signals that drive the ovaries, from a day-3 blood draw. Both are ratio views — see our FSH LH Ratio Calculator for the other one.
Sources
- Zava DT, ZRT Laboratory. Salivary progesterone/estradiol (Pg/E2) ratio — reference ranges and technical literature.
- Stanczyk FZ, Clarke NJ. Advantages and challenges of mass spectrometry assays for steroid hormones. J Steroid Biochem Mol Biol, 2010.
This calculator is for informational purposes only and is not medical advice, diagnosis, or treatment. Reference ranges are general population guidelines — always discuss your lab results with a qualified healthcare professional.