What a Dog Progesterone Calculator Actually Does
Last Reviewed: June 19, 2026. Educational tool. Not veterinary advice.
Most "progesterone calculator" searches come from breeders staring at one number and trying to figure out what it means in context. The honest answer is that one number means little. The trend across two or three readings means almost everything.
Looking for the actual tool? The interactive tracker lives one click away.
Open the Free Progesterone Tracker →The P4 Benchmarks Every Breeder Hears
These are textbook averages. Individual dams vary. Lab assays vary. Always confirm calibration against the lab running the test and defer to your reproductive vet on what each number means for your specific dam.
Under 2 ng/mL — Pre-LH Proestrus
Visible heat is underway but the LH surge has not happened yet. Eggs are not mature. Breeding here will not produce a pregnancy. Useful for confirming you are in the cycle but not at the window.
2 to 3 ng/mL — LH Surge Imminent
The LH surge typically happens around 2 ng/mL. Some labs and some dams trigger the surge slightly earlier or later. This is the "test daily now" zone. Missing the surge is the difference between a confirmed and a guessed ovulation date.
Around 5 ng/mL — Ovulation
Ovulation occurs roughly 48 hours after the LH surge, when progesterone reaches about 5 ng/mL. This is the reference point for breeding date math. Whelping is 63 days from ovulation, give or take a day.
8 to 30 ng/mL — Fertilization Window
Eggs mature for about 48 hours after ovulation, then remain viable for another 48 to 72 hours. Natural cover and chilled breedings target this window. Frozen breedings target the tighter end of it.
Over 30 ng/mL — Past Peak
The fertilization window has closed. If you missed it this cycle, the next opportunity is the next heat. Logging this end-of-window number is useful for refining timing on the next cycle.
What a Progesterone Calculator Cannot Do
Tell You When to Actually Breed
The tracker shows where the dam is. Your reproductive vet decides when to breed based on the breeding method (natural, chilled, frozen), the stud's semen quality, and how the dam's surge is progressing. The tool gives the vet organized data, not the answer.
Run the Test
Lab-grade quantitative P4 testing still happens at a vet clinic. Cage-side semi-quantitative tests exist but accuracy varies. The tracker handles whatever number you put in; the test happens upstream of it.
Compensate for Bad Timing on Earlier Readings
If you tested every four days through the surge instead of every 24 to 48 hours, the trend is going to skip over the LH surge entirely. The tracker shows what happened; it cannot reconstruct what was missed.