Enter the first day of her last heat and get her next expected heat, an honest ± window, and her likely fertile days — the same prediction engine breeders use inside Whelpify.
Enter the first day of her most recent heat and we'll project her next heat, the realistic window around it, and her likely fertile days.
The phases themselves are remarkably consistent — it's the resting interval between heats that varies from dog to dog, which is why her own recorded dates beat any breed average.
Vulvar swelling and bloody discharge. She attracts males but is not receptive yet.
The receptive phase. Ovulation happens here — the typical fertile window is days 10–14.
Progesterone stays high whether or not she is pregnant. False pregnancy signs can appear.
The resting phase that sets her interval — 6 months on average, 4 to 12 can be normal.
Schedule serial testing with your repro vet for 2–3 days after the heat starts — the prediction puts it on the calendar early.
Chilled semen shipments and stud schedules are far easier to arrange with a heads-up than a same-week scramble.
A predicted breeding is when serious breeders start collecting applications — not after the puppies arrive.
Most females cycle roughly every 6 months, but the normal range is wide — from about every 4 months in some small breeds to once a year in some giant breeds. An individual dog is far more consistent with herself than with the breed average, which is why tracking her own dates beats any rule of thumb.
A full heat typically runs 2–3 weeks: proestrus (swelling and bleeding, roughly days 1–9) followed by estrus (the receptive phase, roughly days 9–18). Both phases vary by several days between dogs.
The typical fertile window falls around days 10–14 from the first day of the heat, but ovulation timing varies enough that calendar counting alone regularly misses breedings. Serial progesterone testing through your veterinarian or a reproduction clinic is the only reliable way to time a breeding or an insemination.
As accurate as heat prediction can honestly be: it projects from her last heat using either her own measured interval (if you enter two dates) or the interval you choose, and it always shows a ± window instead of a fake-precise date. Cycles naturally drift, especially in young dogs and seniors.
The numbers behind this calculator come from veterinary literature and clinical references, not folklore:
Record each heat once and Whelpify learns her real interval, predicts the next one, and emails you two weeks before — plus waitlists, applications, and a website that fills the litter before go-home day.
Calculate when the puppies are due from the ovulation date, LH surge, or breeding date — plus a pregnancy timeline with ultrasound and X-ray windows.
Open the calculator From birth to go-home day, mapped out.Enter a litter’s birth date and get the full development timeline: eyes opening, weaning, first vaccines, socialization windows, and go-home day.
Open the calculator How big will this puppy get?Estimate a puppy's adult weight from their current age and weight using size-class growth curves — with an honest range, plus when they'll finish growing.
Open the calculatorSet up your whole system in minutes — from litters and puppies to payments and applications. Try everything free for 30 days, then choose monthly or yearly billing.
30 days free. Cancel anytime before the trial ends and pay nothing.