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.
A female dog's cycle has four phases: proestrus (swelling and bleeding, about 9 days), estrus (the receptive phase, about 9 more days), diestrus(roughly two months of high progesterone whether or not she's pregnant), and anestrus (the resting phase that sets her interval). The interval between heats is the part that varies — about 6 months on average, but anywhere from 4 to 12 months can be normal for an individual dog.
That's why this calculator asks for two heat dates if you have them: her own measured interval predicts her next heat far better than any breed average. With one date it uses the interval you select and shows a wider window to stay honest.
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.
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.
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