Track your female dog's estrus (heat) cycle stages, predict the next heat, and identify optimal breeding windows. Includes cycle timeline, signs, and management tips.
The canine estrous cycle has four distinct stages — proestrus, estrus, diestrus, and anestrus — with the entire cycle averaging 6-7 months. Most unspayed female dogs experience their first heat between 6-12 months of age, with smaller breeds cycling earlier and large/giant breeds sometimes not until 18-24 months.
Understanding your dog's heat cycle is important whether you're planning to breed or simply want to manage and protect your intact female. Proestrus lasts about 9 days (range 3-17), during which you'll notice vulvar swelling and bloody discharge. Estrus (the fertile period) lasts about 9 days, during which discharge lightens and the female becomes receptive to males.
This calculator helps you track cycle stages, predict upcoming heats, identify the fertile window for breeding purposes, and provide management recommendations for each stage. Accurate cycle tracking over 2-3 heats helps establish your dog's individual pattern for better prediction. Better timing data reduces stress, improves breeding decisions, and helps avoid preventable scheduling errors.
For best results, combine calculator output with direct observation and periodic check-ins with a veterinarian or qualified advisor. Small adjustments made early usually improve comfort, safety, and long-term outcomes more than large corrective changes made later.
Tracking your dog's estrous cycle enables better management — whether preventing unwanted pregnancy, timing a planned breeding, or scheduling spay surgery. Over multiple cycles, this calculator helps establish your dog's individual pattern for more accurate prediction. This dog heat cycle calculator helps you compare outcomes quickly and reduce avoidable mistakes when making day-to-day care decisions. Use the estimate as a planning baseline and confirm final decisions with a qualified professional when risk is high.
Estrous Cycle: Proestrus (~9 days) + Estrus (~9 days) + Diestrus (~60 days) + Anestrus (variable: 4.5-10 months). Inter-estrous Interval: Small breeds: ~5-7 months, Medium: ~6-7 months, Large: ~7-8 months, Giant: ~8-12 months. Fertile Window: Days 9-14 from onset of proestrus (most dogs). Ovulation: ~48 hours after LH surge, typically Day 12.
Result: Currently in proestrus (Day 5). Estrus expected ~Jan 24. Fertile window: Jan 23-30. Next heat: ~July-August 2026.
For a medium-sized dog on her 3rd heat with onset January 15, proestrus should last about 9 days. Estrus begins around January 24, with the fertile window spanning approximately January 23-30. The next heat cycle is predicted at approximately 6.5 months later.
**Proestrus (7-10 days):** Estrogen rises, vulva swells, bloody vaginal discharge appears. Males are attracted but the female rejects mounting. Behavioral changes include restlessness, frequent urination, and tail tucking when approached by males.
**Estrus (7-10 days):** Progesterone rises, discharge becomes lighter/straw-colored, vulva softens. The female becomes receptive — she'll "flag" (hold tail to side) for males. Ovulation occurs 24-48 hours after the LH surge, typically 2-3 days into estrus.
**Diestrus (60-90 days):** Whether or not mating occurred, high progesterone maintains the uterus for potential pregnancy. If pregnant, whelping occurs around day 63. If not pregnant, the body slowly returns to baseline. False pregnancy is common.
**Anestrus (4-10 months):** Reproductive rest phase. The uterus recovers and hormones return to baseline levels. This is the ideal time for elective spay surgery.
Natural breeding or artificial insemination is most successful when timed to ovulation. The LH surge can be detected by daily blood testing during estrus. Ovulation occurs 48 hours after the LH surge, and eggs need 48 hours to mature — so the optimal breeding window is 4-6 days after the LH surge. A single well-timed breeding has conception rates above 80%.
Most dogs cycle every 6-7 months (twice yearly). Small breeds may cycle every 5-6 months, while giant breeds may cycle every 8-12 months or even only once per year.
The active heat (proestrus + estrus) lasts about 2-3 weeks. The complete estrous cycle including hormonal changes spans 6-7 months. The visible signs (swelling, discharge) typically resolve within 21-28 days.
Most dogs are most fertile during days 9-14 of the cycle (counting from first signs of proestrus). Ovulation typically occurs around day 12. Progesterone blood tests provide the most accurate timing for breeding.
Small breeds: 6-9 months. Medium breeds: 8-12 months. Large breeds: 10-15 months. Giant breeds: 12-24 months. The first heat may be irregular or "silent" (few visible signs).
Yes, but use a leash at all times and avoid dog parks or areas with intact males. The scent of a female in heat can attract males from great distances. Keep walks shorter and to familiar routes.
No — unlike humans, dogs continue to cycle throughout their entire lives. However, cycles may become irregular, less frequent, and less fertile with age. Older unspayed dogs have increased risk of pyometra (uterine infection) with each cycle.