How to Calculate Dog Heat Cycle
What is Dog Heat Cycle?
Female dogs cycle typically every 6 months. The fertile window (oestrus) is approximately days 9–14. Understanding the cycle helps with breeding or prevention.
Formula
Estrous cycle: 21 days typical (range 14–42). Proestrus 7–10 days (swelling, discharge). Estrus 3–14 days (receptive, fertile window). Diestrus 60 days (progesterone peak). Anestrus 120–150 days (rest)
- CycleStart
- First day of heat (proestrus) (Date)
- CycleDays
- Cycle length (Days (typical 21))
- FertileWindow
- Peak fertility window (Days 5–14 of cycle approximately)
Step-by-Step Guide
- 1Proestrus (days 1–9): bloody discharge; not receptive
- 2Oestrus (days 9–14): receptive; fertile window
- 3Progesterone testing gives most accurate ovulation timing
- 4Average cycle interval: 6 months (range 4–12 months)
Worked Examples
Input
Cycle started 1 March
Result
Fertile window approx 9–14 March; next cycle approx September
Frequently Asked Questions
How often do dogs go into heat?
Usually twice yearly (every 6 months), but ranges 4–12 months normal. Smaller breeds more frequent. Larger breeds less frequent. Nursing, illness can delay cycles.
When can a dog get pregnant?
During estrus (proestrus day 7–10 typically). Fertile window 48 hrs around LH surge (behavioral: standing to mate). Sperm live 7 days in female tract; egg 24–48 hours.
What signs indicate heat?
Swollen vulva, bloody discharge, increased urination, behavioral changes (restlessness, nervousness). Some breeds discharge less visible. Smell test: males attracted from distance.
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