If you know your dog's own rhythm from previous heats, use that — it beats any average.
Estimates based on typical canine cycles (proestrus ≈ days 1–9, estrus ≈ days 10–18, average interval ≈ 6 months). Every dog varies — your vet can confirm the stage with an exam or cytology.
Thinking long-term?
Ask your vet about spaying — it prevents heats, unwanted litters, and reduces the risk of pyometra and some cancers. Pet insurance can help with routine and emergency costs.
How the heat cycle works
A female dog's cycle has four stages. This tool estimates where your dog is based on the date her last heat began.
What the terms mean
- Proestrus (≈ days 1–9) — swelling and bloody discharge; males are interested but she isn't receptive yet.
- Estrus (≈ days 10–18) — the fertile, receptive stage; discharge often lightens. This is the highest-risk window for unwanted pregnancy.
- Diestrus (≈ 2 months) — the quiet hormonal phase after heat, whether or not she's pregnant.
- Anestrus — the resting phase until the next cycle.
How to use it
Mark the first day you noticed bleeding or swelling. During the whole heat — not just the fertile window — keep her leashed outside and fully separated from intact males; sperm can survive several days, so early-heat contact can still lead to pregnancy.
Common questions
My dog's cycle is irregular — is that normal?
Young dogs often take 1–2 years to settle into a rhythm, and small variations are normal. Big changes in an adult dog's pattern are worth mentioning to your vet.
Do dogs go through menopause?
No — intact females cycle for life, though heats may become less regular with age. Pregnancy risks increase in older dogs.
Can I bathe or walk her during heat?
Yes — normal care continues. Just keep walks on-leash and avoid dog parks or any chance of contact with intact males.