Dog Heat Cycle Calculator

Predict when your female dog's next heat will start and find her most fertile window for planned breeding.

988.3K uses Updated · 2026-05-12 Runs locally · zero upload
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How to Use Dog Heat Cycle Calculator

The Dog Heat Cycle Calculator helps you project the next heat cycle and reminder date from a single previous start date.

  1. Enter the last heat start date — Use the first day you noticed bleeding or swelling.
  2. Pick the dog’s size — Size determines the typical cycle interval.
  3. Adjust the cycle interval if needed — Override the default if your dog has historically cycled faster or slower.
  4. Set a reminder lead time — Get a heads-up before the next heat for planning purposes.

Formula & Theory — Dog Heat Cycle Calculator

Most female dogs cycle 1–2 times per year. The fertile window typically falls 9–14 days after onset:

next_heat = last_heat + cycle_months × 30 days
fertile_window = [last_heat + 9, last_heat + 14]
remind_on = next_heat − reminder_days

Use Cases for Dog Heat Cycle Calculator

Planning a litter, avoiding accidental breeding, scheduling spay surgery between heats, or tracking irregular cycles.

The Dog Heat Cycle Calculator is a quick reference, not a substitute for veterinary advice. Always cross-check with a vet, especially for medication or toxicity questions.

Frequently asked questions about Dog Heat Cycle Calculator

When is my dog most fertile?

For most dogs, the optimal mating window is days 9 to 14 after the start of bleeding. Vets confirm with progesterone testing.

Are heat cycles always regular?

No — young dogs often have erratic cycles. Three consistent cycles are needed before the interval is considered stable.

Can I spay during heat?

It is safer to wait 2–3 months after a heat to reduce bleeding risk during surgery.

Why do giant breeds cycle less often?

Larger breeds reach sexual maturity later and have hormonal patterns that favor longer intervals between cycles.

Is my data stored?

No. All calculations happen in your browser; nothing is sent to a server.