Biology

Dog Heat Cycle Calculator

Track a dog's heat (estrus) cycle stage.

Calculated Output

Current stage Proestrus (not yet fertile)

Days to next cycle 175

Formula: proestrus 0–9 d, estrus (fertile) 9–18 d, then diestrus

Step-by-Step Breakdown

1. Values used:

2. Days since heat started = 5 days

3. Months between cycles = 6

5. Current stage = Proestrus (not yet fertile)

6. Days to next cycle = 175

Did this calculator solve your problem today?

The math behind it

Proestrus lasts ~9 days, estrus (the fertile window) ~days 9–18, then diestrus. Most dogs cycle about every 6 months.

Day 5 → proestrus; fertility begins around day 9.

Breeding?

Confirm the fertile window with your vet via progesterone testing.