Dog Heat Cycle Calculator

A canine heat cycle calculator is powerful tool for dog owners and breeders to predict when a female dog (bitch) will come into heat.

The calculator typically considers the breed size, the start date of the last heat cycle, and the average length of the dog's cycle to estimate the next heat period.

Let’s say you have a medium-sized dog whose last heat cycle started on January 1st. If her average cycle length is 6 months, the calculator would predict her next heat cycle to begin around July 1st.

Dog Heat Cycle Chart by Breed

Dog Heat Cycle Formula

The formula for calculating a dog’s next heat cycle is:

Next heat start date = Last heat start date + Average cycle length

Typical Cycle Phases and Duration:

Proestrus Phase:

Duration = 7-10 days Signs: Swelling, bleeding

Estrus Phase:

Duration = 5-10 days Fertile period = Usually days 9-14 of total cycle

Diestrus Phase:

Duration = 60-90 days If pregnant: ~63 days

Anestrus Phase:

Duration = 100-150 days Rest period between cycles

Total Cycle Length Formula:

Complete cycle = Proestrus + Estrus + Diestrus + Anestrus
Average = 180-200 days (approximately 6-7 months)

Breeding Window Calculation:

Optimal breeding days = Start of heat + 9 to 14 days

Factors Affecting Cycles:

• Breed Size:
• Small breeds: May cycle 3-4 times/year
• Large breeds: Usually 1-2 times/year
• Age Considerations: First heat = 6-12 months (breed dependent) Senior cycle changes = Around 7+ years
• Pregnancy Planning: Gestation period = ~63 days Optimal breeding age = After 2nd heat cycle

If your medium-sized dog’s last heat started on March 1st, and her average cycle length is 7 months:

Next Heat Start Date = March 1st + 7 months = October 1st (approximately)

This calculation gives you an estimated date to expect the next heat cycle.

How do I calculate my dog’s heat cycle?

To calculate your dog’s heat cycle:

• Record the start date of each heat cycle
• Calculate the time between cycles
• Average these intervals over several cycles
• Use this average to predict future cycles

Let’s say your dog had heat cycles starting on:

• January 1st
• July 15th
• February 1st (the following year)

Calculate the intervals:

January 1st to July 15th: 6.5 months

July 15th to February 1st: 6.5 months

Average: (6.5 + 6.5) ÷ 2 = 6.5 months

You can now predict that your dog’s cycles occur approximately every 6.5 months.

How long is a dog’s heat cycle?

A dog’s heat cycle, also known as estrus, typically lasts between 2-4 weeks. The cycle consists of four stages:

1. Proestrus (7-10 days): The first signs of heat appear
2. Estrus (5-10 days): The fertile period
3. Diestrus (60-90 days): Post-ovulation period
4. Anestrus (4-5 months): Resting period before the next cycle

A Labrador Retriever might have a heat cycle that lasts about 3 weeks total. The first week (proestrus), she may show signs like a swollen vulva and bloody discharge. The second week (estrus) is when she’s fertile and receptive to mating. The third week marks the beginning of diestrus, where these signs start to subside.

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