PetSums

Dog season calculator

Enter the day your dog's last season started. If you know when the one before it started, add that too and we'll use her own cycle.

The first day you noticed swelling or bleeding.

Leave blank to use the typical 6 to 7 month gap.

Enter the start of her last season and the next dates appear here.

How often dogs come into season

After the first season at around 6 months old, most dogs come into season every 6 to 7 months. Each season lasts about 2 to 4 weeks, and the bleeding part usually lasts a week to 10 days. These are PDSA's figures and they are averages: your dog may run a little shorter or longer, which is why a second date helps.

How this is calculated

With one date, the next season is expected between 182 days (6 months) and 213 days (7 months) after the last one started. Each later season adds the same gap again, so the window widens the further ahead you look. The end date allows for the longest normal season of 4 weeks (28 days) from the latest likely start.

With two dates, the calculator measures the gap between them and repeats it. It only accepts a gap of 3 to 13 months, because anything outside that is more likely to be a typing slip or a missed season than her normal cycle.

Worked example

Pip's last season started on 1 March 2026. Using the typical gap, her next season should start between 30 August and 30 September 2026 and be over by 28 October. Her owner also noted that the season before started on 20 August 2025, a gap of 193 days. Using Pip's own gap, the next season is expected around 10 September 2026.

Things to plan around

Most people use these dates to plan walks away from entire males, book kennels or a dog sitter who knows she's in season, or talk to the vet about when to spay. If she has a season that is very heavy, lasts much longer than four weeks, or she seems unwell, ring your vet.

Questions people ask

How often does a dog come into season?

Most dogs have a season every 6 to 7 months, so about twice a year, according to PDSA. Some dogs keep to their own steady pattern, so once you have two dates logged, the gap between them is a better guide than the average.

How long does a dog season last?

PDSA says a season lasts roughly 2 to 4 weeks, although your dog won't bleed for the whole time. Bleeding usually lasts about a week to 10 days.

When does a puppy have her first season?

Usually at around 6 months old, but it can be as late as two and a half years. Small dogs tend to have their first season earlier than large dogs.

Can my dog get pregnant during her season?

Yes. The season is the fertile part of her cycle. PDSA notes that bleeding is a sign she is at her most fertile, so keep her away from entire males for the whole season, not just while she's bleeding.

Does my dog need a season before she is spayed?

PDSA says the vast majority of dogs do not need a season before spaying. Ask your vet about the right timing for your dog. Once spayed, she stops having seasons.

Sources

  1. PDSA: Seasons in dogs

Figures checked on 25 October 2026. Read how we calculate for the rounding and assumptions behind every tool.