Cats by 5 months old; dogs between 6 and 15 months, depending on size and sex
The American Animal Hospital Association (AAHA) recommends sterilizing cats by 5 months of age. For dogs, it splits the advice at an expected adult weight of 45 pounds. Small-breed dogs (under 45 lb) are neutered at 6 months if male, or spayed before the first heat, at 5 to 6 months, if female. Large-breed males wait until growth stops, usually between 9 and 15 months, and large-breed females are done somewhere between 5 and 15 months depending on disease risk and lifestyle.
This calculator adds those months to your pet's birthday and turns them into calendar dates. For a cat born on January 31, 2026, the recommended window ends on Tuesday, June 30, 2026, when she turns 5 months old. For a large-breed male dog born the same day, it runs from Saturday, October 31, 2026 to Friday, April 30, 2027. If you enter a surgery date, it also checks whether that date falls inside the window and lists the dates for bathing and activity after surgery.
Why work out spay/neuter timing as dates
"Around five months" or "after six months" is easy to remember but hard to book. A calendar date tells you how long you have left to get an appointment, which matters most for female cats and dogs, since the goal is to act before the first heat.
- You just brought home a kitten: a female can go into heat as early as 4 months, so waiting for the 5-month date can be too late. The calculator shows both the 4-month and 5-month dates.
- You have a small-breed female: the target is before her first heat, so it helps to know the dates for 5 and 6 months and to book a consultation around them.
- You have a large-breed dog: the window is long and it is hard to tell when it starts. For a male the earliest date is 9 months and for a female it is 5 months, and your vet narrows it down by how your dog is growing.
- You already picked a surgery date: for about two weeks afterward your pet should not run or jump and should not be bathed. Check that the dates don't collide with a trip, a move or a holiday.
How the calculation works
- Pick the recommendation: choose one of five cases from the species, the sex and, for dogs, the expected adult weight (see the table below). Cats follow the same advice whatever they weigh.
- Turn it into a date: add the recommended months to the birthday. If that month has no matching day, the last day of the month is used. A birthday of January 31 plus 5 months is June 30, and a birthday of February 29, 2024 plus 12 months is February 28, 2025.
- Compare with today: before the window, it counts the days until it starts (for cats and small-breed males, until the target date). Inside the window, it counts the days until it ends. After the window, it counts the days since.
- If you enter an age: when you don't know the birthday, enter the current age in months. The calculator counts back from today to estimate a birthday, so the dates are approximate.
- Surgery schedule: enter a surgery date and it judges the age on that day against the window, then adds the day before, stitch removal at 7 to 14 days, bathing at 10 days and the end of activity limits at 14 days.
Basis Recommended date = birthday + recommended months (the last day of the month if the day doesn't exist) · Days left = recommended date − today · The AAHA owner guidance (revised 2026-02-05), ASPCA and VCA (updated 2025-09-18) pages were checked on 2026-10-17.
Recommended timing by species, size and sex, with example dates
The dates are for a pet born on January 31, 2026. A dog with an expected adult weight under 45 lb (about 20.4 kg) counts as small-breed, and a heavier one as large-breed.
| Case | AAHA recommendation | Born 2026-01-31 |
|---|---|---|
| Cat (either sex) | By 5 months old | By 2026-06-30 (Tue) |
| Small-breed male | 6 months old | 2026-07-31 (Fri) |
| Small-breed female | Before first heat, 5 to 6 months old | 2026-06-30 (Tue) – 2026-07-31 (Fri) |
| Large-breed male | After growth stops, usually 9 to 15 months old | 2026-10-31 (Sat) – 2027-04-30 (Fri) |
| Large-breed female | 5 to 15 months old, depending on disease risk and lifestyle | 2026-06-30 (Tue) – 2027-04-30 (Fri) |
The ASPCA says healthy puppies and kittens as young as eight weeks old can be spayed or neutered. That is why the cat bar on the calculator's map starts at 8 weeks (March 28, 2026 for a cat born January 31, 2026). Large-breed dogs are different: AAHA advises waiting until growth stops, so 8 weeks is not used as a starting point for them.
Female cats: watch for a first heat from 4 months
AAHA notes that female kittens may enter their first heat cycle as young as four months, but usually not until they are five or six months old. The ASPCA likewise advises scheduling the surgery before a cat reaches five months of age. For a female born on January 31, 2026, a first heat could start as early as Sunday, May 31, 2026, so it is safer to have a consultation booked before that date. On the calculator's map, the 4-to-6-month stretch is hatched.
If your cat has already been in heat, or might be pregnant, the timing and the method of surgery can change. Tell the clinic when you book.
If you don't know your dog's adult weight
The dividing line is the weight your dog is expected to reach as an adult, not the weight today. For a purebred, use the breed standard; for a mixed breed, look at the size of the parents, and when it is unclear your vet can judge from how fast your dog is growing. The table gives weights from the American Kennel Club (AKC) breed pages.
| Breed | AKC standard weight | On this calculator |
|---|---|---|
| Maltese | Under 7 lb | Small |
| Toy Poodle | 4–6 lb | Small |
| Pomeranian | 3–7 lb | Small |
| Shih Tzu | 9–16 lb | Small |
| Bichon Frise | 12–18 lb | Small |
| Pembroke Welsh Corgi | Male up to 30 lb Female up to 28 lb | Small |
| Shiba Inu | Male 23 lb Female 17 lb | Small |
| Border Collie | 30–55 lb | Straddles the line |
| Siberian Husky | Male 45–60 lb Female 35–50 lb | Male: large Female: straddles the line |
| Golden Retriever | Male 65–75 lb Female 55–65 lb | Large |
| Labrador Retriever | Male 65–80 lb Female 55–70 lb | Large |
For breeds whose standard range crosses 45 lb, such as a Border Collie or a female Husky, ask your vet whether the small-breed or large-breed window fits better. You can switch between the two on the calculator and see right away how much the dates differ.
Once you have a surgery date: the day before through two weeks after
The ASPCA says that for adult dogs and cats the usual instruction is no food after midnight the night before, but a puppy or kitten needs nutrition and the vet may advise not withholding food. That is why the calculator puts no clock time on the day before and tells you to follow your clinic's instructions.
- Running and jumping: prevent them for up to two weeks after surgery, or as long as your vet recommends (ASPCA).
- Bathing: avoid it for at least ten days after surgery (ASPCA).
- Licking the incision: use a properly fitted Elizabethan collar (cone) so your pet can't lick it (ASPCA).
- Stitches: most skin stitches are removed 7 to 14 days after the operation, and the timing depends on the type of surgery (VCA Animal Hospitals).
For example, with surgery on Friday, June 12, 2026, the day before is Thursday, June 11, stitch removal or a recheck falls between Friday, June 19 and Friday, June 26, bathing can resume on Monday, June 22, and the running and jumping limit ends on Friday, June 26. If the incision opens, swells or oozes, or your pet seems lethargic or won't eat, call the clinic that did the surgery right away.
In the US: the cat guideline and who sets the rules
AAHA is a US organization, and it endorses the "Fix Felines by Five" initiative, which recommends sterilizing cats by five months of age. This calculator's cat result is that same guideline. AAHA's recommendations are for veterinarians and owners to follow, not a law, and the calculator doesn't treat them as one.
Prices differ from clinic to clinic, and requirements differ by state, county and city, so this page gives no figures or local rules. Ask nearby clinics for a written estimate, and ask your city or county animal services what applies where you live.
Common mistakes
- Choosing the size by today's weight: a 3-month-old Golden Retriever is still small. What counts is the expected adult weight.
- Treating the 5-month date as the day to start: for cats, 5 months is the deadline, not the start. Book the consultation and the appointment before it.
- Thinking it is too late once the window has passed: the window describes the best time, not the only time. If it has passed, have your vet check your pet's health and set a date.
- Using the adult fasting rule for a puppy or kitten: young animals may be told not to fast. Follow the times your clinic gives you.
- Reading "5 to 15 months" for a large-breed female as "wait until 15 months": it means your vet picks a date inside that range, based on her disease risk and lifestyle.
Limits and cautions
- The recommended months come from AAHA and the ASPCA. They don't replace your clinic's own policies, scheduling or anesthesia standards.
- The calculator can't tell whether your pet is fit for surgery. Your vet sets the actual date after looking at health, breed, heat cycles, possible pregnancy and pre-anesthetic tests.
- If you enter an age, the birthday is estimated by counting back from today, so the dates can be off by a few weeks from the real ones.
- Dates are compared with today's calendar date on your device, with no time of day. Nothing you enter is sent to a server.
Sources
- 01AAHA: When Should I Spay or Neuter My Dog or Cat?Posted 2019-06-21, revised 2026-02-05. Cats by five months (Fix Felines by Five); a female kitten's first heat as early as four months, usually five or six; small-breed dogs (projected adult weight under 45 lb) neutered at six months or spayed before the first heat (five to six months); large-breed males after growth stops, usually 9 to 15 months; large-breed females 5 to 15 months depending on disease risk and lifestyle (checked 2026-10-17)
- 02AAHA 2019 Canine Life Stage Guidelines: Spay and Neuter TimingTable of timing by size and sex (small male 6 months, small female 5 to 6 months before the expected heat, large male 9 to 15 months, large female 5 to 15 months)
- 03ASPCA: Spay/Neuter Your PetHealthy puppies and kittens as young as eight weeks; schedule a cat's surgery before five months; adults take no food after midnight the night before (young animals may differ); no running or jumping for up to two weeks; no bath for at least ten days; Elizabethan collar
- 04VCA Animal Hospitals: Post-Operative Instructions in DogsUpdated 2025-09-18. Most skin stitches are removed 7 to 14 days after the operation, depending on the type of surgery
- 05American Kennel Club: Dog BreedsStandard weight for each breed in the table above (see each breed's link)
Frequently asked questions
When should I spay or neuter my cat?
The American Animal Hospital Association (AAHA) recommends sterilizing cats by 5 months of age. The ASPCA says healthy kittens as young as eight weeks old can be spayed or neutered and advises scheduling the surgery before a cat reaches five months. For a kitten born January 31, 2026, that is by June 30, 2026.
When should I spay or neuter my dog?
It depends on the expected adult weight, with the line at 45 pounds (about 20.4 kg). AAHA recommends 6 months for small-breed males, 5 to 6 months (before the first heat) for small-breed females, usually 9 to 15 months (after growth stops) for large-breed males, and 5 to 15 months for large-breed females depending on disease risk and lifestyle.
What if I don't know my dog's adult weight?
Go by the weight your dog is expected to reach as an adult, not today's weight. Use the breed standard for a purebred and the parents' size for a mixed breed. By AKC standards a Maltese, Toy Poodle, Shih Tzu or Shiba Inu is small, and Golden and Labrador Retrievers are large. If your dog straddles the line, like a Border Collie (30–55 lb) or a female Husky (35–50 lb), let your vet decide.
Is it too late if the recommended window has passed?
No. The window describes the best time, not the only time. If it has passed, have your vet check your pet's health and set a date. The calculator shows how many days have gone by but cannot tell whether your pet is fit for surgery.
My female kitten is 4 months old. Should I hurry?
AAHA says female kittens may have a first heat as early as four months but usually not until five or six months. Once she is past 4 months a heat is possible, so book a consultation soon, and tell the clinic if she has already been in heat or might be pregnant.
When can my pet have a bath or go for a run after surgery?
The ASPCA says to avoid bathing for at least ten days and to prevent running and jumping for up to two weeks, or as long as your vet recommends. VCA Animal Hospitals says most skin stitches come out 7 to 14 days after surgery. Follow the instructions of the clinic that did the operation.
Does the US have a law on when to spay or neuter?
AAHA, a US veterinary organization, endorses the Fix Felines by Five initiative and recommends sterilizing cats by five months, but that is a recommendation, not a law. Requirements differ by state, county and city and are not covered here, so ask your local animal services what applies where you live.
How much does spaying or neutering cost, and what should I ask the clinic?
Prices vary by clinic and region, and no figures are given here. Ask for a written estimate and check whether it includes pre-surgery bloodwork, anesthesia, pain medication, an e-collar and a stitch-removal recheck, and whether extra charges apply for a pet in heat, an undescended testicle or obesity.