How to tell if my cat is a boy or a girl after a month?

From this photo, this appears to be a male kitten. You can read more about determining kitten gender at https://www.vetmed.wsu.edu/outreach/Pet-Health-Topics/categories/procedures/cats/determining-gender-(sex)-of-a-kitten

She's cute. She looks to be around 4-5 months of age, but you should weigh her. Her weight in months +1 is usually how we guess kittens ages. You should look at this photo to determine if this kitten is male or female. At this age it should be noticeable testicles and a penis protruding right below it if kitty is a male. https://www.vetmed.wsu.edu/outreach/Pet-Health-Topics/categories/procedures/cats/determining-gender-(sex)-of-a-kitten Best wishes with your new kitty! Take care.

I would guess this is a female but it can be a little difficult to tell from a picture. This might help you figure it out at home: https://www.google.com/amp/s/mobile.petcoach.co/amp/article/sexing-kittens

The general rule of thumb is about 1 month of age for each pound of weight. This is not accurate in all cases though. Baby teeth, incisors and canines (fangs), erupt at about 3-4 weeks of age. If Lucy has all her baby teeth, she is at least 6 weeks old. You should be able to determine sex right away. This is how: Lift the tail. Right under the tail is the anus. Below that is another opening which is round in males and a vertical slit in females. Also, the distance between the anus and genital opening is greater in males. A physical exam by your vet can confirm gender. You can also post a clear picture of the back end in a new question and we can let you know.

From the pictures, it looks as though the names Bonnie and Clyde are appropriate! :-) The first kitten (photo on the left) appears to be male and the second kitten (photo on the right) appears to be female. I still recommend asking your vet to confirm their genders at their first appointment since photos can occasionally be misleading.

Based on the distance between Comet's anus and genitals, I agree that he appears to be male. The picture is quite blurry when I try to zoom in, but it appears that from the top down, you can see his anus, scrotum, then penile opening (the penis itself is contained inside of this prepuce). I would expect more of a vertical opening for the vulva without anything above it in a female. I've included an article that has a rudimentary drawing that's pretty helpful. This is unrelated, but I also see rice-like particles on Comet's hind end. These appear to be tapeworm segments, which can be acquired by eating either tapeworm infected fleas or rodents. I'd recommend asking Comet's vet about deworming him for tapeworms based on this picture. https://www.petcoach.co/article/sexing-kittens/

From the attached picture it appears to be a neutered male - likely one that was neutered at a young age as I do not see the presence of a well developed scrotum. If you want, you can post another picture - including some of the tail all of the anus and everything below the anus. If you look at the part below the anus (this is either a vulva or a penis in a sheath) - you may be able to tell better yourself. Thank you for using pet coach!