How can you tell if you are a boy or a girl, or something else entirely?

It's how you feel inside, regardless of what people think you are. Look at yourself. Be yourself. What do you think you are?

Gender is really all in your head. If you identify as a boy or girl, you are a boy or girl. If you feel like you don't identify with either, you might be a different gender, be a mix of genders, or have no gender.

Based on personal experience, it depends pretty much entirely on how I'm feeling on any particular day, this is what they call Gender fluidity. Seeing as I spend every day identifying what gender I am, I guess I could be qualified to answer. Usually my clothing represent my gender, or just my general attitude. When I first get up in the morning is the time that I take time to identify, whatever you're yearning for in the morning is a helpful signifier as to your gender. This may not work for everyone, like I said, this is only how I happen to identify and do it myself. Like sometimes if I am identifying as a female, in the morning the first thing I want to do is wash my face, pick out some clothes and do a little bit of makeup, whereas usually when I identify as male I really want to eat and just start gaming or surfing the web. When I identify as genderless its a bit more complicated, I usually don't recognise it at first, I just do whatever I want, I don't feel the need to conform to a gender norm at the time. So I guess just paying attention to how you feel in the morning especially, seeing what you gravitate towards, what you really want, is a helpful way to identify. Hopefully someone finds this helpful.

This isn't something you can take an online quiz for. This is something you feel. Gender is a spectrum. It is what you want to be identified as. What pronouns you want people to refer to you. He/she/they/etc. Now gender expression is a different story. It is also a spectrum which goes from masculine to androgynous to feminine. You could be a boy who loves dresses but still wants to be referred to as a boy. Or vice versa. You could be neither gender and rather dress androgynous-like. That's all okay. You know you best. However you decide to express yourself is on you. No one should tell you how to dress/define YOUR body.

You can tell your a boy/girl/else when you feel you are in your mind, emotion and everyday life it may take time to realize you feel this way or you may know from when you we're little.

To me, I feel that I can identify my own gender based on what I am most comfortable being when I look inside my mind and my heart.

Nobody but yourself can tell you exactly what your gender identity is, and it may take you a while to figure out an identity that you feel that you fit with. There are a load of super helpful resources out there that can assist you if you're questioning your gender identity, such as gendercentre.org.au (an Australian based organisation aiming to help transgender and gender questioning individuals). Just remember, you aren't required to fit any labels if you don't want to, and your experiences are completely valid no matter what negativity might come your way.

by the way that you feel. just because you look male or female or have the body of either gender does not mean you are supposed to be that way. it's entirely based on how you feel

It's about looking inside of your own heart. This is YOUR life to live, and as long as you are happy, healthy and enjoying life - what you are is just a title for the entire being.

Usually genitalia is the main source to identify your gender. However this does not fit for everybody, since genitalia does not automatically means gender. Do some research on transexual persons and those who have disorders of sexual development. At the end of the day what matters most is the person not the label we put on.