Hey I’m a closeted trans girl, I’m 16 and I’m from the UK. Recently I’ve been trying to express my gender identity a bit more by growing my hair out, however whenever it gets more than about 4 inches long my parents force me to have it cut short. I don’t know if they’re legally allowed to force me to cut my hair, in my opinion I don’t think anybody should have the right to dictate anybody’s appearance but I really want to grow it out. At the moment my hair is about 3-4 inches on the top and about 1.5 inches in the back and sides. I wear it slicked back and to the side so it looks shorter and neater to them, so they won’t cut it. Any advice on what to do would be really awesome. Thanks.
Offer to pay for your haircut when you want one (though for healthy tips a short trim every 2 months) and then it isn't their loss. That's if money is a concern or anything.
Why can't a guy have long hair? Plenty of guys have long hair. Promise them that you will take care of the hair and use conditioner, and you should look fine and neat if this is their concern.
I had the opposite problem with my parents. They hated it when I got my hair cut short and insisted I have long hair. After I came out I was forbidden from getting a hair cut. My way around that was that I cut my hair in secret, and never let it grow longer than shoulder length. That let me have a more androgynous look that was bearable to me, and satisfied my parents' demands. For you, I would recommend doing what emerry said. Grow it out, promise to take care of it, and offer to pay for your own haircuts so they will get off your back. There are plenty of guys with long hair, so use them as an example for your parents. I remember whenever I'd get my hair cut, I would show my parents an example of a girl with short hair so they wouldn't think I was getting a "men's cut." You can show your parents pictures of men with shoulder length hair and say you want something like that. Try to get an androgynous style when you go to get it cut, so you have more room for styling it in a feminine way if you like. If you absolutely have to get it cut, you could invest in some wigs to wear in private. I would sometimes put all my hair up into a hat and dress in a tie secretly. I'd take some photos, and feel good in that moment while I could. Then I'd take it all off, hide it away, and dress the way my parents wanted me to publicly. One day you will be able to have your hair however you like, so remember that. As soon as I moved out of my parents home I had all my hair chopped off and it was one of the happiest days of my life.
You're 16. I think 16 is a perfect age to practice setting reasonable boundaries with your parents, or anyone else for that matter. Bear in mind that you still have a couple of years left before legally everything is up to you. Bodily autonomy and security is important for everyone; male, female, cis, trans, young, old etc. I know it's just hair but technically it's part of your body. No one, not even a parent has a right to tell you what you can or can't do with your own body (as long as you aren't hurting anyone else.) You are legally entitled to not have other people touch any part of your body (including your hair) if you don't want them to and don't consent to it.
The simple answer is that no, they can't physically force you to get your hair cut. However, while you are still living under their roof and financially dependent on them it's not necessarily that simple as they have power over your life in other ways. I don't know what kind of relationship you have with them but are you able to have a mature, reasoned discussion about how important it is to you, what their exact issue is with your hair and how you can help them feel more comfortable with it? I'm tempted to say "just tell them you're not cutting it and that's that" but don't want to make your life difficult in other ways in terms of your relationship with them.