how old do you have to be to be able to ejaculate?!

Usually around 12 or 13, but sometimes later. The funny thing is that it is a functional thing, meaning that it depends on the conditions of your life. For example, if you grew up in a stressed situation/life (like, you might not live very long because of your surroundings), your body might produce testosterone faster, and you would become capable of reproduction earlier. There are other factors, too, so it's really a grey area.

Masturbation around 8 or 10 is completely normal with no ejaculate.

My aunt studied medicine and I would frequently read some of her books.

One of the earliest indications of puberty is the testicles enlarging. Usually the capability to ejaculate semen comes about one to two years after puberty starts -- often about the time pubic hair begins to grow and a boy begins his growth spurt. The average age for starting puberty is 11 1/2. This makes the average age to ejaculating semen around the age of 13. But this is only an average. Puberty in boys is considered normal if it starts as early as 9 or as late as 16. Hence, some boys, even though they are normal, will not gain the ability to ejaculate until they are nearly 18 years of age or they may start as soon as 10.

Usually when a boy begins to develop too early, it is an indication of problem. Even when no problem is found, the boys tend to be smaller than average in height and have weaker bones. After searching through some records, I found the youngest age of a boy being able to ejaculate was eight.2 There are some who claimed they started as young as six, but there is no supporting evidence. The youngest age verified of a boy fathering a child is 11.1 The cases of these very young ages are extremely rare.

"Britain’s youngest father identified publicly is Sean Stewart. In 1998 he became a father aged 12 when the girl next door, 15-year-old Emma Webster, 15, gave birth in Sharnbrook, Bedford. They split up six months later." [Times Online.]
Sexual Behavior in the Human Male, Alfred Kinsey

You have two good answers from @Kate and @Todd.

There are no known problems masturbating at 8.

Ejaculation needs you to be in puberty
and about 9 months after pubic hair (google it) appears at base of penis.

There are recorded cases of boys ejaculating at 10
and a number of Questions on here from boys claiming 10 - 11 - 12
but more usual age is 12 - 13 -14.

There is little modern evidence that boys starting early have weak bones
or miss growth spurts or are any shorter than genetic parents.

Boys can usually have orgasms much earlier than puberty
but just don't get semen.

+

You can of course google any word you don't understand.

Well I had my first at 15, i was kinda a late starter though, it depends on where you are developmentally, usually it happens after your testicles start growing and you start getting pubes

Own experience

umm well to be perfectly honest id say about 12 or 13 at least thats when i started to but if your 10 you have bigger stuff to worry about than masterbation. like your school work and helping your parents :) hope that helped

13-14 & you should be more into baseball,fishing or games.You will grow up in time,Enjoy just being a kid.

12

there i no age, my brother.