You can specify the height of the box in em’s. EM is a unit that is equal to font’s height. So if you want your form to be 10 lines height, just speicfy height: 10em;

I also felt it’s a bit weird to type on the last line. It makes you feel that you are almost out of room. So I added one line padding at the bottom. You can’t type on that line, but it just adds that feeling of security padding-bottom: 1em;