If your pill is scored...has a line down the middle, then it's the same dosage on each side of the pill. That is, half of the dosage on each side. I am not sure what Ultram looks like. But I do know about scored pills.
Ive been on Tramadol for over a decade, and I break them in half all the time. They arent scored, so I doubt if you get exactly 1/2 a dose, But its close enough for government work, as they say lol. I wouldnt recommend doing this with just any pill though, and for sure be very careful with extended release stuff, that should never be broken or crushed.