Those semi trucks are much longer than 18 feet. I have a old Mark III Lincoln that longer than 18 feet. If I was going to by the choices given, I would say he would be around the 12 meters / 39 feet size. But the other choices are getting more like the size of the combiners. Oh yeah and M.E.G.A.S. is 80 feet tall :thumb

The Other Choises are from the MP Convoy booklet too

I go for about 9 meters tall, 6 is just a bit to small.

Those semi trucks are much longer than 18 feet. I have a old Mark III Lincoln that longer than 18 feet. If I was going to by the choices given, I would say he would be around the 12 meters / 39 feet size. But the other choices are getting more like the size of the combiners. Oh yeah and M.E.G.A.S. is 80 feet tall :thumb

The Other Choises are from the MP Convoy booklet too

They are still too tall nonetheless. No matter where they came from. :thumb

I would say between 30 and 40 feet.

G1 Prime was massive. Here is a pic to get an idea of his scale to humans.

 

 

The pic in my sig gives you his scale to Beast Wars TFs.

I figured Prime to be a little smaller than a Gundam.

As for the pic with Wheeljack, Prime, Spike, and BB don't forget that perspective can distort size

I know the humans are usally up to Prime's knee.

since a Tractor Trailer is roughly 12-14 feet high and Prime/Convoy is roughly 2 1/2 times as tall as he is high in truck form i'd say he's about 30-35 feet high or roughly 9-11 meters tall.