If we look at the area of northern Orion when it's rising or by tilt-ing your head sideways when it's near the meridian, we can see the cross pattern made by Betelgeuse, λ Orionis, Bellatrix, and ω Orionis.  This pattern is similar in size and shape to the Southern Cross (Crux), but with some notable differences.  Overall, I would say it offers you a decent idea as to how big Crux looks.