AI have been looking online and cannot find the answer, I need to make a 16" heart cake next month but don't have that size pan.i came across a way to make a heart shaped cake using a square cake and a round cake of the same size, would I need to use a 16" square cake and a 16" round cake to make a 16" heart?

ACut out the 16" cake in cardboard and take the largest square pans you have and place the two round cake pans where the heart loops. Cut the second square to make the heart fit the shape you made...then you will know how many cakes you need, probably two eight or ten inch and two half sheet pans or squares...use what you have. How often will you use that size and shape pan...very expensive. Once you have figured out how to master this, you will be able to make any shape!!

AFrom what I saw, all I need to do is bake a square single layer cake and turn it so its a diamond shape, then bake a single layer round cake of the same size, cut it in half and then place each half on the top of the square to form a heart. I'm just not sure if I would need to do this with 16" pans or not, I can't seem to find the dimensions of a 16" heart pan.

You would not need a 16" sq pan.  As the other poster said, cut paper to see what size you need.  I think it will only need to be a 12"er. - both the round and sq should be the same size. 

You turn the sq on a board so it is diamond shape; cut the round in 1/2 and place one 1/2 on either side of one point of the sq - viola! you have a heart.

AThat makes sense!thank you both so much :)

AThe dimensions are going to come from the top of the cake,where the cake rounds would go. That should measure 16" across. From the top of the heart to the tip would be about 14-16 inches down from the top of the shape. One of each may not give you the height you need, that is why I said two of each shape and to make a cardboard shape of the shape you want. You can also go to global sugar arts and see if they have that size or Google it to get the dimensions. Hope this helps. VALERIE