When a patttern asks for Double Knitting Weight Yarn… 
is this a sport weight yarn…This is for a baby blanket.
I have yarn but not sure which one I can use.
thank you
Substitution
Most of the time the two are interchangeable. There is a very slight difference, but then again nearly all “sizes” are slightly different from manufacturer to manufacturer. For a baby blanket, as long as your tension is even throughout, it shouldn’t really matter. If you are afraid that the difference in size will be dramatic, do up a small swatch to see how much of a difference it will be.