Extract Potential of Sweet Potatoes

Does anyone know (roughly) the extract potential of fresh sweet potatoes? I'm working on brewing my pumpkin ale today and I'd like to be able to account for the sugars gleaned from the sweet potatoes in figuring efficiency.

Sweet potatoes are mostly water, but you can figure 25% carbs by weight.

So I dug up some nutritional information this evening and it looks like sweet potatoes are 17.7% carbohydrates so their extract potential is:

(0.177)(46 ppg) = 8 ppg

This seems reasonable to me. When I neglected the contribution of the sweet potatoes I was getting a brewhouse efficiency of 94% which is the extreme high end of what my process is capable of. With the sweet potatoes included at 8 ppg, my brewhouse efficiency came down to 88% which is more believable. I'm pretty consistent at 88%-90% brewhouse.

+1 to the above. Thanks for the tip, I just used it to calculate the efficiency for my batch that I did not too long ago. 8 ppg worked perfectly for me.