Measuring serving sizes without a scale?

I am looking up calories for certain items and when they come up in "ounces" I am not sure how to measure a proper serving size.  I don't have a food scale and have been assuming that 5.5 ounces could be measured as a little more than half a cup, but I have no idea if that is actually true.  Does anyone know a reliable way to measure serving sizes based on weight without a food scale?  The food I am looking up right now is Chinese food such as broccoli beef.

Thanks so much for the help!

You should use cup measures and convert to ounces. For instance, if you put the broccoli beef in a liquid measuring cup and it comes up to the 2/3 line...divide 8 by 3 and multiply by 2 this will give you 5.3 ounces ROUGHLY. Remember that what your really trying to do is have a good estimate of calorie intake and it doesn't have to be exact. (Being exact will not make you much more efficient in your efforts) I usually overestimate a little to be safe..like with serving sizes I'll be exact while eating but will enter a little more on my food log because preparation  and serving sizes may really vary. Good luck!!

Thank you!  I actually found a website that attempts to convert mass to weight: onlineconversion.com.  You enter a food item so it can estimate density and then you can convert across weight and mass (like you said it's all kind of an estimate).  1 fluid oz with most things is pretty darn close to 1 oz of weight.  Yay broccoli beef!

Thanks again!