Our wonderful Associate Recipe Consultant Gail came up with this, I'm sure it will be very helpful to many!
Weight versus Volume
Somewhere along the road of life, most of us have learned that 1 pound equals 16 oz and 8 oz equals cup. What many of us have NOT learned is that they are two different units of weight which should not be used interchangeably. BEWARE! You may be sabotaging your own progress by doing so.
Different foods have different densities. What this means to you is that ½ cup (4 oz in volume) of one food may not always weigh out to 4 oz on the scale. Just to make a point here's an extreme example: try stuffing an 8 oz measuring cup as full as humanly possible with uncooked spinach leaves and put it on the scale-- nowhere near 8 oz weight is it? So, if you use units of weights and volumes interchangeably with this program, you may be eating either too much or not enough of a given food.
For best results, weigh proteins on a scale, measure other foods in a measuring cup. If you're cooking fruits, measure them before cooking since they collapse and their natural sugars condense with cooking. If you're cooking grains, measure after cooking.
If you really insist upon weighing all foods, we suggest you do this first: measure your food by volume first, in a measuring cup, then pop it on the scale and note the weight. Keep a chart of your findings you can refer to as a reference tool. That way, if you know the weight of ½ cup of potato, for example, the next time you can weigh it on your scale.
...or continuing the recommended method of weighing proteins, measuring everything else in measuring cups is good, too. 
Egg Whites
We don't weigh egg whites, nor do we worry about grams of protein. Each egg white (taken from large egg) is considered to be the equivalent of 1 oz protein.
If you're using pasteurized egg whites (which you really only need if you're using them raw, as in smoothies) our usual conversion is 2 tablespoons per egg white.
If you're using powdered egg whites, our usual conversion is 2 teaspoons per egg white.
Handy-Dandy Measurement Conversions
1 lb = 16 oz
1 cup = 8 oz (liquid or dry measure; NOT the same as 8 oz weight. Please read Weight versus Volume.)
1 cup = 16 tablespoons
1 cup = 48 teaspoons
1 oz (liquid or dry measure only) = 2 tablespoons
1 tablespoon = 3 teaspoons
a dash = about 1/16 - 1/8 teaspoon
a pinch = about 1/8 teaspoon
a dollop = a rounded blob
scant = not quite that measure, for example a scant tablespoon is a little bit less than a full tablespoon