When you create a recipe in MacroFactor, the app will auto-sum the weights of the ingredients if all ingredients contain information about either:
Nutrition data associated with mass units (grams, ounces, etc.)
Nutrition data associated with volume units (milliliters, fluid ounces, etc.) and
The density of the ingredient
If at least one ingredient only reports nutrition data associated with volume units without reporting density, there’s not a way to confidently interconvert between mass and volume units. Most foods and beverages have densities ranging from 0.5-2g/ml, which represents a pretty large range of plausible masses if only volume units are known. In other words, if you added 100ml of an ingredient to a recipe, you may have added 50g of that ingredient, or 200g of that ingredient. If MacroFactor doesn’t have the necessary information to confidently and accurately interconvert between mass and volume units, it’s not going to simply make a guess, which could result in significant error.
If you’d like MacroFactor to auto-sum the ingredient weights for a recipe, make sure you’re only adding ingredients that provide mass units when logging. Most of the time, this will mean substituting branded foods for common food equivalents. For example, here’s how a blueberry muffin recipe might look if I added a particular brand of milk that only reports volume units:
And here’s how the same recipe would look if I used the equivalent milk entry from the “common foods” list:
Many manufacturers of branded food items only report volume units for liquids, sauces, and pastes, which doesn’t allow for the interconversion between volume and mass units. MacroFactor’s “common foods,” on the other hand, come from high-quality research databases that almost always contain the necessary information for converting between volume and mass units.
However, most of the time, we’d recommend not using the auto-summed weight anyways. The auto-sum feature is primarily intended to save time when creating recipes that don’t require cooking, because cooking foods generally results in some fluid loss. Using the blueberry muffin example above, I generally find that my muffins lose about 15% of their total mass during baking, because some water will be lost in the form of steam when the batter goes into a hot oven:
Depending on the cooking method, temperature, time, and foods included in the recipe, cooking may cause fluid losses ranging from 5-50%. So, using the auto-summed weight would result in underestimates of both the energy and nutrient density in the final (cooked) dish.
So, most of the time, we’d recommend re-weighing the finished recipe after cooking, and entering the cooked weight of the recipe in the “total weight” cell, replacing the auto-summed weight.
On the other hand, you probably don’t need to re-weigh the finished recipe in instances where there’s no cooking required. So, if you’re making a recipe for a salad, a no-bake dessert, a sauce or dressing that doesn’t require any cooking (for example, an aioli or a vinaigrette), or any other recipe that doesn’t require cooking, you’re probably fine to use the auto-summed weight, if it’s available.