According to WebMD, digestible or net carbohydrates are calculated by taking the total amount of carbohydrates and subtracting indigestible sugar alcohols and fiber. If a product label is available for the food, it is a simple and quick calculation.
- Find the total number of carbohydrates
Read the product label to determine the total number of carbohydrates in the food. An estimate can be made using an online resource as well.
- Subtract any sugar alcohols from the total carbohydrates
Subtract any sugar alcohols from the total carbohydrate number. Sugar alcohols are artificial sweeteners such as mannitol, sorbitol and xylitol.
- Subtract the total amount of fiber
Take the total amount of fiber listed on the label and subtract it from the previous result. Sources of fiber include fruits, vegetables and whole grains.