First decide what information is missing
A food without a label may be a single ingredient, a homemade dish or a meal somebody else prepared. Those situations need different references. An unlabelled apple can be matched to an appropriate food record. An unlabelled casserole needs recipe information, or an estimate with much greater uncertainty.
USDA FoodData Central provides food composition records. Search for the food and inspect the description before using its nutrition values. Match the preparation and food form as closely as possible. Raw, cooked, drained, sweetened and unsweetened entries are not interchangeable simply because the food name is similar.
Use a known amount with a matching record
If a record gives calories per 100 grams, multiply that value by the grams you ate and divide by 100. For example, a hypothetical food listed at 80 calories per 100 grams would contribute 120 calories for 150 grams. These numbers illustrate the formula; they are not a reference value for a particular food.
A kitchen scale can help establish the portion amount. Subtract the plate or bowl weight. If the record describes only an edible portion, match the amount to that description rather than including packaging or discarded parts.
When you cannot weigh food, use the record's specified serving measure if it matches what you have. A loosely described “bowl” or “large spoon” is an estimate, not a standard portion.
Measure homemade food from its ingredients
For a recipe you made, record ingredient quantities and add their estimated calories. Include cooking fats, sauces and toppings. Divide the batch into equal portions, or use the finished batch weight for a reasonably well-mixed dish.
Do not apply a raw ingredient's calorie density to the finished weight of a cooked recipe. Water absorbed or lost during cooking changes weight. Our homemade food guide gives a worked example for the full batch and a weighed serving.
Use a label when one is available
An ingredient may have arrived in a package even though the meal has no label. Keep that package's nutrition information for the amounts you use. Check whether its values are per serving or per 100 grams, and whether the serving amount matches yours.
The FDA label guide explains serving-based nutrition information. A barcode lookup can help find a product, but check its returned details against the actual package. Our barcode guide explains why identifying a product and recording its amount are separate steps.
When you do not know the recipe or weight
Ask for ingredients or published nutrition information if it is available. Otherwise, use a comparable food record or a photo estimate and note the unknown quantities. Hidden oil, sauces and fillings can change the result. Avoid treating a very precise-looking number as a measured one.
Heyberry can estimate a meal from a photo or description and lets you review foods and amounts. Meal logging requires Pro, and there is no published independent accuracy benchmark. See the photo calorie counter for its workflow. For a paper record of what you know, use the free food diary template.