Weigh the container before and after
Place the oil bottle or sauce jar on a scale, note the weight, use the ingredient, then weigh it again. The difference is the amount dispensed. This avoids trying to balance a hot pan on a kitchen scale.
Use a scale with a suitable resolution and keep the cap or lid in the same place for both readings.
Measure what entered the recipe, then document what left
For a dressing mixed into a salad, most of the dispensed amount may remain in the food or bowl. For frying, oil can remain in the pan, move into food, or leave with discarded crumbs. Home measurement cannot perfectly separate these paths.
If a measurable pool remains, you can weigh the cooled pan before and after cleaning or transfer the remainder to a tared container. State the assumption rather than pretending absorption is exact.
Marinades need a defined rule
If you calculate all marinade ingredients but discard much of the liquid, counting the entire batch can overestimate what was eaten. Weighing marinade before contact and the discarded remainder can give a rough retained amount, but juices from the food mix into the discard. For routine tracking, use one documented convention consistently and recognize its uncertainty.
Never reuse raw-meat marinade as a sauce unless it has been handled and cooked according to food-safety guidance.
Use the batch method for sauces
For a homemade sauce, calculate the whole recipe, weigh the finished sauce, then assign nutrients by the gram. If the sauce reduces, its water loss changes grams per spoon but not the batch’s energy total. Reweighing the final yield captures that concentration.
What precision is worth pursuing
Measuring a tablespoon by volume can be perfectly adequate for everyday cooking. Before-and-after bottle weights help when pours vary or tracking consistency matters. Choose the least burdensome method that answers your question; food should not become a laboratory exercise.