How to Use a Food Scale for Calorie Counting

Key takeaways

• To use a food scale for calorie counting, set your plate or bowl on the scale, press tare so it reads zero, add the food and log the grams.
• Then match the grams to a per 100 gram figure from the package or USDA FoodData Central. USDA lists olive oil at 884 calories per 100 grams, so every gram of oil you pour is 8.84 calories.⁴
• Eye estimates miss by a lot. In Gibson's 2016 study, people judged pre-weighed foods in cups and spoons by sight, and only 7 of 24 foods and drinks came within 25 percent of the true weight.¹
• Weigh a meal you eat often one time, save it, and reuse it. After that the scale only comes out for new foods.
• A scale is optional. Package labels, measuring spoons and a plain description of the portion all work, and you can stop weighing whenever it stops helping.

How to use a food scale for weight loss

A food scale gives you one number, the weight of what's on your plate. The calories come from matching that weight to a food's nutrition data. Here's the routine.

• Set the scale on a flat counter and switch it to grams.
• Put your empty plate, bowl or pan on it and press tare. The display goes back to zero, so the dish isn't counted.
• Add one food and write down the grams. Press tare again before you add the next food, and each item gets its own number.
• Look up that food's calories per 100 grams on the label or in a food database. Multiply by your grams and divide by 100.
• Log it right away, before you sit down to eat.

How to weigh food for calorie counting

Use grams rather than ounces. A gram is a much smaller step, so small amounts of dense food still register, and per 100 gram figures turn the math into moving a decimal point.

Weigh food in the same form as the entry you log it against. Oats show why. USDA lists regular dry oats at 379 calories per 100 grams and oatmeal cooked with water at 71, because cooking adds water and water adds weight but no calories. Weigh the oats dry and use the dry entry, or weigh the cooked bowl and use the cooked entry, but never mix the two.⁶⁷

The same goes for meat, rice and pasta. Raw and cooked weights differ, so check which one your database entry describes.

For anything sticky or poured, weigh the container instead of the food. Note the jar or bottle weight, serve yourself, weigh it again, and the difference is what you took. Nothing has to come off a spoon.

Which foods to weigh first

Start with foods that pack many calories into a small amount, because a small miss on those moves the total the most. Oil is the clearest case. USDA weighs a tablespoon of olive oil at 13.5 grams, with 884 calories per 100 grams of oil.⁴

Nut butter is next. USDA lists smooth peanut butter without salt at 598 calories per 100 grams and weighs its 2 tablespoon serving at 32 grams. A spoonful scooped from the jar can sit well above or below a level tablespoon.⁵

Then weigh grains and cheese, which tend to get served by the scoop, the handful or the slice.

Rice is a good example. In Gibson's study, both portions of rice were judged by eye at well above their true weight.¹

Fruit and vegetables can wait. Weigh them later if you like, or skip them.

How accurate are portion guesses by eye?

Not very, according to the studies that tested it. In Gibson's 2016 study, people practiced with measuring cups and spoons, then estimated 42 pre-weighed portions without them. For 24 regularly shaped foods and drinks, only 7 estimates came within 25 percent of the true weight and 2 within 10 percent. Chicken breast, fish fillets and steak were each judged more than 50 percent heavier than they really were.¹

Practice helps a little. In Byrd-Bredbenner's 2004 study, 113 young adults estimated portions of 36 foods. After a short time using a tennis ball and a golf ball as size guides, their accuracy improved and stayed better once the guides were gone. Even with the guides, they were accurate only about 60 percent of the time.²

Food reports add their own gap. In Lichtman's 1992 study, 10 people who believed their diets weren't working had their actual intake measured for 14 days. Their own food reports came in 47 percent below what they actually ate, on average, while their metabolism was within 5 percent of predicted.³

None of this means people are careless. Portions are hard to judge, and a scale takes the judging out of it for the foods where a miss matters most.

Weigh a repeat meal once, then save it

Most people eat the same few breakfasts, lunches and snacks over and over. Each of those only needs weighing one time.

• Pick the meal you eat most often and weigh every part of it the next time you make it.
• Save it in your log as a named meal with those weights.
• Log it from the saved version from then on. Reweigh only when you change the recipe, the amount, the bowl or the brand.
• Weighing your usual pour or scoop also trains your eye. Once you've seen what 27 grams of peanut butter looks like on your own knife, you'll recognize it at a friend's table.

Do you need a food scale to count calories?

No. A scale makes the number more exact, but a log without weights still works, and plenty of people never weigh anything. These options cover most meals.

• Use the package. A single-serve yogurt, a granola bar or a can of soup already has its weight and calories on the label, so log the whole thing or the fraction you ate.
• Use measuring cups and spoons, leveled off, for rice, cereal, oil and nut butter. They're less exact than grams, but a leveled cup is a measurement rather than a guess.
• Hand sizes are rougher than they look. In Gibson's study, a thumb tip averaged 4.8 milliliters, just under a teaspoon, even though public advice often treats it as a tablespoon.¹
• Describe the portion in plain words, such as half a cup of rice or a thin layer of butter on one slice of toast. A specific description beats a bare food name.
• At restaurants, check whether the menu lists calories, and log the size you were served.

When weighing food feels like too much

A scale is a measuring tool, not a rule you have to follow. If weighing food makes meals stressful, makes you anxious when you can't weigh, or pushes you toward eating less than you need, put the scale away. If food or numbers start to take over your thoughts, talk with a doctor, a therapist or a registered dietitian.

A note on medical advice

This article is for general information and isn't medical advice. Talk with your clinician about your own situation.

Worked example

Say you spread peanut butter on toast and figure it's about a tablespoon. Put the jar on the scale before you start and it reads 412 grams. Afterward it reads 385 grams, so 27 grams went on the toast. USDA lists smooth peanut butter without salt at 598 calories per 100 grams, or 5.98 per gram, and 27 times 5.98 is about 161 calories. USDA's 2 tablespoon serving weighs 32 grams, so a guessed tablespoon is 16 grams, about 96 calories. Your usual spread is closer to 27 grams. Save the toast as a meal at that weight, and tomorrow there's nothing to weigh.⁵

A closer look

In Gibson's 2016 study, 67 people looked at 42 pre-weighed foods and drinks and estimated each one in cups and spoons, with no measuring tools at the table. A small serving of rice that weighed 55.2 grams got a median estimate of 83.8 grams. A 5.4 gram dab of honey was judged at 21.5 grams, about four times its weight. When an estimate was clearly wrong, it was usually too high.¹

Questions and answers

Related guides

• How to track calories
• How to read a nutrition label
• How to count macros
• Calories in olive oil, spoon by spoon
• Dry oats and cooked oatmeal, calories by the cup
• Calories in peanut butter
• Describing portions for an AI estimate

Sources

1. Journal of Nutritional Science. Gibson. 2016.
2. Journal of Human Nutrition and Dietetics. Byrd-Bredbenner. 2004.
3. New England Journal of Medicine. Lichtman. 1992.
4. USDA FoodData Central, Oil, olive, salad or cooking. U.S. Department of Agriculture. 2019.
5. USDA FoodData Central, Peanut butter, smooth style, without salt. U.S. Department of Agriculture. 2019.
6. USDA FoodData Central, Cereals, oats, regular and quick, not fortified, dry. U.S. Department of Agriculture. 2019.
7. USDA FoodData Central, Cereals, oats, regular and quick, unenriched, cooked with water, without salt. U.S. Department of Agriculture. 2019.