Measuring and Estimating Portion Size

The real challenge to recording food intake is figuring out how much food or drink was actually consumed.

As many of you know, without an accurate portion size, the analysis of your dietary intake will be skewed. An inaccurate calorie intake assessment will make it harder for you to interpret results or modify your intake to meet desired goals.

The best way to assess portion size is to measure it. The more you measure, the better you will be at visually assessing portion size. This is especially important when you dine out. This does not necessarily mean that you always have to measure everything that goes into your mouth. You can measure foods and drinks a few times to learn what the volume or weight looks like on the dishes you typically use. To avoid "drift," you will want to periodically measure items again to confirm that your "eyeballing" of portion size is still accurate.


I find that I am more likely to measure if I have clean measuring cups and spoons available. Therefore, I own two inexpensive sets. I also own one inexpensive spring-loaded food scale. You can buy digital food scales, but be aware that there is a huge range in price. I find that the scales under $30 do just fine, and they can be found in stores such as Bed Bath & Beyond, Linens & Things, Target, or online.

Measuring food weight can come in handy when measuring with spoons or cups is not practical. For instance, if you eat homemade bread or buy unsliced bread, you may want to weigh your own slice of bread to see if you generally slice thick or thin. One standard slice of commercial bread weighs about 1 oz, so many bread items in the nutrient database will use 1 oz slices. If you do not account for something like thick bread, you might be underestimating your calorie, carbohydrate, and possibly sodium and dietary fiber intake.

High Ticket Items

Some foods are so high in calories that underestimating portion size will result in a significant underestimation of calorie intake. Therefore, I am particularly careful to measure the following items:

  • Fats and oils
  • Nuts and seeds
  • Avocado, guacamole, pesto, dips, and salad dressings
  • Dried fruit and fruit juices
  • Syrups and honey
  • Chocolate

These foods that I tend to overeat (that is, my idea of a serving is a very large portion that is high in calories) I am careful to measure. I recommend that you create your own list. For instance, tortilla and potato chips have gone stale in my home, while I have to count out crackers to avoid eating the entire box. Here is my list:

  • Low fat ice cream, frozen yogurt, or sorbet
  • Crackers
  • Pizza

I rarely eat the items below, but when I do, I am very careful to control portion size.

  • Cake, pie, cookies, doughnuts, pastries, croissants
  • Gourmet ice cream (e.g. Haagen Dazs, Ben & Jerry's)
  • Sweetened beverages of any type
  • Deep-fat fried food.
  • Very high-fat meats such as ribs, bacon, and pork sausage

What I don't measure as precisely

Non-starchy vegetables:

  • A standard serving size is 1/2 cup cooked, or 1 cup raw.
  • I serve myself large portions of these very low calorie density foods, but I am careful to measure the amount of added fat.
  • I try to eat 2-3 servings at dinner, with a goal to fill half of my plate with vegetables.
  • At lunch, I aim for at least 1 serving.
  • Examples of non-starchy vegetables include leafy greens (e.g. lettuce, spinach), sweet peppers, cabbage, squash, onions, tomatoes, carrots, garlic, green beans, broccoli, and cauliflower.
  • Vegetables that contain 5 grams of total carbohydrates or less per standard serving are considered non-starchy.

Whole fresh fruit:

  • A standard serving size is 1 medium piece of fruit (the size of a baseball), 1 small banana, 1/2 cup of fruit pieces, or 1 cup of berries or melon. I aim for roughly those serving sizes.
  • Most of us do not eat enough fresh fruit. I aim for 2-3 servings of fresh fruit daily.
  • Although I try to follow standard fresh fruit serving sizes, I will eat a larger piece of fruit if that is what is available. This is not the case with dried fruit or fruit juice. I am careful to measure portion size as the concentration of sugar is quite high.

Useful Measurement Equivalents

The measurements provided in the table below will help you enter quantities correctly in MyNetDiary when the expected unit of measure is not available. For instance, if you consumed 1 teaspoon of honey, but the only unit of measure available is 1 tablespoon, you can enter 0.33 tablespoon to get the correct quantity.

English Metric
1 teaspoon = 0.33 tablespoon 5 ml
3 teaspoons = 1 tablespoon 15 ml
2 tablespoons = 1 fl oz = 1/8 cup or 0.125 cup 30 ml
4 tablespoons = 2 fl oz = 1/4 cup or 0.25 cup 60 ml
6 tablespoons = 3 fl oz = 1/3 cup or 0.33 cup 90 ml
8 tablespoons = 4 fl oz = 1/2 cup or 0.5 cup 120 ml
16 tablespoons = 8 fl oz = 1 cup 240 ml
16 fl oz = 2 cups = 1 pint 480 ml
32 fl oz = 4 cups = 2 pints = 1 quart 960 ml (just less than 1 Liter or 1000 ml)
1 oz 28 grams
3.5 oz 100 grams

Estimating Portion Size

If you have already started recording your intake, then you know how difficult it is to estimate portion size when dining out. If you are dining out and the restaurant does not offer nutrition information, you can ask your server to check on approximate serving sizes. Sometimes they will, sometimes they won't. If the restaurant can tell you the weight of raw meat, fish, poultry or game, then assume shrinkage of about 25% during cooking. For example, a raw 4 oz beef patty will likely be closer to 3 oz when cooked.

Keep in mind that we tend to underestimate portion size when food is served on large plates or when drinks are served in short deep glasses.

If you do not have web access while dining out, I recommend printing the Serving Size Card from the National Heart Lung and Blood Institute. Simply fold the printout along the dotted lines and place it in your purse or wallet. Here is a summary of what's contained in the Serving Size Card. The visual cues are on the right side. For instance, 1/4 cup of raisins is equivalent to the size of 1 large egg.

Grain Products Vegetables, and Fruit
1 cup cereal flakes = 1 fist
1 pancake = 1 compact disc
1/2 cup cooked rice, pasta or potato = 1/2 baseball
1 oz slice of bread = 1 cassette tape
1 cup of salad greens = 1 baseball
1 baked potato = 1 fist
1 medium piece fruit = 1 baseball
1/2 cup fresh fruit = 1/2 baseball
1/4 cup raisins = 1 large egg
Dairy and Cheese Meat and Protein Alternatives
1 1/2 oz cheese = 4 stacked dice
1/2 cup ice cream = 1/2 baseball
3 oz meat, fish, or poultry = 1 deck of cards
3 oz grilled/baked fish fillet = 1 checkbook
2 tablespoons peanut butter = 1 ping pong ball
1 teaspoon margarine, butter, or spreads = 1 dice

For those of you who cannot visualize a baseball, 1 tennis ball is roughly equal to 1/2 cup. And for those of you who haven't seen a pair of dice in decades, the tip of a woman's thumb (from the first joint upwards) is about the size of 1 teaspoon.

If you enjoy quizzes, then click on the National Heart, Lung, and Blood's Portion Distortion link to see if you can guess the calorie content of some common foods and drinks.

If you enjoy reading, then I recommend the book, Mindless Eating by Brian Wansink. Wansink has conducted much research in the area of "why we eat more than we think," and he reports his findings with humor and empathy. I have learned a lot about how environmental cues affect our eating behavior by reading his book.


Good luck with your new adventure in recording diet and physical activity. I am a big supporter of monitoring one's behaviors as a way of effecting change and meeting desired goals. I do it myself! I look forward to sharing more information about nutrition with you in the future.

Katherine Isacks, MPS, RDN, CDE
Disclaimer: Please note that we cannot provide personalized advice and that the information provided does not constitute medical advice. If you are seeking medical advice, please visit a medical professional.

This article can be found at