Short answer
It depends on the food, by roughly 26 times. One hundred grams is a fixed weight, not a fixed amount of energy. Water and fibre weigh a lot and carry little energy; fat weighs little and carries a lot.
That is why "how many calories is 100 grams" has no useful answer on its own. The weight tells you how much you have. Only the food tells you what that weight is worth. A kitchen scale reading of 100g is the start of the question, not the end of it. If your question is the other way around, use the 100 calories to grams calculator.
100 grams of thirteen common foods
Values are rounded from USDA FoodData Central entries for the plain, unseasoned versions. Your packet may differ, and a labelled product should always beat a general reference.
| Food | Calories | Protein | Roughly what 100g is |
|---|---|---|---|
| Broccoli, raw | 34 Cal | 3.0g | A large double handful of florets, enough to fill a cereal bowl. |
| Greek yogurt, plain nonfat | 61 Cal | 10.0g | A little under half a standard single-serve tub. |
| Potato, raw with skin | 77 Cal | 2.0g | One small potato. |
| Banana | 89 Cal | 1.1g | One medium banana, peeled. A large one can reach 130g. |
| White rice, cooked | 130 Cal | 2.7g | A little over half a cup, cooked. Roughly 33g of it dry. |
| Egg, whole raw | 143 Cal | 12.6g | Two medium eggs out of the shell. |
| Pasta, cooked | 158 Cal | 5.8g | About three quarters of a cup, cooked. Roughly 40g dry. |
| Avocado | 160 Cal | 2.0g | Two thirds of a medium avocado, flesh only. |
| Chicken breast, cooked skinless | 165 Cal | 31.0g | One modest fillet, a bit larger than a deck of cards. |
| Cheddar cheese | 402 Cal | 25.0g | About four sandwich slices. |
| Almonds | 579 Cal | 21.2g | About two thirds of a cup, roughly 80 nuts. |
| Peanut butter | 588 Cal | 25.1g | About six tablespoons, a third of a small jar. |
| Olive oil | 884 Cal | 0.0g | Seven tablespoons. It fits in a small glass. |
Two things stand out. The first is the spread: the bottom of this table and the top differ by about 26 times for the same weight. The second is that protein and calories do not move together. Greek yogurt at 61 Calories carries 10g of protein, while avocado at 160 Calories carries 2g. If protein is what you are tracking, weight alone will mislead you.
To convert any of these to the amount you actually ate, the nutrition per 100g calculator scales calories and macros together, and the per-100g calculation guide explains the multiplier behind it.
What 100 grams looks like
The descriptions in the table are approximations meant for a first guess, not replacements for weighing. They are worth knowing anyway, because most people log at least some meals away from a kitchen.
The useful pattern is that dense, dry, and oily foods look small at 100g, while watery foods look large. One hundred grams of olive oil is about seven tablespoons and disappears into a pan. One hundred grams of broccoli fills a bowl. If a food surprises you by how little of it 100g is, that is usually a sign it is calorie dense.
Cooking oil is the one worth internalising, because it is poured rather than portioned and rarely gets logged. The cooking oil calorie calculator handles spray, poured, and left-in-the-pan amounts separately.
100g raw is not 100g cooked
This trips up more logs than the conversion arithmetic does. Meat loses water as it cooks and gets lighter, so 100g of cooked chicken came from noticeably more than 100g raw. Rice and pasta go the other way, absorbing water and getting heavier: the roughly 33g of dry rice behind 100g cooked is why dry and cooked figures look so different.
Neither figure is wrong. They describe different states of the same food, and the mistake is mixing them, such as weighing rice cooked and then logging a dry-weight database entry. Pick one state, and keep the log consistent about which. The raw to cooked weight calculator converts between them, and the raw vs cooked guide covers which state to standardise on.
Why labels use 100 grams
One hundred grams is a comparison standard, not a serving suggestion. UK and EU nutrition declarations are required per 100g or per 100ml, which lets you compare two products directly without doing arithmetic on mismatched serving sizes. Australian and New Zealand panels carry a per-100g column beside a per-serve column for the same reason.
US Nutrition Facts panels lead with a serving instead, which is why an imported product and a domestic one can look incomparable at a glance. If a label gives you kilojoules rather than Calories, the kJ to Calories chart converts the energy figure before you scale it.
Getting better at estimating
The reliable way to improve is to weigh a food a few times, then stop. Weigh the rice you normally cook, the oil you normally pour, and the cheese you normally grate, and note what those amounts looked like. After a handful of repetitions the estimate for that specific food gets much closer, and you do not need the scale for it any more.
Accuracy also matters unevenly. Being 20g out on broccoli costs about 7 Calories. Being 20g out on peanut butter costs about 118. Spend the attention on the dense foods and let the vegetables be approximate.
For the meals you eat repeatedly, weighing once and saving the result does most of the work. The weighed repeat meal calculator is built for that, and tracking macros without a food scale covers labels, household measures, and hand references for the times a scale is not an option.
What these numbers cannot do
They are general reference values for plain foods. Brand, cut, fat content, ripeness, added oil, and preparation all move them, sometimes a lot. A printed label on the product in front of you is better evidence than any table, including this one.
This is general information for adults, not dietary advice, and none of it sets an appropriate intake for you. Speak with a qualified clinician or registered dietitian for personal guidance, and pause tracking if it starts causing guilt, compulsive checking, or fear around food.
Calorie and protein figures are rounded from USDA FoodData Central entries for plain, unseasoned foods. Label-format rules come from NHS guidance on reading food labels, FSANZ nutrition information panels, and the FDA Nutrition Facts label.