Carbs, protein, fat and alcohol - how many calories per gram?
The four numbers that explain almost everything about how food becomes energy.
Why these numbers matter
Before you can make sense of a nutrition label, a macro tracker, or even a basic calorie count, you need to know one thing: not all macronutrients contain the same amount of energy per gram. This is foundational nutrition knowledge and once you know it, a lot of other things start to click into place.
There are four things in food that contain calories. Just four. Everything else - water, vitamins, minerals, fibre - contributes zero calories. So when you're looking at any food and asking "where are the calories coming from?" the answer is always some combination of these:
Carbohydrates: 4 kcal per gram
Carbohydrates are the body's preferred source of energy. They're broken down into glucose, which your body uses immediately for fuel or stores as glycogen in your muscles and liver for later.
At 4 kcal per gram they're a relatively efficient energy source - not as energy-dense as fat, but faster to access. This is why carbs are the go-to fuel for high intensity exercise and why cutting them dramatically can leave you feeling flat and fatigued, at least initially.
Common high-carb foods: bread, rice, pasta, fruit, oats, legumes, most packaged snack foods.
Protein: 4 kcal per gram
Protein contains the same number of calories per gram as carbohydrates, but it behaves very differently in the body. Rather than being a primary fuel source, protein's main job is building and repairing tissue - muscle, skin, enzymes, hormones.
What makes protein particularly interesting from a calorie perspective is its thermic effect. Your body burns roughly 20-30% of protein calories just in the process of digesting it. So while 100 calories of protein and 100 calories of carbs look the same on a label, your body nets fewer calories from the protein after digestion.
Protein is also the most satiating macronutrient - it keeps you full longer than carbs or fat, which matters a lot if you're trying to manage your overall intake.
Common high-protein foods: meat, fish, eggs, dairy, legumes, tofu, protein supplements.
Fat: 9 kcal per gram
Fat contains more than double the calories per gram of carbs or protein, which is why high-fat foods are so energy-dense. A tablespoon of olive oil (around 14g) contains about 100 calories - mostly from fat.
This doesn't make fat bad. Fat is essential for hormone production, absorbing fat-soluble vitamins (A, D, E and K), brain function, and keeping you satisfied after a meal. The energy density just means portion sizes matter more with high-fat foods than with most others.
It's also worth noting that not all fats are equal nutritionally - unsaturated fats from foods like avocado, nuts and olive oil behave very differently in the body to saturated fats from processed foods - but from a pure calorie perspective, fat is fat at 9 kcal per gram regardless of the source.
Common high-fat foods: oils, butter, nuts, seeds, avocado, cheese, fatty meats, full-fat dairy.
Alcohol: 7 kcal per gram
This is the one that surprises most people. Alcohol sits between carbs and fat at 7 kcal per gram - and unlike the other three, it provides no nutritional value. No building blocks, no essential functions, just energy.
What makes alcohol particularly relevant for anyone tracking calories is that it's easy to underestimate. A standard glass of wine contains roughly 120-130 kcal, a pint of beer around 180-200 kcal, and a cocktail can easily hit 300+ kcal depending on what's in it. These calories add up quickly and they're not always front of mind when people are tracking their food.
Alcohol also affects the way your body processes other macros - when alcohol is present, your body prioritises metabolising it first, which means fat burning is essentially paused until the alcohol is cleared. Worth knowing.
How to use this information
These four numbers are the foundation of reading any nutrition label with confidence. When you look at the macronutrient breakdown on a packet and want to estimate the calories yourself, just multiply:
Grams of carbs × 4
Grams of protein × 4
Grams of fat × 9
Grams of alcohol × 7
Add them together and you'll get a number close to the energy listed on the label. It won't be exact - labelling allows for some variance and the Australian system uses modified energy conversion factors - but it'll be close enough to be useful.
And if you want all of this on one handy reference page, grab the free Nutrition Cheat Sheet - it's exactly this information plus kJ conversions and a glossary of key terms, all on one page.
Want to see how these macros play out across thousands of Australian foods? The Australian Calorie & Nutrition Guide has FSANZ-sourced data organised the way you actually shop.
