Fat Intake Calculator

This works out how much fat to eat in a day. It estimates your calorie needs from height, weight, age, gender and activity, then converts the accepted percentage ranges into grams, total fat at 20 to 35% of calories, and saturated fat under 10% and under 7%. The table repeats it for five weight goals, because a deficit changes the gram target as well as the calorie one.

The three macronutrients

Fat, along with carbohydrate and protein, is one of the three macronutrients supplying the energy your metabolism runs on. Dietary fat comes in several forms: saturated, trans, monounsaturated, polyunsaturated, and the omega-3 fatty acids. Fat is essential to normal body function, but eating more than you need leads to weight gain, and excess weight is linked to poor health outcomes. Our Body Fat Calculator covers the stored kind.

Fat is also the densest of the three. Protein and carbohydrate deliver about 4 calories per gram; fat delivers roughly 8.8 to 9. That is why a modest change in fat intake moves total calories more than the same change in anything else, and why fat targets are quoted as a percentage of calories rather than a flat number of grams.

The fats to limit

Saturated fat is among the more harmful types and comes mostly from animal sources: red meat, poultry and dairy. It also appears in some nuts, oils and seeds. Coconut and palm oil are especially high. There is genuine ongoing debate about how strongly saturated fat drives disease risk, but the mainstream position is unchanged. The Mayo Clinic, the American Heart Association and many others recommend a diet low in it, on the grounds that it raises "bad" low-density lipoprotein (LDL) cholesterol and increases the risk of cardiovascular disease and type 2 diabetes.

Trans fat occurs naturally in small amounts in some foods, but most of what people encounter comes from partial hydrogenation, an industrial process. Heavily processed food, fast food especially, tends to be high in it.

Trans fat is generally regarded as the worst dietary fat. It is not essential and has no known benefit to human health. It raises LDL cholesterol while lowering "good" high-density lipoprotein (HDL) cholesterol, which is a uniquely bad combination, and it increases the risk of coronary artery disease, obesity and type 2 diabetes.

One labelling trap is worth knowing. By law a serving containing less than 0.5 grams of trans fat can be labelled as having 0 grams. Eat several servings and those rounded-down halves add up. To avoid it properly, check that a product labelled 0 grams also has no ingredient containing the words "partially hydrogenated". Regulators have since moved against it directly, the US FDA revoked the safe status of partially hydrogenated oils in 2015 and required removal from the food supply, and the World Health Organization has pushed for a global elimination, so it is far less common than it was, but it has not vanished from every shelf.

The fats to keep

Monounsaturated and polyunsaturated fat are the two unsaturated types, found across many foods and oils, with polyunsaturated fat more common in plant sources. Studies show both, in reasonable amounts, help lower LDL cholesterol while potentially raising HDL. Olive oil, avocados and most nuts are the familiar monounsaturated sources; sunflower, soybean and walnut oils are polyunsaturated.

Omega-3 fatty acids are a polyunsaturated type concentrated in oily fish (salmon, mackerel, sardines) and have been found to lower the risk of coronary artery disease. They are also essential, meaning the body cannot make them and they have to come from food. Omega-6 fats are essential too and are abundant in most Western diets, so the practical gap is almost always omega-3.

The useful conclusion from the last two decades of research is that replacing saturated fat with unsaturated fat lowers cardiovascular risk, while replacing it with refined carbohydrate does not. What you swap it for matters as much as what you cut.

How much fat a day

There is no single rule. Some fat, particularly unsaturated fat, is beneficial. Children especially need fat, which is why whole milk rather than low-fat is generally recommended once breastfeeding stops. But any fat, including the healthier kinds, causes problems in excess. The working guidelines are:

• Keep saturated fat under 10% of daily calories. Holding it under 7% has been shown to reduce heart disease risk further, which is the stricter column in the table.
• Replace saturated fat with unsaturated fat wherever you can.
• Minimise trans fat.
• Keep dietary cholesterol under 300 mg a day.

Total fat sits at 20 to 35% of calories for adults, and that range shifts with age:

Young children need proportionally more because fat supports rapid brain development, which is why the toddler band starts where the adult band ends. This calculator uses the adult range.

Reading the table

On the defaults, maintaining weight takes 2,361 calories, giving a fat allowance of 54 to 94 grams with saturated fat under 27 grams, or under 19 grams on the stricter target. Cutting to lose 1 lb a week drops the calorie allowance by 500 and the fat range with it, to 42 to 74 grams.

That last point catches people out. Fat targets are percentages, so they shrink as calories do. Someone who cuts calories but keeps eating the same amount of fat has quietly raised fat from 30% of their intake to closer to 40%. The second chart shows the saturated ceilings falling across the same five goals for the same reason.

A note on the arithmetic: grams here are converted at 8.8 calories per gram of fat rather than the round 9 you usually see. That is the Atwater specific factor, and it is what the reference tables use. The difference is about two grams on a typical day, small, but it is why these figures may not match a calculation you do yourself at 9.

Making the numbers practical

Grams of fat are hard to picture, so a few anchors help. A tablespoon of any oil is about 14 grams of fat, essentially all of it. A tablespoon of butter is around 12 grams, of which roughly 7 are saturated, a quarter of a whole day's saturated allowance on the defaults. A medium avocado carries about 21 grams, almost all unsaturated. A hundred grams of salmon has around 13.

Read the labels for saturated fat first rather than total fat. Total fat tells you little on its own, since a handful of walnuts and a slice of processed meat can carry the same amount with completely different effects. The saturated line, and the ingredients list, are where the useful information is.

One more caution against cutting too hard: fat carries the fat-soluble vitamins A, D, E and K, and you need some in a meal to absorb them. Very low-fat diets can leave those short even when the food itself contains them. The goal is the right fats in the right amount, not the least fat possible.

Our Macro Calculator splits all three macronutrients at once, and the Calorie Calculator covers the calorie side in more detail.