Fat Intake Calculator

How to use the fat intake calculator

Start by choosing US or metric units. This switch changes the height boxes (feet and inches, or centimetres and metres) and the units of the answer (ounces or grams). The weight box has its own kg / lb selector, so make sure it matches the number you typed.

Then enter your age, sex, height and weight, and pick the activity level that fits a typical week. Finally set the Fats percentage: the share of your daily calories you want to take from fat. It starts at 25% and cannot go below 10%. Weight is the only other required field; a blank age or height is counted as zero, which lowers the result, so fill them in.

The results show five lines. Each gives the calories that fat should supply and the equivalent weight of fat per day:

• Maintain weight: fat for a day at your estimated maintenance calories.
• Lose weight: the same share applied to a budget that is 500 or 1,000 Calories lower (about 1 or 2 pounds, or 0.5 or 1 kg, a week by the labels).
• Gain weight: the same share applied to a budget that is 500 or 1,000 Calories higher.

The offsets are fixed round numbers and the weekly rates in the labels are approximate. A pound of body weight is commonly put at about 3,500 Calories (7,700 per kilogram), but real changes depend on how your body adapts, so treat each row as a starting point and adjust to what the scale does over several weeks.

If the planned budget is smaller than zero, which can happen for a very small, inactive person in a large-deficit row, the amounts come out negative. A negative line means that target is not realistic; use a milder row.

How the numbers are calculated

The calculator first estimates your resting energy use with the Mifflin-St Jeor equation, using weight in kilograms and height in centimetres, and then scales it by an activity factor to get your daily Calorie need.

BMR (men) = 10 × kg + 6.25 × cm − 5 × age + 5

BMR (women) = 10 × kg + 6.25 × cm − 5 × age − 161

daily Calories = BMR × activity factor

Fat supplies 9 Calories per gram, so once you know the Calories assigned to fat, grams follow by division:

fat Calories = daily Calories × fat share ÷ 100

fat grams = fat Calories ÷ 9 (ounces = grams ÷ 28.35)

Worked example. A 30-year-old man, 5 ft 10 in (177.8 cm) and 180 lb (81.6 kg), exercises lightly. His BMR is 10 × 81.65 + 6.25 × 177.8 − 5 × 30 + 5 = 1,783 Calories, and 1,783 × 1.375 gives about 2,451 Calories a day to hold his weight. At 25% fat that is 2,451 × 0.25 = 613 Calories from fat, or 613 ÷ 9 = 68 g (2.4 oz) a day. For the row that cuts 500 Calories, the budget is 1,951 and fat is 1,951 × 0.25 = 488 Calories, or 54 g.

Because the share is applied to the whole budget, eating less in total also lowers the fat figure in grams, even though the percentage stays the same.

How much fat do you need?

The US National Academies set an acceptable range of 20% to 35% of calories from fat for adults. Below the range it becomes hard to get enough essential fatty acids and fat-soluble vitamins (A, D, E and K); above it, there is less room for other nutrients and calories are easy to overshoot. Their adequate intakes for adults aged 19 to 50 are 17 g of linoleic acid a day for men and 12 g for women, and 1.6 g and 1.1 g of alpha-linolenic acid.

The kind of fat matters as much as the amount. The Dietary Guidelines for Americans advise keeping saturated fat under 10% of daily Calories, and the World Health Organization recommends total fat at or below 30% of energy, saturated fat under 10% and trans fat under 1%.

Dietary cholesterol is a separate matter. It occurs only in animal foods, and your liver makes cholesterol of its own. Recent US guidelines no longer set a numeric daily cap, but still advise eating as little as practical within a healthy pattern, which in practice means moderating foods that are also high in saturated fat.

These figures are estimates for healthy adults and not medical advice. Anyone with a medical condition, who is pregnant, or who is planning a large change in diet should talk to a doctor or dietitian first. See the disclaimer.

Fat in common eating patterns

Eating patterns differ mostly in how they split calories between carbohydrate, protein and fat. These are the splits behind the presets in the macro calculator, shown as the fat share:

Only the keto preset sits far above the 35% ceiling of the general guidance, so it is best discussed with a doctor or dietitian first. People who train hard are generally told to stay inside the 20% to 35% window too: going below 20% has not been shown to improve performance, and it can cut the intake of essential fats and fat-soluble vitamins.

Fat, Calories and weight

Fat is the most energy-dense nutrient, at 9 Calories per gram against 4 for protein and carbohydrate. A single tablespoon of cooking oil, about 14 g, carries roughly 120 Calories. That is why trimming added fats can lower intake quickly, and also why a handful of nuts or a generous pour of oil can quietly add a few hundred.

Weight change still comes down to total Calories. In a 12-month trial of 609 adults (the DIETFITS study), a healthy low-fat diet and a healthy low-carbohydrate diet produced similar average weight loss, with no statistically significant difference between them. Choose the fat share you can keep up, and put the effort into total intake and food quality.

To see what a fat target means alongside your protein and carbohydrate, use the macro calculator, or check the other two nutrients with the protein calculator and the carbs calculator.

Types of dietary fat

• Monounsaturated fat: olive and canola oil, avocados, most nuts. Swapping it in for saturated fat tends to lower LDL cholesterol.
• Polyunsaturated fat: sunflower and soybean oil, walnuts, seeds and oily fish. It includes the essential omega-6 and omega-3 fats your body cannot make.
• Saturated fat: butter, cheese, fatty meat, coconut and palm oil. Keep it below about a tenth of your Calories.
• Trans fat: mostly from partially hydrogenated oils. It raises LDL cholesterol and lowers HDL, so intake should be as low as possible.