Estimate how many grams of dietary fat to eat each day from your age, sex, height, weight, and activity. Switch US and metric units, pick Mifflin St Jeor or Katch-McArdle, and see calories plus a 20–35% fat range, saturated-fat caps at 10% and 7%, and lose- and gain-weight rows.
Formula
Calories start with basal metabolic rate (BMR), then an activity factor. Mifflin St Jeor (the default) uses kilograms (W), centimetres (H), and years (A). Katch-McArdle uses lean mass from body-fat fraction (bf):
Men: BMR = 10W + 6.25H − 5A + 5
Women: BMR = 10W + 6.25H − 5A − 161
Katch: BMR = 370 + 21.6 × W × (1 − bf)
Calories = round(BMR × activity)
Fat g = round(calories × percent ÷ 8.8)
The highlighted range is 20–35% of calories. Saturated-fat caps use the same rounding at 10% (general) and 7% (heart-disease reduction). Goal rows assume about 3,500 calories per pound: 0 (maintain), ±500 (1 lb / 0.5 kg per week), ±1,000 (2 lb / 1 kg).
| Activity level | Factor |
|---|---|
| Sedentary (little or no exercise) | 1.2 |
| Light (1–3 times/week) | 1.375 |
| Moderate (4–5 times/week) | 1.465 |
| Active (daily, or intense 3–4 times/week) | 1.55 |
| Very Active (intense 6–7 times/week) | 1.725 |
| Extra Active (very intense daily, or physical job) | 1.9 |
Fat intake by age (share of total calories):
| Age | Suggested fat intake |
|---|---|
| 2 – 3 | 30% to 40% |
| 4 – 18 | 25% to 35% |
| 19+ | 20% to 35% |
Exercise here means 15–30 minutes of elevated heart rate. Intense exercise is 45–120 minutes; very intense is 2+ hours.
These numbers are typical-situation estimates. If you are an athlete, pregnant, or on a medical diet, ask a doctor or registered dietitian before changing how you eat. Very low calorie intakes should only be used under medical supervision.
Different types of fat
Fat is one of three macronutrients, with carbohydrate and protein. It supplies energy, helps absorb vitamins A, D, E, and K, and is part of every cell membrane. A little unsaturated fat is useful; extra calories from any fat still add up.
Saturated fat is common in fatty meats, poultry skin, and many dairy foods, and also shows up in some tropical oils, nuts, and seeds. Guidance from groups such as the American Heart Association treats it as a fat to keep modest, because higher intakes tend to raise LDL cholesterol.
Trans fat occurs in tiny amounts in some animal foods, but most of what people eat comes from partial hydrogenation. It raises LDL, lowers HDL, and has no known benefit. A label can say 0 g trans fat if a serving has less than 0.5 g — check the ingredients for “partially hydrogenated.”
Monounsaturated and polyunsaturated fats (olive oil, nuts, seeds, many plant oils, and omega-3s in some fish) are the usual swaps for saturated fat in a heart-conscious pattern.
Daily fat intake
There is no single perfect gram target. Children need some fat to grow — whole milk is often suggested after breastfeeding, unless a clinician says otherwise. For adults, practical habits look like:
- Keep saturated fat under 10% of calories; 7% is a common tighter cap when heart-disease risk is a concern.
- Prefer unsaturated fats when you replace saturated fat.
- Minimize trans fat.
- Dietary cholesterol is often kept under 300 mg per day.
Examples
Man, 25, 5 ft 10 in, 160 lb, light activity
Mifflin St Jeor at light activity (1.375) is 2,361 Calories/day. Fat at 20–35% is 54 – 94 g/day. Saturated fat is under 27 g (10%) or 19 g (7%). Lose 1 lb/week is 1,861 Calories (42 – 74 g fat); gain 1 lb/week is 2,861 Calories (65 – 114 g).
Woman, 30, 5 ft 4 in, 140 lb, light activity
Female Mifflin at the same activity is 1,843 Calories/day, or 42 – 73 g of fat, with saturated fat under 21 g / 15 g.
Metric default, 180 cm, 60 kg
The same age-25 male at light activity in metric units is 2,207 Calories/day, 50 – 88 g of fat, with kilogram weekly lose/gain labels (0.5 kg and 1 kg per week).