Food labels often show fat per serving, but serving sizes vary wildly between brands and products. Comparing fat content across foods is much easier when you use a standard reference: fat per 100 grams. This calculator converts the fat content of any food to a per-100g value, whether your label shows grams, milligrams, or ounces and whether your serving is weighed in grams or ounces. It also estimates fat calories and the percentage of energy coming from fat using 9 kcal per gram.
Nutrition students, meal preppers, and anyone comparing packaged foods will find this handy. Enter the total fat and serving weight, pick your units, then calculate. An optional calories-per-100g field lets you see at a glance how much of a food's energy is fat. The result includes per-100g, per-ounce, and fat calorie breakdowns.
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How to Use This Calculator
Start by entering the total fat value from the nutrition label in the Total fat per serving field. Choose whether that number is in grams, milligrams, or ounces using the dropdown next to it. Then enter the serving size weight — the amount of food that the fat value refers to — and select grams or ounces. Most labels list both fat and serving size in grams, but the extra unit options help if you are reading an older label, a non-standard package, or a food database entry that uses ounces.
If you also know the food's calorie density in kcal per 100g, add it to the optional field. The calculator will then show fat calories per 100g and the percentage of the food's energy that comes from fat. Press Calculate to see the standardized result. The quick-fill buttons let you load common examples so you can see exactly how the tool behaves before entering your own numbers.
How the Calculation Works
Fat per 100g is a simple proportion:
Fat per 100g = (fat in serving ÷ serving weight) × 100
Before applying the formula, the calculator converts both values to grams. Milligrams are divided by 1000, and ounces are multiplied by 28.3495. For example, if a 30g serving of a snack contains 9g of fat, then fat per 100g = (9 ÷ 30) × 100 = 30g. If a label lists 0.32 oz of fat for a 1 oz serving, the calculator first converts to 9.07g of fat and 28.35g of serving weight, then computes (9.07 ÷ 28.35) × 100 = 32g per 100g.
Fat provides 9 kcal per gram. The optional calorie breakdown is therefore straightforward: fat calories per 100g = fat per 100g × 9, and the percentage is that value divided by the food's total energy per 100g, multiplied by 100. This is the same method used in nutrition labels and diet-tracking apps.
Fat per 100g in Context: Label Categories
Many regulatory schemes use per-100g thresholds to classify foods, which is one reason this metric is so useful for everyday label reading. The table below follows the UK/NI front-of-pack nutrition labelling scheme, one of the most widely cited systems.
| Category | Fat per 100g | Example foods |
|---|---|---|
| Low fat | ≤ 3 g | Skim milk, most vegetables, lean poultry |
| Moderate fat | 3 – 17.4 g | Whole eggs, salmon, avocados |
| High fat | ≥ 17.5 g | Nuts, butter, cheese, chocolate, oils |
Other countries use similar but not identical cutoffs, so always check the labeling rules in your region when using these words on product packaging.
Worked Examples
Example 1: Olive oil. A label shows 13.5g of fat per 14g serving. Fat per 100g = (13.5 ÷ 14) × 100 = 96.4g. This explains why oil is considered a high-fat food: it is almost pure fat by weight. If the oil provides 884 kcal per 100g, fat contributes 96.4 × 9 = 868 kcal, or about 98% of total calories.
Example 2: Cheddar cheese. 9.3g of fat in a 28g serving. Per 100g = (9.3 ÷ 28) × 100 = 33.2g. That places cheddar in the high-fat category, and if the cheese supplies 403 kcal per 100g, fat provides about 74% of its calories.
Example 3: Whole milk yogurt. 3.3g of fat per 100g serving. Per 100g = 3.3g, which sits just above the low-fat threshold. Small differences near the cutoff matter, which is why using your actual product label instead of a generic database entry is best.
Tips for Accurate Results
- Weigh foods in grams whenever possible. Volume-based nutrition values, such as per tablespoon or per cup, are less consistent because foods settle and pack differently.
- Use the same reference weight as the label. If the label gives fat per tablespoon but you weigh your serving, enter the weight of one tablespoon in grams to get an accurate per-100g result.
- For foods with multiple serving sizes, run the calculation for each if the fat content differs between them — for example, a mix with and without nuts.
- Remember that whole-fat dairy and other natural foods vary by brand, season, and animal feed. Prefer the label on the actual package you have.
- If the calories-per-100g field is missing, the main fat-per-100g result is still correct and useful on its own.
Dried, frozen, and ready-to-eat foods often list values for prepared or drained weights. Always check whether the serving weight is as sold or as consumed before entering it.
If you regularly track a particular ingredient, food-specific calculators can save time — for example, the whole fat per 100g calculator can be paired with precomputed pages like the beet fat per 100g calculator, the mustard fat per 100g calculator, or the salad fat per 100g calculator for those specific foods.
Frequently Asked Questions
What does whole fat per 100g mean?
Whole fat per 100g is another name for total fat per 100 grams of food. It includes all fatty acids present — saturated, monounsaturated, and polyunsaturated — expressed as a single number. This is the standard reference used on European nutrition labels and in most food databases.
Why use per 100g instead of per serving?
Serving sizes are arbitrary and differ between brands. Per 100g is a fixed, universal unit of comparison, so you can directly compare a cracker, a yogurt, and a sauce without mental math. It also lets you compute the fat in any amount you actually eat: just multiply the per-100g value by your portion weight in grams and divide by 100.
Does cooking change the fat per 100g value?
Yes. Cooking can remove water, render out fat, or add fat through oils and butter. Raw and cooked values are therefore often different. For example, a raw chicken thigh has a different fat-per-100g figure than a roasted one because water is lost and fat may drip away. Use values that match the form in which you are eating the food.
Is fat per 100g the same as fat percentage?
When both are measured by weight, yes. A food with 25g of fat per 100g is 25% fat by weight. The term becomes trickier when percentages on packaging refer to calories or to a daily value reference, so check the context of the label.
Can this help with keto, low-fat, or calorie-counting plans?
Absolutely. Keto dieters can use the per-100g value to choose foods that fit a high-fat macro target, while low-fat plans can quickly identify foods near or above the 17.5g high-fat threshold. For calorie counting, the fat-calorie breakdown shows how much of a food's energy is coming from fat versus carbohydrates and protein.