How many grams are in a piece of fish?

December 13, 2025 •

4 min read

According to the National Health Service (NHS), a recommended portion of fish is around 140 grams, but this can vary significantly. The precise number of grams in a piece of fish depends on several factors, including the type of fish, the cut, and whether it's a standard serving size or a full fillet.

Quick Summary

The mass of a fish portion varies greatly depending on the species and cut. Standard serving sizes range from 100g to 170g, with raw or cooked weight being a key distinction. Factors like preparation and dietary needs also influence the ideal quantity.

Key Points

Standard Portion Size: A common dietary guideline suggests a cooked serving of about 140 grams.
Type and Cut Matter: The weight of a single piece varies significantly with the species and cut, such as a thicker tuna steak versus a delicate sea bass fillet.
Raw vs. Cooked Weight: Cooked fish weighs less than raw fish due to water loss, a key detail for accurate dietary tracking.
Estimate Without a Scale: For a quick estimate, a 140-170g portion is roughly the size and thickness of an adult's palm.
Nutritional Calculations: Many nutritional labels use an 84-gram (3-ounce) cooked serving for comparison, so check the label for context.
Consider Preparation: Whether the fish is bone-in or boneless, and skin-on or skinless, will impact its final weight.

Understanding the Standard Fish Serving

The question of "how many grams are in a piece of fish" is not a simple one, as the answer varies depending on who you ask and what type of fish you're talking about. In many countries, dietary guidelines provide recommendations for what is considered a standard portion. For instance, the UK's NHS suggests a cooked portion of around 140g, which is a useful benchmark. However, other organizations, like the Washington State Department of Health, offer guidelines based on body weight, recommending roughly 8 ounces (227g) of uncooked fish for a 160-pound adult.

Factors That Influence Fish Portion Size

Several factors contribute to the weight of a single piece of fish, moving beyond the simple 'one size fits all' assumption.

Type of Fish: Different species naturally come in different sizes. A tuna steak is typically thicker and denser than a cod fillet, resulting in a higher weight per piece.
Cut of Fish: A fish fillet, which is a side of the fish cut away from the backbone, will weigh differently than a loin, which is the best part of the fillet from a larger fish like cod or tuna.
Cooked vs. Raw Weight: When fish is cooked, it loses water, which reduces its weight. A 170g (6 ounce) raw piece of fish, for example, will weigh less after it has been cooked. Nutritional information is often based on the cooked weight.
Preparation: Skin-on or skinless, bone-in or boneless—these factors also affect the final weight. A whole sea bass, for instance, includes the weight of bones and head, while a fillet does not.

Common Fish Types and Their Typical Portion Weights

Here is a list of common fish types and their approximate weights for a single serving, based on commercial and health recommendations:

Salmon Fillet: A single portion is typically between 120 and 150 grams. Some providers offer larger sides of salmon for family meals.
Cod or Haddock: A standard portion for a fillet or loin is often around 150 grams.
Tuna Steak: A thick tuna loin steak can range from 150 to 220 grams per piece, depending on the cut.
Sea Bass Fillet: A single fillet for a person is often smaller, around 110 grams.
Halibut Supreme: Portions of halibut cut from a larger fillet are commonly 150 grams.

Comparing Different Cuts and Weights

To help visualize the difference in standard portion sizes, consider the following comparison table. This table shows approximate raw weights and how they might differ for various fish types and cuts.


Fish Type	Cut	Typical Raw Weight (grams)	Notes
Atlantic Salmon	Fillet Portion	120–150g	Standard serving, boneless.
Yellowfin Tuna	Steak	150–220g	Steaks are typically thick and dense.
Atlantic Cod	Loin	150g	Thickest part of the fillet.
Sea Bass	Fillet	110–120g	A smaller, lighter fillet.
Whole Fish	Sea Bass	400g+	Includes bones, head, etc., for a single serving.

Practical Tips for Measuring and Estimating

Without a kitchen scale, estimating the grams in a piece of fish can be challenging, but it's not impossible. A good rule of thumb is to use the palm of your hand as a guide. A standard serving of around 140-170 grams (5-6 ounces) is roughly the size and thickness of an adult's palm. Keep in mind that different fish species have different densities, so this is just a rough estimate.

For more precision, consider a dedicated kitchen scale. Digital scales are widely available and relatively inexpensive, offering a quick and accurate way to measure your portions for dietary tracking or recipe adherence. If you're out fishing, formulas can be used to estimate a fish's weight based on length and girth, although this is for the whole fish and not a single piece.

Nutritional Information and Serving Sizes

Understanding the weight of a fish portion is also crucial for calculating nutritional intake. The FDA and USDA provide nutritional data, often based on a standard 3-ounce (84-gram) cooked serving, which allows for consistent comparison across different types of fish. For example, a 100-gram serving of Atlantic cod provides around 82 calories and 18 grams of protein, while the same amount of Atlantic salmon provides roughly 200 calories and 24 grams of protein, due to its higher fat content.

Conclusion

Ultimately, how many grams are in a piece of fish is a question with a variable answer. A standard healthy portion is typically between 140 and 170 grams, though this figure is highly dependent on the fish species, cut, and preparation method. For accurate dietary planning, always consider whether the weight is for a raw or cooked portion and use a kitchen scale for precision. For general estimates, the palm-of-your-hand rule provides a reliable, non-technical shortcut. Understanding these nuances helps ensure you're getting the right amount of seafood in your diet while cooking with confidence.

Food and Drug Administration: Nutrition Information for Cooked Seafood

Frequently Asked Questions

A standard single serving of cooked fish is generally considered to be around 140 grams (or about 5 ounces). For uncooked fish, a standard portion might be slightly larger, around 170 grams (6 ounces), to account for water loss during cooking.

Yes, the type of fish significantly affects its typical serving size. For example, a nutrient-dense and larger cut like a tuna steak can be around 150-220 grams per portion, while a leaner fish like sea bass might be a smaller, 110-gram fillet.

You can estimate a serving of fish by using the palm of your hand as a guide. A 140-170 gram portion is typically equivalent to the size and thickness of an average adult's palm. For recreational fishers, there are formulas based on a fish's length and girth to estimate its total weight.

Cooked fish weighs less than raw fish because water evaporates during the cooking process. This is a crucial factor to remember when measuring portions for nutritional purposes, as dietary guidelines often specify whether the weight is for a raw or cooked serving.

A standard individual portion of a salmon fillet is typically between 120 and 150 grams, though larger fillets are often sold for family-style meals.

An 84-gram (3-ounce) cooked serving is the standard reference size used by the FDA for nutritional labeling, which allows for easy comparison across different types of seafood. While it provides a nutritional baseline, it is a smaller portion than many recommended single servings for a meal.

Yes, for bone-in or skin-on cuts, the weight of the bones and skin is included in the total mass. When preparing a whole fish, this can add significant weight compared to a boneless, skinless fillet.