"If fish costs 3,000 yen per kg, using 100g means the cost is 300 yen."

With whole fish, this calculation often leads to discrepancies with your actual costs. That is because fish has non-edible parts not used in the dish, such as the head, bones, and internal organs.

To manage fish costs accurately, it is essential to calculate the food cost per plate by factoring in yield, rather than looking only at the purchase price per kilogram.

The basic process follows five steps: Price per kg → Yield rate → Usable portion unit cost → Cost per plate → Food cost percentage. In this article, we explain how to calculate and manage fish costs using concrete figures.

*The prices and yield rates below are illustrative examples to explain the calculation method. All prices exclude tax.

Think of Fish Cost Calculation in 5 Steps

Calculating in this sequence allows you to map out everything clearly from the initial purchase price to the food cost percentage of your finished dish.

1. Check the Price per Kg of the Fish

First, check the purchase price per kilogram. For example, suppose you purchased fish at 3,000 yen per kg.

3,000 yen ÷ 1,000g = 3 yen per gram

At this stage, that amounts to 300 yen per 100g. However, this calculation assumes that 100% of the purchased weight can be used in dishes. Because whole fish requires removing the head, bones, and viscera, we must factor in yield.

2. Calculate the Yield Rate

Yield rate refers to the percentage of the purchased fish that can actually be utilized for cooking.

Yield rate (%) = Usable weight ÷ Purchased weight × 100

If you prep a 1,000g whole fish and have 500g of usable portion left for dishes, the yield is: 500g ÷ 1,000g × 100 = 50%.

If you use the head and bones for stock or soup broth, you can allocate costs across different recipes. Here, for simplicity, we calculate with only the fillets used in the main dish as the usable portion.

3. Determine the Unit Cost of the Usable Portion

With a purchase price of 3,000 yen, a purchased weight of 1,000g, a usable weight of 500g, and a yield rate of 50%:

3,000 yen ÷ 500g = 6 yen per gram

Converted to a per-kilogram basis, this equals 6,000 yen.

The purchase price of the fish and the cost of the portion actually used on the plate are not the same.

4. Calculate the Food Cost per Plate

When Using 80g of Fish

If the usable portion cost is 6 yen per gram, then 6 yen × 80g = 480 yen. The cost of the fish used in one plate is 480 yen.

500g ÷ 80g = 6.25. In practice, this gives you 6 portions of 80g fillets, leaving 20g remaining. Whether that leftover portion is repurposed for another dish or thrown away will also affect your restaurant's overall food cost.

Add the Costs of Other Ingredients

In this example, the food cost per plate is 650 yen. For dishes that use frying oil or similar cooking fats, be sure to factor in the estimated amount consumed per serving as well.

5. Calculate the Food Cost Percentage per Plate

Food cost percentage (%) = Food cost per plate ÷ Selling price × 100

With a food cost of 650 yen and a selling price of 2,000 yen: 650 yen ÷ 2,000 yen × 100 = 32.5%.

Make sure to compare purchase costs and selling prices on the same tax basis. Standardizing on tax-excluded figures makes calculations much simpler and clearer.

Overview of the Calculations So Far

Whole Fish vs. Pre-processed Fish: Which Keeps Costs Lower?

Instead of comparing solely by the purchase price per kilogram, always evaluate with yield taken into account.

*Yield figures are hypothetical for illustrative purposes. For pre-processed fish, actual yield varies depending on whether pin bones are removed or fillets are pre-portioned.

Even when pre-processed fish carries a higher initial purchase price, the cost per usable portion can end up being lower. Make comprehensive purchasing decisions that consider processing fees, shipping costs, prep time, and waste loss.

Related article: "Whole Fish vs. Prepped Fish: Which Is More Cost-Effective? Comparing Purchase Price, Yield, Labor, and Waste"

6 Reasons Theoretical Costs Differ from Actual Costs

1. Additional loss during butchering and portioning

2. Inconsistent portion sizes per plate

3. Mistakes and trimming waste during kitchen prep

4. Spoilage and shrinkage due to declining inventory quality

5. Fluctuations in fish market purchase prices

6. Non-revenue usage, such as staff meals (makanai)

Even if a recipe specifies 80g per plate, serving 90g raises the fish cost from 480 yen to 540 yen. Over 30 orders, that adds up to an extra 1,800 yen.

Rather than relying only on theoretical spreadsheet costs, regularly check your actual usage and waste in the kitchen.

Distinguish Food Costs from Total Kitchen Operating Costs

Apart from food costs, operating a kitchen incurs labor, utilities, shipping, and consumables. While whole fish may have a lower food cost, it can demand significant prep time; pre-processed fish, conversely, can alleviate kitchen prep strain. Make strategic decisions by clearly separating food cost percentage from total operational cost.

7 Key Numbers to Record for Cost Management

Start tracking with your core menu items, and update your records whenever supplier prices or yields change.

Monthly Cost of Goods Sold = Beginning Inventory + Monthly Purchases − Ending Inventory

Combining per-plate recipe calculations with store-wide monthly COGS tracking gives you a cost management system that reflects real-world operations.

Frequently Asked Questions (FAQ)

Q. Can I calculate fish costs using only the price per kilogram?

With whole fish, you need to check the usable weight after eliminating the head, bones, and entrails in order to accurately determine the cost of the portion actually served to customers.

Q. What yield percentage should I use in calculations?

It varies depending on fish species, size, processing method, and the dish being prepared. It is best to weigh and record actual figures in your own kitchen.

Q. How do I calculate the fish cost for a single plate?

Divide the purchase price by the usable weight to find the cost per gram, multiply that by the portion weight per plate, and add the costs of any accompanying ingredients.

Q. What is the ideal food cost percentage?

There is no single correct target; it depends on your business format, price tier, and labor costs. Evaluate it alongside your gross profit per dish and overall restaurant earnings.

Q. Is pre-processed fish more expensive than whole fish?

Although the purchase price per kg is higher, factoring in the higher yield can reverse the difference. Always compare based on equivalent usable weight.

Summary | Shifting from "How Much Did It Cost?" to "How Much Does One Plate Cost?"

Managing fish costs follows five steps: ① Price per kg, ② Yield rate, ③ Usable portion unit cost, ④ Cost per plate, and ⑤ Food cost percentage.

Especially with whole fish, relying solely on invoice purchase prices can distort your actual costs. What matters most is understanding not just what you paid for the fish, but the true cost of serving each dish.

Related article: "How to Streamline Restaurant Seafood Procurement: 7 Points for Reviewing Ordering, Inventory, and Prep"

Making Seafood Procurement Simpler.

At FINE ATLAS, we look beyond the raw purchase price of fish to build new, restaurant-friendly procurement systems that support ordering, processing, inventory management, and kitchen prep.

Our goal is to deliver the exact fish you need, in the exact quantities you need, in formats that make work easier for chefs.

We help reduce kitchen prep workloads so culinary professionals can focus on what they do best: creating exceptional food.