Different species have different body density formulas.
Measure from the nose to the fork of the tail.
Please enter a valid length greater than 0.
Measure around the thickest part of the body. If empty, we will estimate it.
Please enter a valid girth greater than 0.
Estimated Weight
0.00lbs
Est. Girth Used
–
Condition Factor (K)
–
Est. Fillet Yield
–
Formula Used: Standard Sturdy's Formula (Weight = Length × Girth² / 800)
Length vs. Weight Growth Curve
Reference Weight Table (Atlantic/Standard)
Length (in)
Avg. Girth (in)
Est. Weight (lbs)
Est. Weight (kg)
Table 1: Estimated weights for salmon based on standard length-to-girth ratios.
What is a Salmon Weight Calculator?
A salmon weight calculator is an essential tool for anglers, fisheries biologists, and conservationists who need to estimate the weight of a fish without using a scale. This is particularly crucial for catch-and-release fishing, where minimizing the handling time and stress on the fish is paramount. By measuring just the length (and optionally the girth) of the fish, you can derive a highly accurate weight estimate using established biological formulas.
Using a salmon weight calculator allows you to release the fish quickly back into the water while still obtaining the data needed for bragging rights or personal records. Unlike generic fish calculators, a specialized salmon weight calculator accounts for the specific body density and shape of salmonid species, such as Chinook (King), Coho (Silver), and Atlantic salmon.
Salmon Weight Calculator Formula and Explanation
The most widely accepted method for calculating the weight of a salmon is Sturdy's Formula. This mathematical model approximates the fish's volume as a cylinder and applies a specific density factor.
The Core Formula
Weight (lbs) = (Length × Girth²) / Divisor
Where:
Length: Measured in inches, usually from the tip of the nose to the fork of the tail.
Girth: Measured in inches at the thickest part of the fish (usually just ahead of the dorsal fin).
Divisor: A constant that changes based on the species and condition of the fish.
Variables Table
Variable
Meaning
Unit
Typical Range
L
Fork Length
Inches
15 – 50+ in
G
Girth
Inches
10 – 35+ in
D
Divisor
Constant
750 – 850 (Species dependent)
Table 2: Key variables used in salmon weight calculations.
Practical Examples
Example 1: The Trophy Chinook
Imagine you catch a large Chinook (King) salmon. You quickly measure its length at 40 inches and its girth at 24 inches. Using the salmon weight calculator with a divisor of 760 (typical for robust Chinook):
You catch an Atlantic salmon measuring 32 inches but don't have a tape measure handy for the girth. The calculator estimates girth based on standard ratios (approx. 55-60% of length). Let's assume an estimated girth of 18.5 inches and a standard divisor of 800.
Select the Species: Choose the specific type of salmon you caught. Different species (e.g., Pink vs. King) have different body shapes, which affects the formula divisor.
Enter Length: Input the length in inches. Ensure you measure from the snout to the fork of the tail for best accuracy.
Enter Girth (Optional): If you measured the girth, enter it. If you leave this blank, the salmon weight calculator will estimate it for you based on average biological data.
Review Results: The tool instantly displays the estimated weight, along with a "Condition Factor" which indicates if the fish is lean or robust for its length.
Key Factors That Affect Salmon Weight Results
While the salmon weight calculator is highly accurate, several biological and environmental factors can influence the actual weight of the fish versus the calculated weight.
Spawning Phase: Salmon stop feeding when they enter freshwater to spawn. A fish caught late in the spawning run will weigh significantly less than a fresh "chrome" fish of the same length due to fat reserve depletion.
Gender: Male salmon (bucks) often develop a kype (hooked jaw) and a humped back, which can distort length and girth measurements compared to females (hens).
Stomach Content: A salmon actively feeding in the ocean may have a stomach full of baitfish, adding temporary weight that the length/girth formula cannot account for.
Measurement Error: Measuring a slippery, moving fish is difficult. A 1-inch error in girth has a squared effect on the result, causing a larger deviation than a 1-inch error in length.
Region/Stock: A Kenai River King salmon is genetically different from a Columbia River King. Regional stocks often have distinct body shape ratios.
Fillet Yield: The total weight includes head, guts, and fins. The "Est. Fillet Yield" in our calculator helps you understand how much edible meat you might expect (typically 55-60% of total weight).
Frequently Asked Questions (FAQ)
1. How accurate is this salmon weight calculator?
For most fish, this calculator is accurate within ±10%. It is generally more accurate than a cheap spring scale, which can rust or stick.
2. What if I only have the length?
The calculator has a built-in regression model to estimate girth based on length. While not as precise as measuring both, it provides a very close approximation for average-conditioned fish.
3. Can I use this for Trout or Steelhead?
While similar, Steelhead and Trout often require a divisor of 800 or higher as they are generally more slender than mature ocean-run salmon. Check our related tools for a specific trout calculator.
4. What is the "Condition Factor"?
The Condition Factor (K) measures the "plumpness" of the fish. A K-factor of 1.0 is standard. Higher than 1.0 means a fat fish; lower means a lean or post-spawn fish.
5. Does this work for landlocked salmon?
Yes, but landlocked salmon (like Kokanee) are often smaller. The formula holds mathematically, but ensure your measurements are precise.
6. Why is the divisor different for Chinook?
Chinook (King) salmon are generally thicker across the back than other species. A lower divisor (e.g., 760 vs 800) results in a higher calculated weight, reflecting this bulk.
7. Should I measure to the tip of the tail or the fork?
Always measure to the "fork" of the tail. The tips of the tail can be frayed or uneven, making Fork Length the standard scientific measurement.
8. Is this calculator legal for tournaments?
Most catch-and-release tournaments have their own official conversion charts. You should always use the specific chart provided by the tournament organizers.