How To Measure A Fish - The Ultimate Guide To Measuring A Fish Correctly And Tool Recommendations To Help


An accurate measurement of a fish that has been caught is very useful for both anglers and scientists for different reasons. Typically, an angler will measure a fish to ensure it’s big enough to take home or to keep a record of their catches. Scientists will use measurement data to keep a record of the growth of different fish species. It is always important to note that when measuring a fish, it should be laid down flat on top of a measuring tape or ruler. Alternatively, there are safe measuring stickers to use that helps to measure fish with ease. This article will aim to provide you with the correct measurements of a fish, how to accurately measure them and some tools/product to help you with the measuring. 

Rules Number 1;  Reasons Behind Measuring A Fish

As a beginner angler, you may ask yourself, why do other anglers actually measure a fish? Well, there are certain reasons and rules to why they do. 

> Required as per certain laws (Regulations of Fishing)
> Scientific research & experiments
> Pro anglers measuring during competitions
> Attempting to break world record catches
> Making A Personal Record on Weights & Lengths of Catches

Rule Number 2; Understand and Know the Regulations of Measuring A Fish

> What Kind of Measurements Are You Aiming To Use? Understand The Different Types of Fish Measurements Before Carrying Them Out (See Below For More Details)
> Ensure You Know The Local Minimum & Maximum Fish Measurement Regulations
> Do You Need To Squeeze The Tail? That really depends on your local rules and regulations. Many scientific researchers do not but most local authorities require you to do so. Check before you head out to the water. 
> Ensure you have an accurate measuring tool to get a good reading (see below for some recommendations). 

Role Number 3; Use Precautionary Measures When Measuring The Fish

> It is important that your hands are slightly wet before handling and measuring your catch. This will prevent damaging the special mucous membranes that lie on the outside of the fish. 
> When possible, you should try to avoid using a net to bring your fish to shore - especially if you’re planning on releasing the catch. 
> Be prepared! - Ensure you have all measuring equipment ready and easily accessible, as well as any other equipment needed once the fish is out of the water. This ensures the measuring process is quick and the fish can be put back in the water as soon as possible. 

How To Measure A Fish Accurately? 

The photos below will help you to understand how to measure a fish correctly. To get the perfect measurement, ensure the mouth is closed and the tail is pinched. To measure specific parts of the fish, see the description below which gives more information about how to do so. 

Head Length


The head length is measured from the edge of the mouth/snout, whichever is more anterior to the body (furthest away from the body) to where the gill plate meets the body, see photo above for reference. 

Snout Length


The head length is measured from the edge of the mouth/snout, whichever is more anterior to the body to the beginning of the eye, see photo above. 

Body Depth:


The body depth is the maximum distance and not the body's girth. It measures from the top to the bottom of the fish’s body, excluding the fins. See photo above. 

Body Girth:


This is the circumference around the fish’s body. See photo above for an example of measurement.

Total Length: 


Beginning the measurement at the start of the fish’s mouth/snout to the back end of the fish, including the caudal fin. See photo above for an example. 

Fork Length:


Similar to total length, however in this case the fork length measures from the snout/mouth to the back end of the fish (start of the caudal fin). See photo for more info. 

Standard Length:


Excluding the caudal fin, this measurement is taken from the fish’s snout/mouth to the back end of its body. See photo above for reference. 

Fishing Measuring Rulers, Stickers & Tools

Frabill 1556 Bump Board 

The Frabill 1556 Bump Board Allows for a quick measurement after a catch, meaning the fish’s time out of the water is at a minimum. Made of gold-anodized aluminium ensures it is long-lasting and durable. 

Frozen Lines Fishing Rod Decal

Our very own rod decal sticker will allow you to measure your fish up against your rod. No need to have to remember your fishing device as this will permanently be stuck on your rod throughout the year. The sticker measures at 36”x0.4” and there are numbers at every 1 inch increments. Click the link to purchase now on amazon or buy here at 

YakGear Fish Stik 

This folding fish ruler is 12 inches when stowed and 36inches when expanded. Because the ruler folds, it is easy to store and carry around when fishing. Available in yellow, white and orange. 

Frozen Lines Fish Measurement Sticker

Another one of our stickers, this time it is perfect to be stuck on the side of a kayak, boat or along the handle of your landing net. Slightly larger than the rod decal, measuring at 36” x 1”, this measuring sticker is an excellent fish measuring board alternative. Click the link above or buy now here at

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