What is the Correct Way to Measure the Overall Length of a Boat?

what is the correct way to measure the overall length of a boat

For those studying for Boat Ed and the question on what is the correct way to measure the overall length of a boat pops up, then this is the guide for you.

Most boats have similar shapes and boating terms apply to most vessels you’ll encounter. So knowing these terms should make it easy for you to identify the right steps required to get the boat’s length.

Starting with the definition of the boat’s length which is defined as the length measured in a straight line from the tip of the bow (also known as the front of the vessel) to the tip of the stern (also known as the rear of the vessel). Any other attachments, extensions, fittings such as fishing lines, or handles, and outboard motors are excluded from this measurement.

Only the boat structure matters in this measurement and nothing else. That said, now that you know what classifies as the boat’s length, how are you supposed to measure it the correct way?

The Right Way to Do It

You’d think that measuring a boat will be a straightforward task right? Well, the problem is the sheer size of the boat compared to whatever measuring equipment you’ll use, not to mention the fact that you have to measure it in a straight line, thus using an extremely long tape measure around the hull of the boat will lead to inaccuracies. But to keep things simple, a tape measure will do.

For longer boats, additional manpower may be needed to maneuver the tape measure through the boat in as straight of a line as possible, as issues might arise from closed cabin boats, but for open deck ones, it should be easy enough for most people.

How To Do It In Detail

Here’s a simple step-by-step guide on the correct way of measuring boat length.

1. Get a Long Tape Measure

Get one that’s longer than your boat to account for any inconsistencies when having to maneuver through obstacles and more is usually better in this case.

2. Start From the Tip of the Bow

Start measuring from the tip of the bow right at the center. It helps if your tape measure end has some method of sticking to the tip so you could leave it there and proceed to the next step. However, if you can’t temporarily attach the tape measure end to the tip of the bow, hopefully, you have a friend that’ll help you out by holding it.

3. Proceed Slowly and Carefully Towards the Stern

On most open deck boats and pontoons, this isn’t an issue as the deck usually has a path straight from the bow to stern.

However some boats might have windshields in the way or even full-sized cabins, so some maneuvering and dexterity will be required. Don’t be in a rush and just slowly proceed towards the stern and the next step.

4. Ensure that the Tape Measure is Straight

Now that you’re on the stern, make sure that you have as direct of a line of sight towards the bow as possible, and keep the tape measure as straight as you can.
Now you can measure the length.

Why It's Important to Know a Boat's Length?

After reading through this guide and going through the steps, why do we even bother measuring the boat’s length, can’t we just ask a manual regarding the boat’s specifications and derive the overall length from there?

Well sure you could do that, but how far can you really trust a piece of paper compared to what your eyes can see, right?

Also, some manufacturers measure overall length differently, so to be doubly sure of your boat’s length you might as well do it yourself.

Why You Would Need to Know It?

The quick answer is for both practical and legal reasons.

Practically speaking you’re going to need the length so you know whether or not your boat will fit your trailer, or for other transportation costs. Length is also an important factor when measuring up an anchor chain, and also for calculating vessel accommodation costs on a marina or dock.

Since boats are divided into classes A, 1, 2, and 3, with lengths measuring less than 16ft, 16ft to less than 26 ft, 26 ft to less than 40 ft, and 40ft to less than 65 ft, for legal purposes and compliance with your local regulations and boating laws, you’re also going to need that length measurement for transportation regulations as your highways may not allow your boat and trailer to travel on it depending on the day and time.


Rudders, outboard motors, and motor brackets, handles, ladders, fittings, attachments such as rods for fishing, and other extensions. You need not worry about your outboard motor size especially when upgrading. Swimming platforms for inboard motorboats are included in estimating the length.

As the overall length only measures the immediate boat you are in, towing skis, wakeboards, kayaks, or other external watercraft and watersports equipment are not included in the overall measurement as they are not technically a part of the boat.


In summary, measuring a boat’s length isn’t too difficult as long as you always measure from the tip of the bow at the centerline, all way down to the stern. You just need to be aware of the straightness of the tape measure at all times and making it a two-man job makes things significantly easier than doing everything solo.

The only truly confusing thing regarding measuring a boat’s length aside from the physical effort required, is the exceptions section of this guide, as you need to remember exactly which part of the stern you should stop your measurement.

With all that said and done, whenever this question pops up on a Quizlet or boat ed know you have an idea on what is the correct way to measure the overall length of a boat.

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