Knowing how much load you can place into your pontoon boat is an essential thing to know, especially if you are planning on inviting more passengers on board than you would usually would do.
I’ve researched online for pontoon boat weight capacity charts and have never found anything entirely conclusive, so spent some time recently putting my own online pontoon boat weight calculator together which you can access below.
How to calculate buoyancy of a pontoon
It’s based on a very simplistic formula.
Pontoon Volume x Density of Water = Pontoon Weight Limit & Capacity
That’s essentially how it should work, but there will be some added factors you will need to consider. Above all, you should adhere to the government’s standards because if you do get stopped by the US Coast Guard, that’s what they will be looking at. You can find that information on their regulations page. They will have had scientists figuring out an exact method and weight limit for safety, so pay attention to what they say, not me.
This calculator is purely for fun and illustrative purposes only to give you an estimation on your pontoon boat weight capacity and weight limits.
Important Things to Note
- This calculator calculates figures based on the dimensions of just one single pontoon. This is important because one individual pontoon has to be able to take the entire weight of the boat and its contents.
- This calculation also bases its numbers on the basis that we have squared-off pontoons rather than cylindrical ones, so please do refer to your user manual.
- Once you have your calculation above, you will need to take into account how much the pontoon boat weighs and remove that from the final figure above.
- You will also need to subtract the weight of any modifications, equipment on-board, and your passengers.
Disclaimer: Please note that this calculator should not be considered 100% accurate, and you should consult your owner’s manual fully to make your final decision. It is for illustrative purposes only, based on my own online research into calculating pontoon boat weights and capacities.
Understanding the Maths & Forces Involved
There are three key forces at play when understanding how pontoon boats float, and why knowing your weight capacity and limits are very important. Those three factors are:
- Buoyancy: This is the upwards force that is exerted the two pontoons by the water.
- Displacement: This is the downward force of your pontoon boat. When stable the two should be the same.
- Volume: This is the physical space of your pontoon tubes.
How those all relate to each other is based on the Archimedes’ Principle which states that the upward buoyant force that is exerted on a body immersed in water will be the same as the weight of the water that the body displaces and acts in the upwards direction at the center of the displaced water.
I don’t blame you.
In simple terms we know that the weight of water is 62.4 lbs per cubic foot. So, a pontoon tube with a volume of 72 cubic foot will be able to support its own weight and also be filled with up to 4492.8 lbs before it eventually sinks.
We can see that theory at work using the calculation I referenced earlier:
Pontoon Volume x Density of Water (62.4 lbs) = Pontoon Weight Limit & Capacity
Using our real-world example, if your equal-sized pontoons have the individual dimensions of 18 x 2 x 2 feet (which is height x length x weight which equals volume) then you get 72 cubic feet of volume in one pontoon.
You then multiply the volume by the cubic weight of water. So, based on that, 72 x 62.4 gives you a weight limit capacity of 4492.8 pounds.
The reason we want just one of your pontoons to support the entire weight of the boat and its load is because, as you know, when you are out on the water, you can get pushed around. And there will be cases when just one of the pontoons will need to support all of the weight capacity at any one time.
Pontoon boats can be top-heavy, so it’s really important that when pontoon boats are designed, that each pontoon is able to support the whole weight of not just the boat, but also the entire load that’s inside of it.
Pontoon Weight Capacity Chart Limits: Conclusion
It’s important to understand and recognize that the weight and capacity calculator on this page is purely for ball-park purposes and should never be used to give you the definitive, legal, and safe answer to what your weight limits are.
Pontooning can be dangerous if you take risks and over-load your boat with additional weight and height.
Always consult your user manual, talk to the dealer and manufacturer, and consult the calculations for pontoon boats that can be found on the US Coast Guard website, so that you can stay as safe as possible, and always be on the right side of the law.
Handy Hint: I have also recently published a boat trailer weight chart with some basic calculations in it.