Catamaran Hull Speed Calculator For Beginners (Table and Free Spreadsheet)

Speed is important, it can get you out of harm’s way, and it makes sailing much more fun, but figuring out how fast a catamaran will be able to sail can be tricky. One important aspect is to understand maximum hull speed.

In this article, I have calculated different hull speeds for different lengths of boats; this includes both monohulls and catamarans but focuses on the latter. Here is the catamaran maximum hull speed table:

Catamaran Max Hull Speed Calculator Table

Length on Water		Displacement Max Hull Speed	Semi Planing Beyond Max Hull Speed
		0%	10%	20%	30%
Feet	Meter	Knots	Knots	Knots	Knots
26	8	6.9	7.5	9.1	11.8
30	9	7.3	8.0	9.6	12.5
33	10	7.7	8.4	10.1	13.2
36	11	8.0	8.8	10.6	13.8
39	12	8.4	9.2	11.1	14.4
43	13	8.7	9.6	11.5	15.0
46	14	9.1	10.0	12.0	15.6
49	15	9.4	10.3	12.4	16.1
52	16	9.7	10.7	12.8	16.6
56	17	10.0	11.0	13.2	17.2
59	18	10.3	11.3	13.6	17.7
62	19	10.6	11.6	14.0	18.1
66	20	10.8	11.9	14.3	18.6
69	21	11.1	12.2	14.7	19.1
72	22	11.4	12.5	15.0	19.5
75	23	11.6	12.8	15.3	20.0
79	24	11.9	13.1	15.7	20.4
82	25	12.1	13.3	16.0	20.8
85	26	12.4	13.6	16.3	21.2

Table Explanation

• Length on the waterline (L.W.L.): Length of the boat when measured on the waterline, not to be confused with length overall (L.O.A.), which is the boat’s total length (above the waterline) including bowsprit, etc.
• Displacement max hull speed: The max speed of a boat whose L.W.L doesn’t change when underway and where the vessel’s bow wave is the limiting speed factor.
• Semi/Light Displacement or Semi planing hulls speed: A boat where the bow waves speed limiting factors can be partially overcome and therefore exceed the displacement hull speed. These hulls usually overcome hull speed by 10-30%.

How to use the Catamaran Hulls Speed Table

1. Choose your length on waterline in the left-most column, either in feet or meter.
2. Continue reading to your right and stop either at “Displacement hulls speed” or continue to “10,20, or 30%”, depending on your estimated hull efficiency. This will be your calculated maximum hull speed for a semi-displacement catamaran.

The Formula

First of all, we need to know the maximum hull speed for a displacement hull, and from that number, we will be able to calculate how much faster the semi-planing (or semi-displacement) hull will be. This is the formula for Maximum Hull Speed on a displacement boat:

Max hull speed= √((Length on Water Line x g) /(2 x pi)) x 3600/1852

Now we need to add the increased efficiency (loss of drag) of a semi-displacement hull, usually, this is somewhere between a 10-30% increase.

Semi Displacement hull speed = Maximum hull speed * 1.3

Note: “1.3” is the increase in efficiency, if you believe you are on the lower end of the scale this would be 1.2 or 1.1.

How to Exceed Hull Speed

This calculator offers a theoretical perspective, but many other factors such as sail plan, weight, and sailor skill, of course, have a profound impact on speed. As we have seen, a semi-displacement hull can exceed maximum hull speed, but we can also see that it isn’t by much. The next step is to reduce drag even further by utilizing a planning hull.

If you want to better understand catamaran speed I suggest you read another one of my articles called Catamaran speed explained.

Catamaran Hull Speed Spreadsheet

If you want more info, calculate other lengths, or see the speeds in Km/h or Mph then I suggest you check out this free spreadsheet.

Catamaran Freedom Hull Speed Calculator

Note: If you want your own copy just click, File->make a copy.

Common Questions About Catamaran Hull Design

Below I will answer some of the questions I receive concerning catamaran hull design. The list will be updated as relevant questions come in.

Is a Catamaran a Planing hull?

As we have discussed above, a catamaran can definitely have a semi-planing hull, but can it be designed in a fully planing configuration as well?

Catamarans can be configured as planing hulls, although most sailing catamarans are set up as either semi-planing or hydrofoil. Due to the high speeds needed to get a boat to planing speed, this is only possible on racing sailboats or motor-powered catamarans such as high-speed ferries.