Hull Speed Calculator

A Hull Speed Calculator is a simple online tool that helps you figure out the fastest speed your boat can travel without rising out of the water. This speed is called the hull speed. It’s based on the length of your boat at the waterline. Whether you're sailing, cruising, or just curious, this calculator shows you the most efficient speed your boat can travel without using extra fuel or energy.

We developed this calculator so that anyone from beginners to seasoned sailors can quickly find their hull speed without doing complicated math.

How Does Hull Speed Work?

Hull speed is a common concept in boating. It refers to the point at which a boat's speed creates a wave equal to the boat's waterline length. At this point, the boat starts climbing its own wave. Going faster becomes difficult unless the boat is designed to plane on top of the water.

The hull speed is most accurate for displacement hulls (like most sailboats and catamarans), but it also helps estimate performance for semi-displacement and planing hulls.

Hull Speed Formula (in Plain Words)

Here’s the basic formula:

Hull Speed (knots) = 1.34 × √LWL

Where:

• 1.34 is a constant,
• √LWL means the square root of the length of the waterline in feet.

So if your boat has a waterline length of 30 feet:

Hull Speed = 1.34 × √30 ≈ 1.34 × 5.48 ≈ 7.34 knots

This means your boat’s most efficient speed is around 7.34 knots.

How to Use Our Hull Speed Calculator

Using our Hull Speed Calculator is super simple:

1. Enter your boat's waterline length (LWL). You can choose between feet or meters.
2. Click the Calculate button.
3. Instantly see your boat’s hull speed in knots.

You don’t need to know math or use any formulas the calculator does all the work for you.

It works for:

• Sailboats
• Catamarans
• Semi-displacement boats
• Planing hull boats (with estimated performance limits)

Our tool is also mobile-friendly and fast, making it easy to use on your phone or tablet.

Why is Hull Speed Important?

Knowing your hull speed helps you:

• Save fuel or battery power
• Avoid pushing your boat too hard
• Plan efficient sailing or cruising routes
• Understand your boat's performance limits

Trying to go faster than your hull speed without the right hull design uses a lot more energy. It’s like trying to run through deep water it takes more effort than it’s worth.

Final Verdict

The Hull Speed Calculator is an essential tool for any boat owner or marine enthusiast. It tells you how fast your boat can efficiently travel based on its waterline length. With just a few clicks, you’ll know your boat’s performance limits, avoid fuel waste, and enjoy a smoother, more efficient ride.

Our calculator supports multiple hull types, including sailboats, catamarans, and semi-displacement boats, making it perfect for all kinds of boaters.

Common Questions About Hull Speed

What is the hull speed of a 30 foot boat?

Using the formula:

Hull Speed = 1.34 × √30 ≈ 7.34 knots

A 30-foot boat with a full displacement hull would have a hull speed around 7.34 knots.

What happens if you exceed hull speed?

If you go faster than your hull speed in a displacement boat, your boat will push a bigger wave and require a lot more power to gain small speed increases. You’ll burn more fuel or battery and stress the engine, with little benefit.

What is the most efficient hull speed?

The most efficient hull speed is slightly below your calculated hull speed. Operating at 90%–95% of hull speed gives the best fuel efficiency and smoothest ride.

Can a catamaran exceed its hull speed?

Yes, some catamarans have slender hulls that allow them to go faster than their hull speed. However, hull speed is still a good reference point for understanding basic efficiency.

How do you calculate hull speed in metric?

If your boat's waterline is in meters, convert it to feet first:

1 meter = 3.28084 feet

Then use the same formula:

Hull Speed (knots) = 1.34 × √(waterline length in feet)