Wondering how fast a boat can go? Confused by all the boat speed terms out there, like knot and nautical mile per hour? Use our calculator to convert knots to miles/hour, get an estimated theoretical maximum speed for your boat, plus estimate its trim and how far it will travel in a certain amount of time.

What is a boat?

A boat (also called a vessel) is a human-powered or motorized watercraft used for transport or recreation. There are many types of boats, ranging from canoes to cruise ships. Boats were invented by humans, who first made logs and pieces of wood into watercraft to cross rivers and lakes. The oldest known boats date back to 8,000 years ago in Africa

What is boat displacement?

The weight of the water displaced by a vessel is its displacement. Displacement is measured in tonnes and not pounds, which might seem confusing at first, but you’ll get used to it. When we say that a boat has a displacement of 10 tonnes, we’re saying that if this boat were placed in open water with no other boats around, it would displace 10 tonnes of water.

What is the crouch constant?

The Crouch constant is a numerical value that is used in the boat speed formula to calculate the speed of a boat. It was named after naval architect David Crouch, who first used this specific type of constant in his calculations. This particular constant is used when calculating how fast a ship travels through water based on its hull design and size.

Boat speed units

The boat speed calculator can convert your speed from one unit to another. Here are the units it supports:

  • Knots (nautical miles per hour) – 1 knot = 1.852 kilometers per hour, 0.514 meters per second or 0.5144 miles per hour (1 mile is equivalent to 1760 yards).
  • Kilometers/hour – 1 kilometer is equivalent to 0.62137 miles or 3281 feet and 35 seconds, which makes it easy to do conversion calculations with a simple mental trick: multiply by 1000 (1000m = 1km), then add 3280ft or 5 feet for every third meter; this will give you an approximate answer that you can round up or down as needed with no problem whatsoever
  • Miles/hour – You can also use this calculator with your favorite imperial units like kilometers/hour but if that doesn’t work out well for you then don’t worry because both km/h & mph numbers have their own individual units within the same system where they belong

How to use the boat speed calculator

The boat speed calculator can calculate the top speed on your boat based on its:

  • Type
  • Shaft horsepower
  • Displacement

There are 9 types of boats:

  • Cruisers
  • Passenger vessels
  • Average runabouts
  • Light high-speed cruisers
  • High-speed runabouts
  • Racing boats
  • Hydroplanes
  • Racing catamarans
  • Sea sleds

The formula also involves the Crouch’s constant, which is 150. Once all values are input, the calculator can give you the theoretical top speed of the boat.


What is a boat?

A boat (also called a vessel) is a human-powered or motorized watercraft used for transport or recreation.

What is the fastest boat?

The Spirit of Australia is generally considered to be the fastest boat.

What determines boat speed?

Boat speed is determined by the boat type, boat displacement, and horsepower.