This is the latest version of the Sail Calculator (3.55). Report any problems to Tom Dove.

*Please submit boat data with the "SUBMIT DATA" button at the end of Part I.

Carl Adler died on November 17, 2013.
The sailing community has lost a valuable crewmember and a fine man. Tom Dove will continue to host Carl's Sail Calculator on his Web site; please direct correspondence to him.

Carl Adler
Welcome to
Carl's Sail Calculator v3.55.

For multihulls, try this site
This page works with all standard browsers on Mac OSX, Windows 7 or later, and Linux. It does not render properly on Apple iPads and iPhones running iOS 10. This is an OS problem beyond my control.

You can use the Sail Calculator to look up sailboat dimensions in a large database of boats or enter your own boat's dimensions and compare it to the others. In addition, for any boat you can calculate a set of values that will help you measure how it will perform.

Some data were moved and recalculated from earlier versions. If you find any basic measurements that you know to be incorrect for any of the boats please send the corrections to Tom.

Choose View Source in your browser for acknowledgements and open source statement.

Some text and layout revisions by Tom Dove. This version was last modified on and contains boats.

Part 1, Select A Boat From The Database: When you select a boat, its parameters appear below in Part 2.
Choose a type of boat:
All Boats Cruisers Racers Racer/Cruisers Cruiser/Racers
Select one boat in each column above, and press to compare.

Part 1B, Enter Measurements For Your Boat: Note that length overall, length of waterline, and beam are in feet, displacement in pounds, and sail area in square feet. Do not use , ' or " in your numbers, which should be in the form, for example, 1000.50. Note that this site uses the American standard, with a period instead of a comma as a decimal delineator.
!You can enter your values in metric units (meters, square meters, and kilograms), if you follow each number entered with the letter "m" and then click on the page anywhere outside the entry box. Doing this will convert each of your entries to the native units (feet, square feet, and pounds0) used by the calculator. Thus if you enter 1000m for the displacement in kilograms, it will be converted to 2204.6 pounds.
Boat Name (e.g., Hunter 33.5):
Hull Length or
Length on Deck (LOD)
LWL Beam Disp Sail Area:
Main plus
100% Fore Triangle*
*One-half the vertical distance from the deck to the point on the mast where the jib sail attaches multiplied by the horizontal
distance from the base of the mast to the bow.
Press to see the derived quatities displayed below in Part 2.
Click SUBMIT DATA to e-mail the data on your boat to Tom:

Part 2, Results: This area displays the parameters of the boat selected. Do not enter values here. Click on any of the Derived Quantities boxes for an explanation of the box.
Basic measurements
LOA LWL Beam Displacement Sail Area
Derived quantities. (Click on each box for an explanation in the box below.)
Displacement to LWL Hull Speed Sail Area to Displacement
LWL to Beam Motion Comfort Capsize Ratio
Sailing Category Pounds/Inch

After using the "compute" button send the full report to a friend's email address: by clicking here:

Part 3, Search Database: You can search for boats in the database you selected in Part 1 by their parameters. Select any number of conditions.
Find all boats which have >
and >
and >
and >
and >

Part 4, Find Your Ideal Boat: You can find your 'ideal' boat by doing a weighted search. For example, you can search for the boat that has the highest combined normalized scores in 'Motion Comfort' and 'Sail Area to Displacement' giving one a 60% weight and the other 40%, or whatever! You can also do low searches, for example, you can search for the boat that has the highest normalized score in 'Motion Comfort' and the lowest normalized score in 'Capsize Ratio' giving one a 30% weight and the other 70%, or whatever. A 'high' search is done as a percentage of the highest boat in the parameter. So, if the boat with the highest Sail Area to Displacement has a value of 48, a boat with a Sail Area to Displacement of 24 would receive a value of .5. For a 'low' search it is the inverse. That is, if the boat with the lowest capsize ratio has 1.3, a boat with a capsize ratio of 3.9 would receive a value of 0.33. Only boats within the specified length range and in the database chosen in Part 1 will be searched. You can also eliminate any type or types of boat from those searched by entering their names separated by commas in the first field below. For example, entering 'Herreshoff,Bolger' would eliminate any boat with either name in its name. The results (the top three boats, their scores and the average score for boats searched) are reported in the text area below.
Output Field:
Minimum Length: | Maximum Length:
Capsize Ratio Hull Speed SA/Disp Disp/LWL LWL/Beam Motion Comfort Pounds/Inch
Search Direction:

Part 5, Propeller Sizing:

The material here is taken from an article by Dave Gerr NA in Sail Magazine (February 2001. pp. 81-84) entitled Sailing Screws. To really understand the numbers calculated below you should consult this article or his book Propeller Handbook. A note on the Maximum Sailing Speed calculated below:

This is also from Gerr's work. He has determined that the classic formula for Hull Speed ( 1.34 Sqrt(LWL) ) does not always apply, the 1.34 is not a constant, leading to, in some cases, much higher speeds. However, Gerr observes:

"For instance, a boat with a DL or 80 might have a SL multiplier of 2.11, but it couldn't achieve that speed under sail unless it had not just sufficient sail area, but the stability to stand up to such a sail area in the wind strengths needed to deliver the required power. Not an easy task!"

To use this form, select a boat, enter a Horsepower and Prop Type.
Boat Name
Horsepower (bhp)
Prop Type
Press to see results displayed below
Classic Hull Speed
Gerr's Maximum Speed Under Sail (SL)
Gerr's Maximum Speed Under Motor
Optimum Prop Diameter
New RPM