How to Calculate Sail Area

Larger sails equates to more sailing power.

Sail area directly affects how much power your sailboat will have. The bigger the sail area, the more wind your sail will be able to catch and the faster your boat will go. The bad news is that you will have to use math to calculate sail area. On the bright side, all you need are two simple geometry equations. The equation you use will depend on the shape of the sail.

Things You'll Need

• Calculator
• Sail measurements or tape measure

Instructions

Calculating Sail Area for Square or Rectangular Sales

1. Find the height and width of your sail. You can either find these specifications with the information that came with your boat or you can physically measure the sails yourself.

2. Enter the measurements into the following equation: height x width = sail area. For example, if your sail's measurements are 4 feet by 5 feet, the equation should look as follows: 4 feet x 5 feet = sail area.

3. Calculate this equation for each of your sails and add them together. This will give you your sail area in square footage, square inches or any unit of measurement you used. In the previous example, the sail area would be 20 square feet.

Calculating Sail Area for Triangular Sails

1. Measure the base of the sail and the height of the sale with a tape measure or find these specifications in the boat's manual.

2. Enter the measurements into the following equation: 1/2 x base x height = sail area. For example, if your sail has a base of 4 feet and a height of 5 feet, your equation will look as follows: 1/2 x 4 feet x 5 feet = sail area.

3. Calculate the sail area for each sail and add them together to get your boat's total sail area. In the previous example, the sail area for would be 10 square feet.

Tips & Warnings

• One common sail shape that is neither square, rectangular or triangular is the four-sided sail. This sail shape does not lend itself to easy calculation, so you'll need to make it fit one of our equations. Split the sail into two triangles by drawing an imaginary diagonal line that splits the sail in half. Then calculate the sail area for the two triangles created by the imaginary line using the triangular sail area equation (1/2 x base x height = sail area). Add the two calculations together to get your sail area for your four-sided sail.

References

• Pipe Line: Sail Area Calculator
• Boat Building Links: Sail Area Math