A sail plan is a drawing of a sailing craft, viewed from the side, depicting its sails, the spars that carry them and some of the rigging that supports the rig.  By extension, "sail plan" describes the arrangement of sails on a craft.   A sailing craft may be waterborne (a ship or boat), an iceboat, or a sail-powered land vehicle.
Depending on the level of detail, a sail plan can be a visual inventory of the suit of sails that a sailing craft has, or it may be part of a construction drawing. The sail plan may provide the basis for calculating the center of effort on a sailing craft, necessary to compare with the center of resistance from the hull in the water or the wheels or runners on hard surfaces. Such a calculation involves the area of each sail and its geometric center, referenced from a specific point. 
Considerations for a sail inventory in a yacht include the type of sailing (cruising, racing, passage-making, etc.) and the weather conditions anticipated. An assessment starts with a sail plan that depicts each kind of sail under consideration. The sail plan becomes a guide for which sails to use under the anticipated weather conditions, while under way. Sail names encompass fore-and-aft rigs, square rigs, and rigs that encompass both types.
A cutter-rigged yacht, intended for off-shore sailing might have a sail inventory that includes: a mainsail, a roller furling genoa, and a working staysail for most wind conditions, and, for strong winds, a storm staysail and trysail. Sails for lighter winds would include a spinnaker, a drifter, and a mainsail with lighter sail cloth. 
Each sail has a separate set of considerations within the plan, for example with a performance sloop one may consider the following about its suit of sails: 
A square-rigged sailing vessel carries both fore-and-aft sails, the jibs, staysails and mizzen sail, and square sails. Their naming conventions are: 
In the late 19th and early 20th centuries, choosing a sail plan for a displacement watercraft stemmed from the size and tonnage of the vessel, its purpose (working vessel, cargo vessel or yacht) and the anticipated winds in the region where it was expected to sail. In that period, sail plans might start from smallest to largest boat or ship in a hierarchy of sailing rigs:  
Working boats and coastal freighters
Ocean-going merchant vessels
The following sail plans are at various scales.
A sloop is a sailboat with a single mast typically having only one headsail in front of the mast and one mainsail aft of (behind) the mast. Such an arrangement is called a fore-and-aft rig, and can be rigged as a Bermuda rig with triangular sails fore and aft, or as a gaff-rig with triangular foresail(s) and a gaff rigged mainsail.
A schooner is a type of sailing vessel defined by its rig: fore-and-aft rigged on all of two or more masts and, in the case of a two-masted schooner, the foremast generally being shorter than the mainmast. A common variant, the topsail schooner also has a square topsail on the foremast, to which may be added a topgallant. Differing definitions leave uncertain whether the addition of a fore course would make such a vessel a brigantine. Many schooners are gaff-rigged, but other examples include Bermuda rig and the staysail schooner.
A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture.
Sailing rigs describe the arrangement of sailing vessels' rig components, including their spars, rigging, and sails. Examples include a schooner rig, cutter rig, junk rig, etc. Rigs may be broadly categorized as fore-and-aft and square-rigged. They may incorporate a mixture of both categories. Within the fore-and-aft category there is a variety of triangular and quadrilateral sail shapes. Spars or battens may be used to help shape a given kind of sail. Each rig may be described with a sail plan—formally, a drawing of a vessel, viewed from the side.
A brigantine is a two-masted sailing vessel with a fully square-rigged foremast and at least two sails on the main mast: a square topsail and a gaff sail mainsail. The main mast is the second and taller of the two masts.
A brig is a type of sailing vessel defined by its rig: two masts which are both square-rigged. Brigs originated in the second half of the 18th century and were a common type of smaller merchant vessel or warship from then until the latter part of the 19th century. In commercial use, they were gradually replaced by fore-and-aft rigged vessels such as schooners, as owners sought to reduce crew costs by having rigs that could be handled by fewer men. In Royal Navy use, brigs were retained for training use when the battle fleets consisted almost entirely of iron-hulled steamships.
A jib is a triangular sail that sets ahead of the foremast of a sailing vessel. Its tack is fixed to the bowsprit, to the bows, or to the deck between the bowsprit and the foremost mast. Jibs and spinnakers are the two main types of headsails on a modern boat.
A topsail ("tops'l") is a sail set above another sail; on square-rigged vessels further sails may be set above topsails.
A staysail ("stays'l") is a fore-and-aft rigged sail whose luff can be affixed to a stay running forward from a mast to the deck, the bowsprit, or to another mast.
A cutter is a name for various types of watercraft. It can apply to the rig of a sailing vessel, to a governmental enforcement agency vessel, to a type of ship's boat which can be used under sail or oars, or, historically, to a type of fast-sailing vessel introduced in the 18th century, some of which were used as small warships.
Gaff rig is a sailing rig in which the sail is four-cornered, fore-and-aft rigged, controlled at its peak and, usually, its entire head by a spar (pole) called the gaff. Because of the size and shape of the sail, a gaff rig will have running backstays rather than permanent backstays.
The mast of a sailing vessel is a tall spar, or arrangement of spars, erected more or less vertically on the centre-line of a ship or boat. Its purposes include carrying sails, spars, and derricks, giving necessary height to a navigation light, look-out position, signal yard, control position, radio aerial or signal lamp. Large ships have several masts, with the size and configuration depending on the style of ship. Nearly all sailing masts are guyed.
A Bermuda rig, Bermudian rig, or Marconi rig is a configuration of mast and rigging for a type of sailboat and is the typical configuration for most modern sailboats. This configuration was developed in Bermuda in the 1600s; the term Marconi, a reference to the inventor of the radio, Guglielmo Marconi, became associated with this configuration in the early 1900s because the wires that stabilize the mast of a Bermuda rig reminded observers of the wires on early radio masts.
A full-rigged ship or fully rigged ship is a sailing vessel's sail plan with three or more masts, all of them square-rigged. A full-rigged ship is said to have a ship rig or be ship-rigged. Such vessels also have each mast stepped in three segments: lower mast, top mast, and topgallant mast. Other large, multi-masted sailing vessels may be regarded as ships while lacking one of the elements of a full-rigged ship, e.g. having one or more masts support only a fore-and-aft sail or having a mast that only has two segments.
Earl of Pembroke is a wooden, three-masted barque, currently used for maritime festivals, charters, charity fund raising, corporate entertaining and film work.
The masts of traditional sailing ships were not single spars, but were constructed of separate sections or masts, each with its own rigging. The topmast is one of these.
A foresail is one of a few different types of sail set on the foremost mast (foremast) of a sailing vessel:
KRI Dewaruci is a Class A tall ship and the only barquentine owned and operated by the Indonesian Navy. She is used as a sail training vessel for naval cadets and is the largest tall ship in the Indonesian fleet. Dewaruci also serves as a goodwill ambassador for Indonesia to the rest of the world.
A jackass-barque, sometimes spelled jackass bark, is a sailing ship with three masts, of which the foremast is square-rigged and the main is partially square-rigged and partially fore-and-aft rigged (course). The mizzen mast is fore-and-aft rigged.
The following outline is provided as an overview of and topical guide to sailing: