True Wind Speed & Angle (TWS / TWA) Vector Calculator
Calculate True Wind Speed (TWS in Knots), True Wind Angle (TWA relative to bow), True Wind Direction (TWD in degrees magnetic/true), and Velocity Made Good (VMG) from Apparent Wind and Boat Speed.
Apparent Wind & Boat Vector
Knots
Masthead anemometer readout.
deg
0° = Dead ahead, 90° = Beam, 180° = Astern.
Knots
°M
True Wind Vector Solution
CLOSE-HAULED BEATING
True Wind Speed (TWS)
13.0 Knots
Force 4 (Moderate Breeze)
True Wind Angle (TWA)
49.1°
Off Starboard Bow
True Wind Direction (TWD)
094.1°
Direction wind blows FROM
Velocity Made Good (VMG)
4.71 Knots
Upwind climb component
Tactical Sailing & Tacking Geometry
Apparent Wind Lift / Compression:
+5.5 Knots induced by boat motion
Opposite Tack Heading:
143.2° (after 98.2° tack)
Downwind VMG Component:
-4.71 Knots
Bowditch Marine Vector Navigation
Naval Science
Law of Cosines: TWS = sqrt[AWS² + BSP² - 2(AWS)(BSP)cos(AWA)]. TWA = arccos[(AWS·cos(AWA) - BSP) / TWS]. Upwind sailing compresses the apparent wind forward and increases wind speed over the deck, while running downwind reduces apparent wind velocity.