Use this sailing calculation for planning or education when the vessel, units, reference directions, environmental conditions, and assumptions are explicitly known.

Wind speed (kt)

Required number in kt. True wind speed driving the polar.

The cited overview of Sailing supplies background for the terminology and domain context used by this tool.^[1]

Guide the upwind heel angle as eight tenths of the wind speed in degrees, clamped between five and thirty degrees. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Target heel (deg)

Returned number in deg. Recommended upwind heel angle in degrees.

• Vessel design and loading, sea state, wind, current, tide datum, weather, chart accuracy, equipment, crew, and safety margins can make real conditions differ from a simplified result.
• Wind speed must be at least 0.
• Use finite inputs in the displayed units, preserve source measurements and assumptions, and independently verify consequential decisions.

Cross-check current charts, tide and weather services, instrument data, vessel manuals, and applicable navigation rules, and retain a conservative alternative plan.

• Downwind AWA Guide

  Guide the downwind target apparent wind angle as one hundred fifty degrees plus three tenths of the wind speed, clamped between one hundred thirty five and one hundred seventy degrees.

• Upwind TWA Guide

  Guide the upwind target true wind angle as forty five degrees minus half the wind speed, clamped between thirty and fifty five degrees.

• Upwind VMG Calculator

  Compute upwind velocity made good as target boat speed times the cosine of the true wind angle.