Use this sailing calculation as a planning or educational cross-check for navigation, wind and current, rig loads, stability, anchoring, tides, visibility, performance, or recovery under explicitly stated conditions.

Dew point (°C)

Dew point temperature in degrees Celsius.

Air temperature (°C)

Dry bulb air temperature in degrees Celsius.

Assess fog risk from the temperature dew point spread; a spread of two degrees Celsius or less indicates conditions favourable for fog formation. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Fog risk

True when the spread is small enough for fog to form.

Spread (°C)

Temperature minus dew point in degrees Celsius.

• Actual conditions change with vessel design and loading, sea state, wind, current, tide datum, weather, chart accuracy, equipment, crew, regulations, and safety margins. Simplified formulas do not replace seamanship, approved stability data, or current navigation information.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Cross-check official charts, tide and weather services, instrument data, vessel manuals, and collision regulations; maintain conservative margins and a safe alternative plan.

• Anderson Turn Course

  Calculate the return course reached by an Anderson turn, which rotates the heading two hundred forty degrees toward the chosen turn direction to bring the vessel back along its original track.

• Capsize Screening Factor Calculator

  Compute the capsize screening factor; below two indicates better resistance to capsize.

• Position Error Circle

  Estimate the radius of the position error circle from a compass steering error as distance run times the error in degrees divided by fifty seven point three.