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.

Charted drying height (m)

Height of the drying patch above chart datum as printed on the chart.

Height of tide (m)

Height of tide above chart datum.

Compute the water depth over a charted drying patch by subtracting its drying height from the height of tide; a negative result means the patch remains exposed. 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]

Water depth (m)

Water over the patch; negative values mean the patch still dries by that amount.

• 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.

• Corrected Depth Calculator

  Add the height of tide to the charted depth sounding to obtain the actual depth of water.

• Berth Depth Check

  Check whether a marina berth holds enough water by adding the height of tide to the charted berth depth and comparing against the vessel draft.

• Bridge Clearance Calculator

  Compute the vertical margin under a chart-datum bridge clearance by subtracting both height of tide and vessel air draft.