Waterplane Area (AWP)

Compute the waterplane area at a given draft using coefficients or numerical integration of station breadths.

Result — Direct Method

AWP = — m²

Enter inputs to compute.
Odd number preferred for Simpson’s rule.
Values must correspond to equally spaced stations along LWL.
Result — Simpson Integration

AWP = — m²

Enter inputs to compute.

What is the Waterplane Area (AWP)?

The waterplane area (AWP) is the horizontal area of the ship’s hull at a specific draft. It represents the intersection of the hull geometry with the free surface and is a fundamental hydrostatic property.

Definition

AWP can be expressed using the waterplane coefficient:

AWP = CWP × LWL × BWL

where CWP is dimensionless, LWL is the waterline length, and BWL is the beam at the same waterline.

Engineering significance

Waterplane area directly affects tons per centimeter immersion (TPC), trim sensitivity, and initial transverse stability. Larger AWP values result in higher TPC and reduced sensitivity to small weight changes.

Draft dependency

AWP is always draft-specific. All inputs must correspond to the same waterline, especially when comparing values across loading conditions.

Numerical integration

When offsets or station breadths are available, waterplane area can be computed more accurately using Simpson’s rule. This method captures non-rectangular planform shapes that are not reflected by a single coefficient.

Related calculators

Tip: Always use LWL, BWL, and CWP values corresponding to the same draft.