Boat Neck Calculation

REF: EN-204-DRAFTING

Use this tool to calculate the exact cut width and approximate circumference for a boat neckline (bateau neck). By inputting your shoulder width, desired strap thickness, and drop depth, this calculator utilizes elliptical geometry to output the precise measurements needed to draft a perfectly balanced horizontal neckline.

Boat Neck Calculation Formula

A boat neck (or bateau neckline) is characterized by a wide, horizontal opening that passes just below the collarbones and ends near the shoulder points. Because it spans horizontally rather than plunging vertically, calculating the exact fabric cut requires treating the opening as two joined semi-ellipses.

The Math Behind the Cut:

• Cut Width Calculation: To ensure the garment doesn't fall off the shoulders, you must preserve a fabric strap on each side. The formula is:
  Cut Width = Total Shoulder Width - (2 × Strap Width)
• Circumference (Perimeter) Calculation: The neckline is calculated as two distinct curves sharing the same width (major axis) but with different depth drops (minor axes for the front and back). Our system uses Ramanujan's approximation for the perimeter of an ellipse to accurately determine the length of edge binding or facing required.
• Front vs. Back Drop: The front drop is typically 1 to 2 inches deeper than the back drop to comfortably clear the trachea while maintaining the signature high-back aesthetic of the bateau style.