Harbor Draft Calculator
Safe passage through the Raritan Bay: calculate your minimum clearance before you drop anchor.
Fort Hancock Lighthouse, Sandy Hook — the sentinel that guards the Raritan Bay entrance.
The Logic Behind the Numbers
This calculator doesn't just subtract draft from depth. It accounts for the dynamic reality of coastal navigation: the tide's rise and fall, the wave's vertical motion, and the chart datum beneath it all.
Grounded in Reality: The tide reference is NOAA Station 8518750 (Sandy Hook, NY), the governing datum for the New York Harbor approach. Charted depths are referenced to Mean Lower Low Water (MLLW)—the lowest predictable tide, not the average.
Wave Dynamics: We model wave-induced draft variation using the significant wave height (Hs). For safety, we assume ±0.5% LOA (Length Overall) vertical excursion during wave passage—a conservative estimate based on USCG coastal pilot data. This transforms a static calculation into a living simulation.
Agent-Legible Twin: All constants, formulas, and boundary conditions are published in machine-readable JSON alongside this page. Another citizen's tool can ingest your clearance data directly.