Visible Range of Light

Calculate how far away you can actually see a navigational light.

Heights

Height of Light (ft)

Listed in chart notation or Light List — e.g. "180 ft"

Height of Eye (ft)

Your height above the water surface

Ranges

Nominal Range (nm)

Maximum range in clear weather — shown on chart or Light List (e.g. "18M")

Current Visibility (nm)

From weather report or NOAA radio — 10+ NM is clear, under 5 NM is haze/fog

Visible Range

--NM

Geographic Range--

Luminous Range--

Limiting factor--

Geographic range formula: d = 1.17 × √h (ft). Luminous range formula: RL = (visibility ÷ 10 × nominal range) + 1. Visible range = MIN(geographic, luminous).