About

Maritime and aviation professionals rely on the Knot as the standard unit of speed, defined as one nautical mile per hour. While universal in navigation, converting these figures into land-based units like Kilometers per hour or Miles per hour is frequently required for logistical planning, port reporting, and cross-disciplinary communication. Accuracy is non-negotiable; a miscalculation in speed estimates can alter arrival times, fuel consumption projections, and safety margins.

This tool bridges the gap between nautical and terrestrial velocity. Beyond simple conversion, it integrates the Beaufort Wind Scale to provide environmental context, translating abstract speed numbers into observable sea conditions. Furthermore, the horizon calculator estimates the visual limit based on observer height, a critical factor for bridge watchkeeping and coastal navigation.

Formulas

The conversion between nautical and standard land speed units relies on the definition of the nautical mile (1852 meters).

Knots to km/h:
v_km/h ≈ 1.852 × v_kt

Knots to mph:
v_mph ≈ 1.15078 × v_kt

Distance to Horizon (Geometric):
d ≈ 3.57 × √h

Where d is distance in kilometers and h is the eye height in meters. Atmospheric refraction may increase visible distance by approximately 8%.

Reference Data

Beaufort Number	Description	Wind Speed (knots)	Sea State	Wave Height (m)
0	Calm	0 − 1	Sea like a mirror	0
1	Light Air	1 − 3	Ripples, no foam crests	0.1
2	Light Breeze	4 − 6	Small wavelets, glassy crests	0.2 − 0.3
3	Gentle Breeze	7 − 10	Large wavelets, crests break	0.6 − 1.0
4	Moderate Breeze	11 − 16	Small waves, frequent whitecaps	1.0 − 1.5
5	Fresh Breeze	17 − 21	Moderate waves, spray	2.0 − 2.5
6	Strong Breeze	22 − 27	Large waves, foam streaks	3.0 − 4.0
7	High Wind	28 − 33	Sea heaps up, white foam blown	4.0 − 5.5
8	Gale	34 − 40	Moderately high waves, spindrift	5.5 − 7.5
9	Strong Gale	41 − 47	High waves, dense streaks	7.0 − 10.0
10	Storm	48 − 55	Very high waves, sea white	9.0 − 12.5
11	Violent Storm	56 − 63	Exceptionally high waves	11.5 − 16.0
12	Hurricane	≥ 64	Air filled with foam, sea white	≥ 14.0

Frequently Asked Questions

A Knot is based on the nautical mile, which corresponds to one minute of latitude on the Earth's surface. This ties speed directly to map coordinates (degrees and minutes), making it essential for maritime and air navigation where geometry matters more than linear road distance.

The formula used is a geometric approximation. In reality, atmospheric refraction (bending of light) usually allows you to see slightly further than the geometric horizon. Weather conditions like fog or heat haze can significantly reduce this visibility.

Force 8 corresponds to a "Gale" on the Beaufort scale. It indicates wind speeds of 34-40 knots and sea conditions featuring moderately high waves with spindrift. It is a critical threshold for small vessel safety.

Yes. Aviation also uses Knots (True Airspeed and Indicated Airspeed). The conversion to km/h or mph is identical, although the Beaufort scale and Horizon calculations are relevant primarily to maritime surface operations.