Maritime Calculators Index
Browse all maritime calculation tools including navigation, distance, speed, and sailing performance formulas.
Maritime Calculators
Free online tools for nautical and sailing calculations. Convert distances and speeds, plan passages, and reference wind and anchoring.
Popular calculators
Nautical Mile Converter
Convert between nautical miles, statute miles, kilometers, and meters. Essential for chart work and passage planning.
Use calculator →Knots to km/h Converter
Convert speed in knots to kilometers per hour. One knot equals 1.852 km/h.
Use calculator →Hull Speed Calculator
Estimate theoretical hull speed from waterline length using the classic 1.34 × √LWL rule for displacement hulls.
Use calculator →Initial Bearing Calculator
Compute the initial true bearing from one lat/lon waypoint to another (great-circle start heading).
Use calculator →Great Circle Distance Calculator
Compute the shortest distance between two locations on Earth using latitude and longitude. Results in nautical miles and kilometers.
Use calculator →Boat Fuel Consumption Calculator
Estimate fuel needed for a passage from consumption rate and travel time or distance and speed.
Use calculator →VMG Calculator
Velocity made good toward a mark: boat speed × cos(angle off bow to the mark).
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All maritime calculators
Knots Speed Converter
Convert speed between knots, miles per hour, kilometers per hour, and meters per second. Standard for marine and aviation speed.
Use calculator →Distance to Horizon Calculator
Find how far the horizon is from your height of eye. Uses the standard nautical formula for horizon distance.
Use calculator →Sailing Time Calculator
Estimate how long it will take to cover a given distance at a constant speed. Supports nautical miles, km, miles, knots, km/h, and mph.
Use calculator →Anchor Scope Calculator
Find how much anchor rode to pay out for a given water depth and scope ratio. Supports feet and meters.
Use calculator →Beaufort Scale Calculator
Enter wind speed in knots, mph, km/h, or m/s to get the corresponding Beaufort force and sea state description.
Use calculator →Apparent Wind Calculator
Compute apparent wind speed and angle from true wind speed, true wind angle (from the bow), and boat speed. All inputs in knots.
Use calculator →Wave Height Calculator
Estimate significant wave height from wind speed. Uses simplified empirical relationship for open water.
Use calculator →Fathom Converter
Convert between fathoms, feet, and meters. Fathoms are commonly used for water depth and anchor chain.
Use calculator →Wind Chill Calculator
Calculate apparent temperature (wind chill) from air temperature and wind speed. Useful for cold-weather sailing.
Use calculator →Rhumb Line Distance Calculator
Approximate rhumb-line distance in nautical miles between two positions (plane sailing at mean latitude).
Use calculator →Statute Miles to Nautical Miles Converter
Convert statute (land) miles to nautical miles using 1 nm = 1.15078 statute miles.
Use calculator →Celsius to Fahrenheit Converter
Convert air or water temperature between °C and °F for forecasts, logs, and crew briefings.
Use calculator →Feet to Meters Converter
Convert feet to meters (and vice versa) for dock lines, mast heights, and bridge clearances.
Use calculator →Latitude Degrees to Nautical Miles
Convert degrees of latitude (or longitude at the equator) to nautical miles along a meridian.
Use calculator →Fuel Range Calculator (Nautical Miles)
Estimate range in nautical miles from cruising speed, fuel aboard, and consumption rate.
Use calculator →Anchor Shackle to Feet Calculator
Convert anchor chain shackles (15 fathoms each) to total feet of rode.
Use calculator →Bar to PSI Converter
Convert pressure in bar to pounds per square inch for gauges and systems.
Use calculator →Liters to US Gallons Converter
Convert liters to US gallons for fuel tanks and water tanks.
Use calculator →Cables to Nautical Miles Converter
Convert cables (1/10 nm) to nautical miles for chart and pilotage notation.
Use calculator →Geographic Range of a Light Calculator
Estimate combined geographic visible range (nm) from height of eye and light elevation.
Use calculator →Radar Horizon Calculator
Approximate radar line-of-sight horizon in nautical miles from antenna height.
Use calculator →Current Drift Distance Calculator
Distance run by set in nautical miles: current speed × time in hours.
Use calculator →Sail Area to Displacement Ratio
Classic ratio SA ÷ DISPL^(2/3) with displacement in pounds (not long tons).
Use calculator →Capsize Screening Factor
Simple beam / (DISPL/64)^(1/3) style screening number (displacement in pounds).
Use calculator →Pounds to Kilograms Converter
Convert weight in pounds to kilograms for provisions, ground tackle, and cargo.
Use calculator →Kilowatts to Horsepower Converter
Convert engine power kW to mechanical horsepower for marine diesels and electric drives.
Use calculator →Meters per Second to Knots Converter
Convert m/s to knots for scientific wind data or current models.
Use calculator →Inches of Mercury to Millibar Converter
Convert inHg to hPa/mbar for barometers and weather maps.
Use calculator →Bilge Pump Time Calculator
Minutes to move a volume at a given pump rate (US gal, GPM).
Use calculator →Wavelength from Wave Period
Deep-water wavelength from period using L = gT²/(2π).
Use calculator →Longitude Minutes to Nautical Miles
Nautical miles per minute of longitude at a given latitude (cosine scaling).
Use calculator →True from Magnetic Heading
True heading = magnetic heading + easterly variation (subtract westerly).
Use calculator →Cross Track Error Calculator
Approximate XTE in nm from distance run along track and bearing error.
Use calculator →Speed Over Ground Calculator
Vector sum of speed through water and current using law of cosines.
Use calculator →Mercator Scale Factor Calculator
Chart scale exaggeration k = sec(φ) at a given latitude.
Use calculator →Feet of Rode to Shackles
Convert deployed rode length in feet to standard anchor shackles (90 ft each).
Use calculator →Square Feet to Square Meters Converter
Convert sail area or deck area between ft² and m².
Use calculator →Cubic Feet to Liters Converter
Tank volume conversion for bilge, water, or fuel compartments.
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