Sea Distance Calculator
How to Use This Sea Distance Calculator
This free sea distance calculator helps you find nautical miles between any ports worldwide. Navigate the interactive map to plan your voyage with accurate measurements.
Select Your Starting Point
Click anywhere on the map or search for your departure port
Add Your Destination
Click the arrival location — it automatically calculates the route
View the Result
See total in nmi, kilometers, and statute mi instantly
Smart Routing: This calculator automatically plans routes through major sea passages like Panama Canal, Suez Canal, and Strait of Gibraltar.
Key Features
Interactive Map
Click anywhere or search 700+ major harbors worldwide
Smart Routing
Automatic navigation through canals and straits for accurate maritime paths
Multiple Stops
Create complex voyages with several locations — drag markers to adjust
Three Unit Options
View results in nmi, statute mi, or kilometers
Popular Sea Routes
Here are some common port to port distances:
| Route | NMI | MI | Via |
|---|---|---|---|
| Miami → Barcelona | 4,350 | 5,007 | Strait of Gibraltar |
| New York → Southampton | 3,180 | 3,660 | Direct Atlantic |
| Los Angeles → Tokyo | 4,840 | 5,571 | Pacific Ocean |
| Singapore → Dubai | 3,370 | 3,879 | Strait of Malacca |
Why Calculate Sea Distance?
Whether you’re preparing a boating trip, estimating fuel costs, or calculating transit time for your ship, precise information is essential. This tool provides:
- Accurate calculations — sailing distance based on actual maritime paths, not straight lines
- Multi-stop voyages — add locations for your complete journey
- Free online access — no registration required
- Professional data — coordinates displayed for each marker
Understanding NMI
A nautical mile (nmi) is the standard unit for measuring sea distance. It’s based on the Earth’s circumference:
1 nmi = 1.852 km = 1.151 statute mi
Mariners use this unit because it corresponds directly to degrees of latitude — making navigation simpler.
Frequently Asked Questions
How accurate is this calculator?
We use the Haversine formula for great-circle calculations and include smart routing through major maritime passages. Very accurate for trip estimation.
Can I measure between any two locations?
Yes! Click anywhere on the map to set custom spots, or try the port search. You can add multiple stops around the world.
Does it account for canals and straits?
Yes. With Smart Routing enabled, stops are automatically added through Panama Canal, Suez Canal, Gibraltar, and Malacca when needed.
How do I calculate voyage time?
Divide the total nmi by your vessel speed in knots. For example, 500 nmi at 10 knots = 50 hours of sailing.
This calculator provides estimates for reference. Always verify with official charts for actual navigation.