Route, Bearing & ETA Calculator
Enter a starting point and destination to calculate great-circle distance, initial true bearing, magnetic heading, and travel time.
What this navigation calculator does
This navigation calculator gives you a quick planning view of a trip between two coordinates. It computes:
- Great-circle distance (the shortest path on Earth’s surface)
- Initial true bearing (the first heading from your start point)
- Magnetic heading estimate (after applying declination)
- Estimated travel time based on your average speed
It’s useful for sailors, pilots, hikers, and anyone building route planning tools. While it’s simple, it uses standard geospatial math and gives practical, fast estimates.
How the calculator works
1) Distance with the Haversine formula
The Earth is round-ish, not flat, so latitude/longitude distances need spherical geometry. The calculator uses the Haversine formula to estimate surface distance between two points. This produces a reliable result for everyday navigation tasks.
2) Initial bearing (true course)
The initial bearing is the direction you would start traveling from Point A toward Point B, measured clockwise from true north (0° to 360°). On long routes, your heading changes over time on a great-circle path, so this value is a starting direction rather than a constant heading.
3) Magnetic heading conversion
Many compasses reference magnetic north, not true north. If you provide declination (variation), the tool estimates magnetic heading using:
Magnetic Heading = True Bearing - Declination
Use positive values for east declination and negative values for west declination.
4) ETA (estimated time en route)
Given your average speed, the calculator estimates duration. It outputs total hours and a human-friendly breakdown in days, hours, and minutes.
When to use this tool
- Pre-trip route planning for marine navigation
- Quick flight leg estimation in general aviation planning
- Backcountry expedition distance and travel-time estimates
- Educational demonstrations of geodesy, bearings, and ETA logic
- Building a baseline before loading a route into dedicated nav software
Example scenario
Suppose you’re planning a route from Los Angeles to New York. After entering both coordinate pairs and speed, the calculator returns distance, initial bearing, and trip duration. If you include local declination, it also estimates the magnetic heading to compare against compass readings.
This makes it easy to sanity-check plans before moving to more advanced systems like chart plotters, EFB apps, or avionics.
Best practices for safer navigation
- Always cross-check with updated charts and official data.
- Account for wind, current, terrain, restricted areas, and weather.
- Use waypoint-based planning for long routes instead of one giant leg.
- Recalculate frequently when conditions or speed change.
- Treat estimated headings and times as planning values, not guarantees.
Limitations
This calculator is intentionally lightweight. It does not model fuel consumption, no-fly zones, tides, current drift, wind correction angle, terrain hazards, geoid anomalies, or turn-by-turn routing constraints. For operational decision-making, combine this output with professional tools and local guidance.
Final thoughts
A good navigation calculator helps you think clearly: where you’re going, how far it is, what heading you start with, and how long it might take. That simple structure dramatically improves planning quality. Use it to develop better route intuition, then layer in real-world constraints for execution.