Understand why flight distance and driving distance are different, with real-world examples and practical advice for travel planning.
Flight distance follows the great-circle path between two airports. Driving distance follows real roads, which add detours, mountains, and water crossings. The two numbers can differ by 30% on land routes — and by thousands of kilometers across water.
This guide explains why, with real examples like London–New York (impossible to drive) and Los Angeles–San Francisco (driving and flying nearly identical).
By the end you will know which number to use for which planning question.
Every distance on SnapDistance is computed with the Haversine formula, which measures the great-circle distance between two points on a sphere. The formula uses the latitude and longitude of each city — sourced from OpenStreetMap and Photon — and returns the shortest path along the Earth's surface. This is the same technique used by aviation route planners, maritime navigators, and most modern mapping APIs.
Results are returned in kilometres, miles, and nautical miles. SnapDistance also estimates flight time using a representative cruise speed of approximately 900 km/h plus 30 minutes of taxi, takeoff, and landing overhead. Driving time is approximated by multiplying the great-circle distance by 1.3 (a typical road-network detour factor) and dividing by an average highway speed. These estimates are designed for planning, not for operational navigation.
Because all calculations run client-side in your browser, no city pair you enter is ever sent to a SnapDistance server. The only network requests made by the calculator are to the Photon geocoding API for autocomplete, and (with your consent) to Google Analytics for anonymous usage statistics.
Straight-line distance is the shortest possible separation between two locations. It is the same number you would draw with a ruler on a globe, ignoring roads, oceans, mountains, and political borders. For comparing two cities, two airports, or two coordinates, it is the most consistent and source-of-truth figure.
Real-world routing — the path a car, train, ship, or commercial flight actually follows — is almost always longer. Roads detour around terrain, flights follow air-traffic-control corridors and jet-stream-friendly tracks, and trains follow fixed rights-of-way. As a rule of thumb, driving routes are 1.2–1.5× the straight-line distance, and commercial flights are 1.02–1.10× the great-circle distance for routes longer than 1,000 km.
Knowing both numbers helps you frame a trip correctly: use straight-line distance to compare options at a glance, then switch to a routing service like Google Maps or a flight-search engine when you need exact times.
The fastest way to apply what this guide covers is to open the SnapDistance calculator and try a route you actually care about — a commute, a planned trip, or a city pair you have always been curious about. The number you get back is the same straight-line figure professional planners start from when scoping a journey.
Combine the calculator with the related city-hub and country pages on SnapDistance to see how a single route fits into a larger network. Hub pages list dozens of distances from one origin city, and country pages aggregate routes within a single nation, which together make it easy to compare alternatives without re-typing every search.
If you want to go further, the other guides in the SnapDistance library cover specific subtopics in depth — including the Haversine formula derivation, kilometres vs miles conversion, flight-time vs distance, driving-distance multipliers, and realistic one-day driving limits.
Distances are computed with the Haversine formula and city coordinates from OpenStreetMap, so the great-circle figure is accurate to within a few hundred metres for almost any city pair. Flight and driving time estimates are deliberate approximations — flight time uses a representative cruise speed and adds taxi/takeoff overhead, and driving time multiplies straight-line distance by 1.3 to approximate real road routing. Always confirm with a routing service before booking.
Great-circle distance is the shortest path between two points along the surface of the Earth, treating the planet as a sphere. Driving distance follows actual roads, which add detours around terrain, water, and political borders. On most continents, the driving distance is roughly 1.2–1.5× the great-circle distance.
Yes. The calculator, every city-hub page, every country page, the comparison tool, and all guides are free and require no account. There are no usage limits, no paywalls, and no ads.
No. All distance calculations run inside your browser, so the city pairs you enter are never sent to a SnapDistance server. The only data the site can see is anonymous Google Analytics traffic, and only if you accept the analytics cookie when you first visit.
Yes. SnapDistance is a Progressive Web App. Once you have visited the site, you can add it to your home screen on iOS or Android, or install it as a desktop app on Chrome and Edge. The cached pages and the calculator continue to work without an internet connection.