Mileage Calculator

Straight-line distance versus driving distance

This calculator reports the straight-line distance between two city centers: the length of the most direct possible line connecting them, ignoring roads, terrain, and everything else in between. A real driving distance is almost always longer, since roads curve around lakes, mountains, other towns, and each other rather than cutting a straight path. The gap between the two numbers is usually somewhere between 10% and 40% depending on the terrain and road layout between the two places, sometimes more in mountainous or coastal areas where roads have to wind considerably.

Worked example. New York and Boston sit close enough, and with a reasonably direct interstate connecting them, that straight-line and driving distance land in the same rough neighborhood: this calculator's straight-line figure comes out under 200 miles, while the real driving route along I-95 is closer to 215 miles. For a pair of cities separated by a mountain range or a large body of water, the gap is usually much larger, since the straight line cuts through the obstacle while any real road has to go around it.

The table pairs this calculator's straight-line figure for seven city pairs with the approximate road distance between the same cities on the most direct interstate route. The road figures are rounded to the nearest five miles and shift by a few miles between mapping services, depending on where in each city the route starts and ends.

The road adds only about 10 percent between New York and Washington, the smallest gap in the table, and about 40 percent between Denver and Salt Lake City, the largest, where the highways detour around the mountains. The seven ratios average about 1.19, so multiplying a straight-line figure by 1.2 makes a fair first guess at a typical road distance. It is only a first guess, because a bay or a mountain range between two cities can push a route well outside that range.

How the straight-line distance is calculated

The distance between two points on a sphere, which the Earth approximately is, is calculated with the haversine formula, using each city's latitude and longitude:

The formula accounts for the Earth's curvature, so it stays accurate for city pairs on opposite sides of the globe, not just nearby ones. This calculator runs it directly in your browser using each city's bundled coordinates; nothing is looked up from an external service.

Worked example, New York to Los Angeles. The calculator holds 40.7143 N, 74.0060 W for New York and 34.0522 N, 118.2437 W for Los Angeles. With the angles converted to radians for the sine and cosine steps, the formula works out as follows.

Straight-line distances between major U.S. cities

If you only need a common pair, the chart below saves running the calculator. It lists the straight-line miles from ten U.S. cities to five well-known destinations, rounded to the nearest mile. Every number comes from the function the calculator itself runs, with the same coordinates, so the chart and the tool always agree, and a dash marks a city measured against itself.

Find the starting city in the left column and the destination across the top. Distances read the same in both directions, so Chicago to Los Angeles is the same 1,741 miles as Los Angeles to Chicago. For any pair that is not in the chart, type the two names into the calculator above.

When straight-line distance is the number you want

Straight-line distance answers a different question from the drive, and for some questions it is the better answer. Radio and cell coverage, delivery radius limits and any search for places within a set number of miles all work in a straight line, because a signal does not follow a road. Flights follow routes close to a great circle, so this also works as a rough airline distance calculator or air mileage calculator for two city centers. Airports sit outside the center, so the flight distance to or from an airport differs a little from the figure here.

The same measurement goes by several names. Distance as the crow flies, as the bird flies mileage, great-circle distance and airline distance all describe the shortest path over the Earth's surface between two points. That makes this an as-the-crow-flies distance calculator as much as a mileage calculator, and the distance the crow flies is never longer than any road or flight route between the same two places.

Why this mileage calculator does not offer real driving distance

A real driving distance and turn-by-turn driving time come from a routing engine, a service that has an actual digital map of every road, current speed limits, and often live traffic, and calculates the shortest or fastest real route between two points along that road network. Running that kind of service costs money per request and requires a paid API key from a provider like Google Maps, so rather than build a calculator that quietly breaks once a usage limit or a subscription lapses, this tool sticks to something it can compute entirely on its own, the straight-line distance, and states that limitation plainly instead of hiding it. For the real route, the result includes a direct link to Google Maps with both cities already filled in.

Reading the estimated driving time

The estimated driving time divides the straight-line distance by an assumed average speed to produce a rough number, not a real routing estimate. It does not know the actual roads, speed limits, traffic conditions, or how winding a real route is, so treat it as a loose planning figure, useful for a rough sense of scale (a two-hour trip versus a two-day trip), not a number to build a real travel schedule around. The Google Maps link in the result gives an actual driving-time estimate for the real route instead.

For a quick sense of scale, the table shows what the assumed 55 mph average gives for common distances. Real trips run longer once stops, traffic and slower roads at either end are added, and shorter on open highway with a higher speed limit. Use it to judge whether the trip from point A to point B is a matter of hours or of days, not to set a departure time. As a drive time calculator it is deliberately crude; the speed calculator solves for time, speed or distance when you know two of the three and want to try a different average speed.

How to find distance between two cities

1. Type the starting city in the From box and pick it from the suggestions.
2. Type the destination in the To box the same way.
3. Press Calculate to see the distance in miles and kilometers, with the estimated driving time underneath.
4. Open the Google Maps link in the result for the real route and its driving time, then press Clear to try another pair.

Entering a city correctly

Start typing a city name in either field and matching suggestions appear; picking one from the list guarantees it parses correctly. Typing by hand works too, as a plain city name (“Boston”) or, for a U.S. or Canadian city whose name exists in more than one state or province (“Portland” is both Oregon and Maine), the city followed by its state or province abbreviation (“Portland, OR” or “Portland OR”, either format works). A name the calculator does not recognize, or one that matches more than one place, is flagged directly rather than guessed at.

Which kind of mileage do you need?

People type “mileage” into a search box and mean several different things. This calculator answers the first row of the table; the others have a tool of their own or a one-line calculation.

Converting the result to other units

The result already shows both miles and kilometers, so no separate conversion step is needed either way. For a unit this calculator does not cover directly, such as nautical miles, the unit converter handles length conversions generally.