Halfway point between two places

Worked example: Springfield, IL and Nashville, TN

The capitals are 294.5 miles apart in a straight line, so each leg is 147.2 miles. The geodesic midpoint is 37.9822, -88.1817. These are the eight Census places of 1,000+ people closest to it:

How the midpoint is found

Averaging two latitudes and two longitudes gives the midpoint on a flat map, which is the wrong answer on a globe. Meridians draw together as they approach the poles, so the true halfway point of an east-west trip sits a little poleward of the simple average.

This tool converts both places to vectors on a unit sphere, adds them, and converts the sum back to latitude and longitude. The result lies on the great circle between the two places, at equal distance from each. Distances from it are measured with the haversine formula on a sphere of radius 6,371.0088 km.

How towns near the midpoint are chosen

The midpoint rarely falls inside a town. So the tool scans all 10,255Census places with a Vintage 2024 population of 1,000 or more, takes the eight closest to the midpoint, and measures each one back to both endpoints. The imbalance column is the difference between those two legs.

Sort by fairest split when the goal is equal travel. Sort by largest when you need a town big enough for a restaurant or a hotel. A town slightly off the midpoint can still be fair if it sits along the line between the two places, and a town right next to the midpoint can be unfair if it lies off to one side.

Limits

All legs are straight lines. A river, a mountain range, or a gap in the road network can make a town that is fair on the map unfair by car. Census-designated places are not included because the subcounty population estimates the site uses do not cover them, so some unincorporated communities are missing from the list.

To check the road trip, open the crow flies calculator with each leg and press the driving comparison. If the routing services are down, the site says so rather than guessing.

Picking a meeting town from the list

Start with the imbalance column. An imbalance of a few miles means both parties travel about the same straight-line distance. Then look at population if you need a place with services. The largest sort puts the bigger towns first.

Next, test the two legs by road. Open the crow flies calculator with the first place and your chosen town, run the driving comparison, then repeat with the second place. If one road leg is much longer than its straight line, a river crossing or a missing highway link is usually the cause, and the next town on the list may split the drive more fairly.

For three or more people, the midpoint of two is not enough. Measure each person's leg to a few candidate towns and pick the one that keeps the longest leg shortest.