Pathsphere

Two points · one chosen sphere

The distance along a sphere.

Enter two latitude/longitude pairs and a radius. Pathsphere calculates their central angle and the corresponding shorter surface distance, entirely in your browser.

A mathematical spherical model. No map, location permission or travel-route lookup.

Choose your points

Point A · decimal degrees
Point B · decimal degrees

Latitude −90 to 90; longitude −180 to 180. Plain decimals with up to 9 fractional places. Use minus for south/west; no degree symbols or hemisphere letters.

Above 0 to 1,000,000,000 km, up to 6 fractional places. The initial 6371 km is an illustrative chosen sphere, not a promise of Earth accuracy.

Keep the current calculation

Editing any field clears these outputs until you calculate again. Downloads are created locally; JSON retains the full finite numerical approximations.

Angle first

The angle at the sphere’s centre determines the fraction of a great circle between the points. Coordinates describe positions on that sphere.

Your radius

Multiplying the angle in radians by your radius gives kilometres. Double the radius and the distance doubles; the angle stays the same.

Model limits

Actual Earth routes, terrain and ellipsoidal differences are outside this tool. Read the method before interpreting the result.