# Earth Radius by Latitude Calculator

Earth isn't a perfect sphere, but is oblate at its poles, due to its rotation. Therefore, the Earth radius isn't constant, but it can be calculated for every location. For this calculation, the longitude isn't needed. Mathematically, Earth is a spheroid.

Earth radius at sea level is 6378.137 km (3963.191 mi) at the equator. It is 6356.752 km (3949.903 mi) at the poles and 6371.001 km (3958.756 mi) on average. The height above sea level of the location is added. Please enter the latitude in decimal degrees, here you can convert coordinates.

## Formula for the calculation

latitude B, radius R, radius at equator r_{1}, radius at pole r_{2}

R = √ [ (r_{1}² * cos(B))² + (r_{2}² * sin(B))² ] / [ (r_{1} * cos(B))² + (r_{2} * sin(B))² ]

*Height above sea level* can be negative, then you are below sea level.