Converting Meters into radians on the WGS84 Ellipsoid

Hello, I am developing an application in which a user can input a number (in meters) and the software draws a square with a side length of the user input. Currently, I am just using a cartesian3 as the Centerpoint and creating a rectangle from a cartesian array. However, I have noticed that it is a rectangle as it is not accounting for the curvature of the earth. Is there a way to convert meters into a radian or degree difference?