Calculate the width of one degree in meters at a given latitude on Earth

width-of-degree.js

const EARTH_CIR_METERS = 40075016.686;

function toRadians(degrees) {
  return degrees * Math.PI / 180;
};

function degreeWidth(lat){
  return EARTH_CIR_METERS / 360 * Math.cos(toRadians(lat));
}

//example 
const atEquator = degreeWidth(0); // 111319.490 meters
const atDenver = degreeWidth(39.73); // 85611.923 meters
const atChicago = degreeWidth(41.88); // 82882.3277 meters
const atNorthPole = degreeWidth(90); // ~0 m