Calculate distance between two points in google maps V3

There actually seems to be a method in GMap3. It's a static method of the google.maps.geometry.spherical namespace.

It takes as arguments two LatLng objects and will utilize a default Earth radius of 6378137 meters, although the default radius can be overridden with a custom value if necessary.

Make sure you include:

<script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=false&v=3&libraries=geometry"></script>

in your head section.

The call will be:

google.maps.geometry.spherical.computeDistanceBetween (latLngA, latLngB);

It's Quite easy using Google Distance Matrix service

First step is to activate Distance Matrix service from google API console. it returns distances between a set of locations. And apply this simple function

function initMap() {
        var bounds = new google.maps.LatLngBounds;
        var markersArray = [];

        var origin1 = {lat:23.0203, lng: 72.5562};
        //var origin2 = 'Ahmedabad, India';
        var destinationA = {lat:23.0436503, lng: 72.55008939999993};
        //var destinationB = {lat: 23.2156, lng: 72.6369};

        var destinationIcon = 'https://chart.googleapis.com/chart?' +
            'chst=d_map_pin_letter&chld=D|FF0000|000000';
        var originIcon = 'https://chart.googleapis.com/chart?' +
            'chst=d_map_pin_letter&chld=O|FFFF00|000000';
        var map = new google.maps.Map(document.getElementById('map'), {
          center: {lat: 55.53, lng: 9.4},
          zoom: 10
        });
        var geocoder = new google.maps.Geocoder;

        var service = new google.maps.DistanceMatrixService;
        service.getDistanceMatrix({
          origins: [origin1],
          destinations: [destinationA],
          travelMode: 'DRIVING',
          unitSystem: google.maps.UnitSystem.METRIC,
          avoidHighways: false,
          avoidTolls: false
        }, function(response, status) {
          if (status !== 'OK') {
            alert('Error was: ' + status);
          } else {
            var originList = response.originAddresses;
            var destinationList = response.destinationAddresses;
            var outputDiv = document.getElementById('output');
            outputDiv.innerHTML = '';
            deleteMarkers(markersArray);

            var showGeocodedAddressOnMap = function(asDestination) {
              var icon = asDestination ? destinationIcon : originIcon;
              return function(results, status) {
                if (status === 'OK') {
                  map.fitBounds(bounds.extend(results[0].geometry.location));
                  markersArray.push(new google.maps.Marker({
                    map: map,
                    position: results[0].geometry.location,
                    icon: icon
                  }));
                } else {
                  alert('Geocode was not successful due to: ' + status);
                }
              };
            };

            for (var i = 0; i < originList.length; i++) {
              var results = response.rows[i].elements;
              geocoder.geocode({'address': originList[i]},
                  showGeocodedAddressOnMap(false));
              for (var j = 0; j < results.length; j++) {
                geocoder.geocode({'address': destinationList[j]},
                    showGeocodedAddressOnMap(true));
                //outputDiv.innerHTML += originList[i] + ' to ' + destinationList[j] + ': ' + results[j].distance.text + ' in ' +                    results[j].duration.text + '<br>';
                outputDiv.innerHTML += results[j].distance.text + '<br>';
              }
            }

          }
        });
      }

Where origin1 is your location and destinationA is destindation location.you can add above two or more data.

Rad Full Documentation with an example

  /**
   * Calculates the haversine distance between point A, and B.
   * @param {number[]} latlngA [lat, lng] point A
   * @param {number[]} latlngB [lat, lng] point B
   * @param {boolean} isMiles If we are using miles, else km.
   */
  function haversineDistance(latlngA, latlngB, isMiles) {
    const squared = x => x * x;
    const toRad = x => (x * Math.PI) / 180;
    const R = 6371; // Earth’s mean radius in km

    const dLat = toRad(latlngB[0] - latlngA[0]);
    const dLon = toRad(latlngB[1] - latlngA[1]);

    const dLatSin = squared(Math.sin(dLat / 2));
    const dLonSin = squared(Math.sin(dLon / 2));

    const a = dLatSin +
              (Math.cos(toRad(latlngA[0])) * Math.cos(toRad(latlngB[0])) * dLonSin);
    const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    let distance = R * c;

    if (isMiles) distance /= 1.609344;

    return distance;
  }

I found a version online which is 80% right but plugged in the wrong parameter and is inconsistent in using the inputs, this version fixed that completely

First, are you referring to distance as in length of the entire path or you want to know only the displacement (straight line distance)? I see no one is pointing the difference between distance and displacement here. For distance calculate each route point given by JSON/XML data, as for displacement there is a built-in solution using Spherical class

//calculates distance between two points in km's
function calcDistance(p1, p2) {
  return (google.maps.geometry.spherical.computeDistanceBetween(p1, p2) / 1000).toFixed(2);
}