leaflet_meters2pixels.js

        var m2px = 1;
        function newM2px() {
            var centerLatLng = map.getCenter();
            var pointC = map.latLngToContainerPoint(centerLatLng);
            var pointX = [pointC.x + 100, pointC.y];

            var latLngC = map.containerPointToLatLng(pointC);
            var latLngX = map.containerPointToLatLng(pointX);

            var distanceX = latLngC.distanceTo(latLngX)/100;

            reciprocal = 1 / distanceX;
            m2px = reciprocal;
        }
        function geoStyle(m) {
            return Math.ceil(m * m2px);
        }

        map.on("zoomend", function(){
            newM2px();
        }