diff --git a/core/constants.js b/core/constants.js
index 229ca0d4d..a786c173a 100644
--- a/core/constants.js
+++ b/core/constants.js
@@ -26,6 +26,17 @@
 
 goog.provide('Blockly.constants');
 
+/**
+ * The multiplier for scroll wheel deltas using the line delta mode.
+ * @type {number}
+ */
+Blockly.LINE_MODE_MULTIPLIER = 40;
+
+/**
+ * The multiplier for scroll wheel deltas using the page delta mode.
+ * @type {number}
+ */
+Blockly.PAGE_MODE_MULTIPLIER = 125;
 
 /**
  * Number of pixels the mouse must move before a drag starts.
diff --git a/core/flyout_horizontal.js b/core/flyout_horizontal.js
index ac3c3dc1f..0dad7570c 100644
--- a/core/flyout_horizontal.js
+++ b/core/flyout_horizontal.js
@@ -217,14 +217,10 @@ Blockly.HorizontalFlyout.prototype.scrollToStart = function() {
  * @private
  */
 Blockly.HorizontalFlyout.prototype.wheel_ = function(e) {
-  var delta = e.deltaX || e.deltaY;
+  var scrollDelta = Blockly.utils.getScrollDeltaPixels(e);
+  var delta = scrollDelta.x || scrollDelta.y;
 
   if (delta) {
-    // Firefox's mouse wheel deltas are a tenth that of Chrome/Safari.
-    // DeltaMode is 1 for a mouse wheel, but not for a trackpad scroll event
-    if (goog.userAgent.GECKO && (e.deltaMode === 1)) {
-      delta *= 10;
-    }
     var metrics = this.getMetrics_();
     var pos = metrics.viewLeft + delta;
     var limit = metrics.contentWidth - metrics.viewWidth;
diff --git a/core/flyout_vertical.js b/core/flyout_vertical.js
index 65886f384..3fc36962c 100644
--- a/core/flyout_vertical.js
+++ b/core/flyout_vertical.js
@@ -207,16 +207,11 @@ Blockly.VerticalFlyout.prototype.scrollToStart = function() {
  * @private
  */
 Blockly.VerticalFlyout.prototype.wheel_ = function(e) {
-  var delta = e.deltaY;
+  var scrollDelta = Blockly.utils.getScrollDeltaPixels(e);
 
-  if (delta) {
-    // Firefox's mouse wheel deltas are a tenth that of Chrome/Safari.
-    // DeltaMode is 1 for a mouse wheel, but not for a trackpad scroll event
-    if (goog.userAgent.GECKO && (e.deltaMode === 1)) {
-      delta *= 10;
-    }
+  if (scrollDelta.y) {
     var metrics = this.getMetrics_();
-    var pos = (metrics.viewTop - metrics.contentTop) + delta;
+    var pos = (metrics.viewTop - metrics.contentTop) + scrollDelta.y;
     var limit = metrics.contentHeight - metrics.viewHeight;
     pos = Math.min(pos, limit);
     pos = Math.max(pos, 0);
diff --git a/core/utils.js b/core/utils.js
index 2ec39feee..2d4db0154 100644
--- a/core/utils.js
+++ b/core/utils.js
@@ -304,6 +304,32 @@ Blockly.utils.mouseToSvg = function(e, svg, matrix) {
   return svgPoint.matrixTransform(matrix);
 };
 
+/**
+ * Get the scroll delta of a mouse event in pixel units.
+ * @param {!Event} e Mouse event.
+ * @return {{x: number, y: number}} Scroll delta object with .x and .y
+ *    properties.
+ */
+Blockly.utils.getScrollDeltaPixels = function(e) {
+  switch (e.deltaMode) {
+    case 0x00:  // Pixel mode.
+      return {
+        x: e.deltaX,
+        y: e.deltaY
+      };
+    case 0x01:  // Line mode.
+      return {
+        x: e.deltaX * Blockly.LINE_MODE_MULTIPLIER,
+        y: e.deltaY * Blockly.LINE_MODE_MULTIPLIER
+      };
+    case 0x02:  // Page mode.
+      return {
+        x: e.deltaX * Blockly.PAGE_MODE_MULTIPLIER,
+        y: e.deltaY * Blockly.PAGE_MODE_MULTIPLIER
+      };
+  }
+};
+
 /**
  * Given an array of strings, return the length of the shortest one.
  * @param {!Array.<string>} array Array of strings.
diff --git a/core/workspace_svg.js b/core/workspace_svg.js
index 8a58c9bdc..1ec2c706f 100644
--- a/core/workspace_svg.js
+++ b/core/workspace_svg.js
@@ -1316,27 +1316,24 @@ Blockly.WorkspaceSvg.prototype.onMouseWheel_ = function(e) {
     this.currentGesture_.cancel();
   }
 
-  // TODO (#2301): Change '10' from magic number to constant variable. Also
-  //  change in flyout_vertical.js and flyout_horizontal.js.
-  // Multiplier variable, so that non-pixel-deltaModes are supported.
-  var multiplier = e.deltaMode === 0x1 ? 10 : 1;
 
+  var scrollDelta = Blockly.utils.getScrollDeltaPixels(e);
   if (canWheelZoom && (e.ctrlKey || !canWheelMove)) {
     // The vertical scroll distance that corresponds to a click of a zoom button.
     var PIXELS_PER_ZOOM_STEP = 50;
-    var delta = -e.deltaY / PIXELS_PER_ZOOM_STEP * multiplier;
+    var delta = -scrollDelta.y / PIXELS_PER_ZOOM_STEP;
     var position = Blockly.utils.mouseToSvg(e, this.getParentSvg(),
         this.getInverseScreenCTM());
     this.zoom(position.x, position.y, delta);
   } else {
-    var x = this.scrollX - e.deltaX * multiplier;
-    var y = this.scrollY - e.deltaY * multiplier;
+    var x = this.scrollX - scrollDelta.x;
+    var y = this.scrollY - scrollDelta.y;
 
-    if (e.shiftKey && e.deltaX === 0) {
+    if (e.shiftKey && !scrollDelta.x) {
       // Scroll horizontally (based on vertical scroll delta)
       // This is needed as for some browser/system combinations which do not
       // set deltaX.
-      x = this.scrollX - e.deltaY * multiplier;
+      x = this.scrollX - scrollDelta.y;
       y = this.scrollY; // Don't scroll vertically
     }
     this.scroll(x, y);