diff --git a/packages/flutter/lib/src/material/scaffold.dart b/packages/flutter/lib/src/material/scaffold.dart
index 42a5c94af5..7859eacbd4 100644
--- a/packages/flutter/lib/src/material/scaffold.dart
+++ b/packages/flutter/lib/src/material/scaffold.dart
@@ -409,6 +409,7 @@ class _ScaffoldLayout extends MultiChildLayoutDelegate {
     @required this.floatingActionButtonMoveAnimationProgress,
     @required this.floatingActionButtonMotionAnimator,
     @required this.isSnackBarFloating,
+    @required this.snackBarWidth,
     @required this.extendBody,
     @required this.extendBodyBehindAppBar,
   }) : assert(minInsets != null),
@@ -432,6 +433,7 @@ class _ScaffoldLayout extends MultiChildLayoutDelegate {
   final FloatingActionButtonAnimator floatingActionButtonMotionAnimator;
 
   final bool isSnackBarFloating;
+  final double snackBarWidth;
 
   @override
   void performLayout(Size size) {
@@ -563,8 +565,12 @@ class _ScaffoldLayout extends MultiChildLayoutDelegate {
     }
 
     if (hasChild(_ScaffoldSlot.snackBar)) {
+      final bool hasCustomWidth = snackBarWidth != null && snackBarWidth < size.width;
       if (snackBarSize == Size.zero) {
-        snackBarSize = layoutChild(_ScaffoldSlot.snackBar, fullWidthConstraints);
+        snackBarSize = layoutChild(
+          _ScaffoldSlot.snackBar,
+          hasCustomWidth ? looseConstraints : fullWidthConstraints,
+        );
       }
 
       double snackBarYOffsetBase;
@@ -574,7 +580,8 @@ class _ScaffoldLayout extends MultiChildLayoutDelegate {
         snackBarYOffsetBase = contentBottom;
       }
 
-      positionChild(_ScaffoldSlot.snackBar, Offset(0.0, snackBarYOffsetBase - snackBarSize.height));
+      final double xOffset = hasCustomWidth ? (size.width - snackBarWidth) / 2 : 0.0;
+      positionChild(_ScaffoldSlot.snackBar, Offset(xOffset, snackBarYOffsetBase - snackBarSize.height));
     }
 
     if (hasChild(_ScaffoldSlot.statusBar)) {
@@ -2381,11 +2388,13 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
     }
 
     bool isSnackBarFloating = false;
+    double snackBarWidth;
     if (_snackBars.isNotEmpty) {
       final SnackBarBehavior snackBarBehavior = _snackBars.first._widget.behavior
         ?? themeData.snackBarTheme.behavior
         ?? SnackBarBehavior.fixed;
       isSnackBarFloating = snackBarBehavior == SnackBarBehavior.floating;
+      snackBarWidth = _snackBars.first._widget.width;
 
       _addIfNonNull(
         children,
@@ -2541,6 +2550,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
                 previousFloatingActionButtonLocation: _previousFloatingActionButtonLocation,
                 textDirection: textDirection,
                 isSnackBarFloating: isSnackBarFloating,
+                snackBarWidth: snackBarWidth,
               ),
             );
           }),
diff --git a/packages/flutter/lib/src/material/snack_bar.dart b/packages/flutter/lib/src/material/snack_bar.dart
index cd114c5adb..07373d0923 100644
--- a/packages/flutter/lib/src/material/snack_bar.dart
+++ b/packages/flutter/lib/src/material/snack_bar.dart
@@ -173,6 +173,9 @@ class SnackBar extends StatefulWidget {
     @required this.content,
     this.backgroundColor,
     this.elevation,
+    this.margin,
+    this.padding,
+    this.width,
     this.shape,
     this.behavior,
     this.action,
@@ -181,6 +184,18 @@ class SnackBar extends StatefulWidget {
     this.onVisible,
   }) : assert(elevation == null || elevation >= 0.0),
        assert(content != null),
+       assert(
+         margin == null || behavior == SnackBarBehavior.floating,
+         'Margin can only be used with floating behavior',
+       ),
+       assert(
+         width == null || behavior == SnackBarBehavior.floating,
+         'Width can only be used with floating behavior',
+       ),
+       assert(
+         width == null || margin == null,
+         'Width and margin can not be used together',
+       ),
        assert(duration != null),
        super(key: key);
 
@@ -189,7 +204,7 @@ class SnackBar extends StatefulWidget {
   /// Typically a [Text] widget.
   final Widget content;
 
-  /// The Snackbar's background color. If not specified it will use
+  /// The snack bar's background color. If not specified it will use
   /// [ThemeData.snackBarTheme.backgroundColor]. If that is not specified
   /// it will default to a dark variation of [ColorScheme.surface] for light
   /// themes, or [ColorScheme.onSurface] for dark themes.
@@ -204,6 +219,34 @@ class SnackBar extends StatefulWidget {
   /// used, if that is also null, the default value is 6.0.
   final double elevation;
 
+  /// Empty space to surround the snack bar.
+  ///
+  /// This property is only used when [behavior] is [SnackBarBehavior.floating].
+  /// It can not be used if [width] is specified.
+  ///
+  /// If this property is null, then the default is
+  /// `EdgeInsets.fromLTRB(15.0, 5.0, 15.0, 10.0)`.
+  final EdgeInsetsGeometry margin;
+
+  /// The amount of padding to apply to the snack bar's content and optional
+  /// action.
+  ///
+  /// If this property is null, then the default depends on the [behavior] and
+  /// the presence of an [action]. The start padding is 24 if [behavior] is
+  /// [SnackBarBehavior.fixed] and 16 if it is [SnackBarBehavior.floating]. If
+  /// there is no [action], the same padding is added to the end.
+  final EdgeInsetsGeometry padding;
+
+  /// The width of the snack bar.
+  ///
+  /// If width is specified, the snack bar will be centered horizontally in the
+  /// available space. This property is only used when [behavior] is
+  /// [SnackBarBehavior.floating]. It can not be used if [margin] is specified.
+  ///
+  /// If this property is null, then the snack bar will take up the full device
+  /// width less the margin.
+  final double width;
+
   /// The shape of the snack bar's [Material].
   ///
   /// Defines the snack bar's [Material.shape].
@@ -272,6 +315,9 @@ class SnackBar extends StatefulWidget {
       content: content,
       backgroundColor: backgroundColor,
       elevation: elevation,
+      margin: margin,
+      padding: padding,
+      width: width,
       shape: shape,
       behavior: behavior,
       action: action,
@@ -365,7 +411,9 @@ class _SnackBarState extends State<SnackBar> {
     final TextStyle contentTextStyle = snackBarTheme.contentTextStyle ?? inverseTheme.textTheme.subtitle1;
     final SnackBarBehavior snackBarBehavior = widget.behavior ?? snackBarTheme.behavior ?? SnackBarBehavior.fixed;
     final bool isFloatingSnackBar = snackBarBehavior == SnackBarBehavior.floating;
-    final double snackBarPadding = isFloatingSnackBar ? 16.0 : 24.0;
+    final double horizontalPadding = isFloatingSnackBar ? 16.0 : 24.0;
+    final EdgeInsetsGeometry padding = widget.padding
+      ?? EdgeInsetsDirectional.only(start: horizontalPadding, end: widget.action != null ? 0 : horizontalPadding);
 
     final CurvedAnimation heightAnimation = CurvedAnimation(parent: widget.animation, curve: _snackBarHeightCurve);
     final CurvedAnimation fadeInAnimation = CurvedAnimation(parent: widget.animation, curve: _snackBarFadeInCurve);
@@ -375,13 +423,11 @@ class _SnackBarState extends State<SnackBar> {
       reverseCurve: const Threshold(0.0),
     );
 
-    Widget snackBar = SafeArea(
-      top: false,
-      bottom: !isFloatingSnackBar,
+    Widget snackBar = Padding(
+      padding: padding,
       child: Row(
         crossAxisAlignment: CrossAxisAlignment.center,
         children: <Widget>[
-          SizedBox(width: snackBarPadding),
           Expanded(
             child: Container(
               padding: const EdgeInsets.symmetric(vertical: _singleLineVerticalPadding),
@@ -395,15 +441,20 @@ class _SnackBarState extends State<SnackBar> {
             ButtonTheme(
               textTheme: ButtonTextTheme.accent,
               minWidth: 64.0,
-              padding: EdgeInsets.symmetric(horizontal: snackBarPadding),
+              padding: EdgeInsets.symmetric(horizontal: horizontalPadding),
               child: widget.action,
-            )
-          else
-            SizedBox(width: snackBarPadding),
+            ),
         ],
       ),
     );
 
+    if (!isFloatingSnackBar) {
+      snackBar = SafeArea(
+        top: false,
+        child: snackBar,
+      );
+    }
+
     final double elevation = widget.elevation ?? snackBarTheme.elevation ?? 6.0;
     final Color backgroundColor = widget.backgroundColor ?? snackBarTheme.backgroundColor ?? inverseTheme.backgroundColor;
     final ShapeBorder shape = widget.shape
@@ -426,8 +477,30 @@ class _SnackBarState extends State<SnackBar> {
     );
 
     if (isFloatingSnackBar) {
-      snackBar = Padding(
-        padding: const EdgeInsets.fromLTRB(15.0, 5.0, 15.0, 10.0),
+      const double topMargin = 5.0;
+      const double bottomMargin = 10.0;
+      // If width is provided, do not include horizontal margins.
+      if (widget.width != null) {
+        snackBar = Container(
+          margin: const EdgeInsets.only(top: topMargin, bottom: bottomMargin),
+          width: widget.width,
+          child: snackBar,
+        );
+      } else {
+        const double horizontalMargin = 15.0;
+        snackBar = Padding(
+          padding: widget.margin ?? const EdgeInsets.fromLTRB(
+            horizontalMargin,
+            topMargin,
+            horizontalMargin,
+            bottomMargin,
+          ),
+          child: snackBar,
+        );
+      }
+      snackBar = SafeArea(
+        top: false,
+        bottom: false,
         child: snackBar,
       );
     }
diff --git a/packages/flutter/test/material/snack_bar_test.dart b/packages/flutter/test/material/snack_bar_test.dart
index 5275d2a210..9946603357 100644
--- a/packages/flutter/test/material/snack_bar_test.dart
+++ b/packages/flutter/test/material/snack_bar_test.dart
@@ -380,6 +380,129 @@ void main() {
     expect(renderModel.color, equals(darkTheme.colorScheme.onSurface));
   });
 
+  testWidgets('Snackbar margin can be customized', (WidgetTester tester) async {
+    const double padding = 20.0;
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: Builder(
+              builder: (BuildContext context) {
+                return GestureDetector(
+                  onTap: () {
+                    Scaffold.of(context).showSnackBar(
+                      SnackBar(
+                        content: const Text('I am a snack bar.'),
+                        margin: const EdgeInsets.all(padding),
+                        behavior: SnackBarBehavior.floating,
+                      ),
+                    );
+                  },
+                  child: const Text('X'),
+                );
+              }
+          ),
+        ),
+      ),
+    );
+
+    await tester.tap(find.text('X'));
+    await tester.pump(); // start animation
+    await tester.pump(const Duration(milliseconds: 750));
+
+    final Finder materialFinder = find.descendant(
+      of: find.byType(SnackBar),
+      matching: find.byType(Material),
+    );
+    final Offset snackBarBottomLeft = tester.getBottomLeft(materialFinder);
+    final Offset snackBarBottomRight = tester.getBottomRight(materialFinder);
+    expect(snackBarBottomLeft.dx, padding);
+    expect(snackBarBottomLeft.dy, 600 - padding); // Device height is 600.
+    expect(snackBarBottomRight.dx, 800 - padding); // Device width is 800.
+  });
+
+  testWidgets('Snackbar padding can be customized', (WidgetTester tester) async {
+    const double padding = 20.0;
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: Builder(
+              builder: (BuildContext context) {
+                return GestureDetector(
+                  onTap: () {
+                    Scaffold.of(context).showSnackBar(
+                      const SnackBar(
+                        content: Text('I am a snack bar.'),
+                        padding: EdgeInsets.all(padding),
+                      ),
+                    );
+                  },
+                  child: const Text('X'),
+                );
+              }
+          ),
+        ),
+      ),
+    );
+
+    await tester.tap(find.text('X'));
+    await tester.pump(); // start animation
+    await tester.pump(const Duration(milliseconds: 750));
+
+    final Finder textFinder = find.text('I am a snack bar.');
+    final Finder materialFinder = find.descendant(
+      of: find.byType(SnackBar),
+      matching: find.byType(Material),
+    );
+    final Offset textBottomLeft = tester.getBottomLeft(textFinder);
+    final Offset textTopRight = tester.getTopRight(textFinder);
+    final Offset snackBarBottomLeft = tester.getBottomLeft(materialFinder);
+    final Offset snackBarTopRight = tester.getTopRight(materialFinder);
+    expect(textBottomLeft.dx - snackBarBottomLeft.dx, padding);
+    expect(snackBarTopRight.dx - textTopRight.dx, padding);
+    // The text is given a vertical padding of 14 already.
+    expect(snackBarBottomLeft.dy - textBottomLeft.dy, padding + 14);
+    expect(textTopRight.dy - snackBarTopRight.dy, padding + 14);
+  });
+
+  testWidgets('Snackbar width can be customized', (WidgetTester tester) async {
+    const double width = 200.0;
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: Builder(
+              builder: (BuildContext context) {
+                return GestureDetector(
+                  onTap: () {
+                    Scaffold.of(context).showSnackBar(
+                      SnackBar(
+                        content: const Text('I am a snack bar.'),
+                        width: width,
+                        behavior: SnackBarBehavior.floating,
+                      ),
+                    );
+                  },
+                  child: const Text('X'),
+                );
+              }
+          ),
+        ),
+      ),
+    );
+
+    await tester.tap(find.text('X'));
+    await tester.pump(); // start animation
+    await tester.pump(const Duration(milliseconds: 750));
+
+    final Finder materialFinder = find.descendant(
+      of: find.byType(SnackBar),
+      matching: find.byType(Material),
+    );
+    final Offset snackBarBottomLeft = tester.getBottomLeft(materialFinder);
+    final Offset snackBarBottomRight = tester.getBottomRight(materialFinder);
+    expect(snackBarBottomLeft.dx, (800 - width) / 2); // Device width is 800.
+    expect(snackBarBottomRight.dx, (800 + width) / 2); // Device width is 800.
+  });
+
   testWidgets('Snackbar labels can be colored', (WidgetTester tester) async {
     await tester.pumpWidget(
       MaterialApp(