diff --git a/packages/block-library/src/cover/style.scss b/packages/block-library/src/cover/style.scss
index c19659cbb9f94a..0cbb6d289921ce 100644
--- a/packages/block-library/src/cover/style.scss
+++ b/packages/block-library/src/cover/style.scss
@@ -10,6 +10,8 @@
 	justify-content: center;
 	align-items: center;
 	padding: 1em;
+	// This block has customizable padding, border-box makes that more predictable.
+	box-sizing: border-box;
 
 	&.has-parallax {
 		background-attachment: fixed;
diff --git a/packages/block-library/src/group/style.scss b/packages/block-library/src/group/style.scss
new file mode 100644
index 00000000000000..3457a12adb6221
--- /dev/null
+++ b/packages/block-library/src/group/style.scss
@@ -0,0 +1,4 @@
+.wp-block-group {
+	// This block has customizable padding, border-box makes that more predictable.
+	box-sizing: border-box;
+}
diff --git a/packages/block-library/src/style.scss b/packages/block-library/src/style.scss
index d4e19def2efd8f..653393dc488a91 100644
--- a/packages/block-library/src/style.scss
+++ b/packages/block-library/src/style.scss
@@ -13,6 +13,7 @@
 @import "./embed/style.scss";
 @import "./file/style.scss";
 @import "./gallery/style.scss";
+@import "./group/style.scss";
 @import "./heading/style.scss";
 @import "./image/style.scss";
 @import "./latest-comments/style.scss";