diff --git a/qapi/block-core.json b/qapi/block-core.json
index 4bf11e8..c437aa5 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -488,6 +488,31 @@
            '*dirty-bitmaps': ['BlockDirtyInfo'] } }
 
 ##
+# @BlockMeasureInfo:
+#
+# Image file size calculation information.  This structure describes the size
+# requirements for creating a new image file.
+#
+# The size requirements depend on the new image file format.  File size always
+# equals virtual disk size for the 'raw' format, even for sparse POSIX files.
+# Compact formats such as 'qcow2' represent unallocated and zero regions
+# efficiently so file size may be smaller than virtual disk size.
+#
+# The values are upper bounds that are guaranteed to fit the new image file.
+# Subsequent modification, such as internal snapshot or bitmap creation, may
+# require additional space and is not covered here.
+#
+# @required: Size required for a new image file, in bytes.
+#
+# @fully-allocated: Image file size, in bytes, once data has been written
+#                   to all sectors.
+#
+# Since: 2.10
+##
+{ 'struct': 'BlockMeasureInfo',
+  'data': {'required': 'int', 'fully-allocated': 'int'} }
+
+##
 # @query-block:
 #
 # Get a list of BlockInfo for all virtual block devices.