diff --git a/utils/man/scoutfs.8 b/utils/man/scoutfs.8
index 4664f14a..e397f724 100644
--- a/utils/man/scoutfs.8
+++ b/utils/man/scoutfs.8
@@ -184,6 +184,11 @@ elected servers race to fence each other and can have the unlikely
 outcome of continually racing to fence each other resulting in a
 persistent loss of service.
 .TP
+.B "-S 4KB_blocks"
+Limit the device size used by the filesystem to the given size in units
+of 4KB blocks.  It must be larger than the mkfs minimum size and fit
+within the device.
+.TP
 .B "path"
 The path to the device whose contents will be unconditionally destroyed.
 .RE
diff --git a/utils/src/mkfs.c b/utils/src/mkfs.c
index 71903a00..b03b33d5 100644
--- a/utils/src/mkfs.c
+++ b/utils/src/mkfs.c
@@ -21,6 +21,7 @@
 #include "cmd.h"
 #include "util.h"
 #include "format.h"
+#include "parse.h"
 #include "crc.h"
 #include "rand.h"
 #include "dev.h"
@@ -132,7 +133,7 @@ static int write_alloc_root(struct scoutfs_super_block *super, int fd,
  *  - btree ring blocks with manifest and allocator btree blocks
  *  - segment with root inode items
  */
-static int write_new_fs(char *path, int fd, u8 quorum_count)
+static int write_new_fs(char *path, int fd, u8 quorum_count, u64 dev_blocks)
 {
 	struct scoutfs_super_block *super;
 	struct scoutfs_inode inode;
@@ -173,6 +174,16 @@ static int write_new_fs(char *path, int fd, u8 quorum_count)
 		goto out;
 	}
 
+	if (dev_blocks > 0 && size < (dev_blocks << SCOUTFS_BLOCK_SM_SHIFT)) {
+		fprintf(stderr, "device size limit %llu in 4KB blocks given with -S is greater than device byte size %llu\n",
+			dev_blocks, size);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (dev_blocks > 0 && size > (dev_blocks << SCOUTFS_BLOCK_SM_SHIFT))
+		size = dev_blocks << SCOUTFS_BLOCK_SM_SHIFT;
+
 	/* arbitrarily require a reasonably large device */
 	limit = 8ULL * (1024 * 1024 * 1024);
 	if (size < limit) {
@@ -369,12 +380,13 @@ static int mkfs_func(int argc, char *argv[])
 	unsigned long long ull;
 	char *path = argv[1];
 	u8 quorum_count = 0;
+	u64 dev_blocks = 0;
 	char *end = NULL;
 	int ret;
 	int fd;
 	int c;
 
-	while ((c = getopt_long(argc, argv, "Q:", long_ops, NULL)) != -1) {
+	while ((c = getopt_long(argc, argv, "Q:S:", long_ops, NULL)) != -1) {
 		switch (c) {
 		case 'Q':
 			ull = strtoull(optarg, &end, 0);
@@ -386,6 +398,14 @@ static int mkfs_func(int argc, char *argv[])
 			}
 			quorum_count = ull;
 			break;
+		case 'S':
+			ret = parse_u64(optarg, &dev_blocks);
+			if (ret < 0) {
+				printf("scoutfs: invalid device blocks count '%s'\n",
+					optarg);
+				return ret;
+			}
+			break;
 		case '?':
 		default:
 			return -EINVAL;
@@ -412,7 +432,7 @@ static int mkfs_func(int argc, char *argv[])
 		return ret;
 	}
 
-	ret = write_new_fs(path, fd, quorum_count);
+	ret = write_new_fs(path, fd, quorum_count, dev_blocks);
 	close(fd);
 
 	return ret;