diff --git a/utils/src/bloom.c b/utils/src/bloom.c
new file mode 100644
index 00000000..45939424
--- /dev/null
+++ b/utils/src/bloom.c
@@ -0,0 +1,20 @@
+#include <errno.h>
+
+#include "sparse.h"
+#include "util.h"
+#include "format.h"
+#include "hash.h"
+#include "bloom.h"
+
+void calc_bloom_nrs(struct scoutfs_key *key, unsigned int *nrs)
+{
+	u64 hash;
+	int i;
+
+	hash = scoutfs_hash64(key, sizeof(struct scoutfs_key));
+
+	for (i = 0; i < SCOUTFS_FOREST_BLOOM_NRS; i++) {
+		nrs[i] = (u32)hash % SCOUTFS_FOREST_BLOOM_BITS;
+		hash >>= SCOUTFS_FOREST_BLOOM_FUNC_BITS;
+	}
+}
diff --git a/utils/src/bloom.h b/utils/src/bloom.h
new file mode 100644
index 00000000..9a2d3b3b
--- /dev/null
+++ b/utils/src/bloom.h
@@ -0,0 +1,6 @@
+#ifndef _BLOOM_H_
+#define _BLOOM_H_
+
+void calc_bloom_nrs(struct scoutfs_key *key, unsigned int *nrs);
+
+#endif