diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index fa45f774d7..5c47611b4a 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -344,12 +344,12 @@ static int expand_atom(struct strbuf *sb, const char *atom, int len,
 		if (data->mark_query)
 			data->info.sizep = &data->size;
 		else
-			strbuf_addf(sb, "%"PRIuMAX , (uintmax_t)data->size);
+			strbuf_add_uint(sb, data->size);
 	} else if (is_atom("objectsize:disk", atom, len)) {
 		if (data->mark_query)
 			data->info.disk_sizep = &data->disk_size;
 		else
-			strbuf_addf(sb, "%"PRIuMAX, (uintmax_t)data->disk_size);
+			strbuf_add_uint(sb, data->disk_size);
 	} else if (is_atom("rest", atom, len)) {
 		if (data->mark_query)
 			data->split_on_whitespace = 1;
diff --git a/builtin/ls-files.c b/builtin/ls-files.c
index e1a22b41b9..12d5d828ff 100644
--- a/builtin/ls-files.c
+++ b/builtin/ls-files.c
@@ -250,20 +250,23 @@ static void expand_objectsize(struct repository *repo, struct strbuf *line,
 			      const struct object_id *oid,
 			      const enum object_type type, unsigned int padded)
 {
+	static const char padding[] = "       ";
+	size_t min_len = padded ? strlen(padding) : 0;
+	size_t orig_len = line->len;
+	size_t len;
+
 	if (type == OBJ_BLOB) {
 		unsigned long size;
 		if (odb_read_object_info(repo->objects, oid, &size) < 0)
 			die(_("could not get object info about '%s'"),
 			    oid_to_hex(oid));
-		if (padded)
-			strbuf_addf(line, "%7"PRIuMAX, (uintmax_t)size);
-		else
-			strbuf_addf(line, "%"PRIuMAX, (uintmax_t)size);
-	} else if (padded) {
-		strbuf_addf(line, "%7s", "-");
+		strbuf_add_uint(line, size);
 	} else {
 		strbuf_addstr(line, "-");
 	}
+	len = line->len - orig_len;
+	if (len < min_len)
+		strbuf_insert(line, orig_len, padding, min_len - len);
 }
 
 static void show_ce_fmt(struct repository *repo, const struct cache_entry *ce,
diff --git a/builtin/ls-tree.c b/builtin/ls-tree.c
index 113e4a960d..57846911ce 100644
--- a/builtin/ls-tree.c
+++ b/builtin/ls-tree.c
@@ -26,20 +26,23 @@ static const char * const ls_tree_usage[] = {
 static void expand_objectsize(struct strbuf *line, const struct object_id *oid,
 			      const enum object_type type, unsigned int padded)
 {
+	static const char padding[] = "       ";
+	size_t min_len = padded ? strlen(padding) : 0;
+	size_t orig_len = line->len;
+	size_t len;
+
 	if (type == OBJ_BLOB) {
 		unsigned long size;
 		if (odb_read_object_info(the_repository->objects, oid, &size) < 0)
 			die(_("could not get object info about '%s'"),
 			    oid_to_hex(oid));
-		if (padded)
-			strbuf_addf(line, "%7"PRIuMAX, (uintmax_t)size);
-		else
-			strbuf_addf(line, "%"PRIuMAX, (uintmax_t)size);
-	} else if (padded) {
-		strbuf_addf(line, "%7s", "-");
+		strbuf_add_uint(line, size);
 	} else {
 		strbuf_addstr(line, "-");
 	}
+	len = line->len - orig_len;
+	if (len < min_len)
+		strbuf_insert(line, orig_len, padding, min_len - len);
 }
 
 struct ls_tree_options {
diff --git a/strbuf.c b/strbuf.c
index 8610965d53..764b629927 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -359,6 +359,18 @@ void strbuf_addf(struct strbuf *sb, const char *fmt, ...)
 	va_end(ap);
 }
 
+void strbuf_add_uint(struct strbuf *sb, uintmax_t value)
+{
+	char buf[DIV_ROUND_UP(bitsizeof(value) * 10, 33)];
+	char *end = buf + sizeof(buf);
+	char *p = end;
+
+	do
+		*--p = "0123456789"[value % 10];
+	while (value /= 10);
+	strbuf_add(sb, p, end - p);
+}
+
 static void add_lines(struct strbuf *out,
 			const char *prefix,
 			const char *buf, size_t size,
diff --git a/strbuf.h b/strbuf.h
index 06e284f9cc..1089ae687b 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -410,6 +410,12 @@ void strbuf_humanise_rate(struct strbuf *buf, off_t bytes);
 __attribute__((format (printf,2,3)))
 void strbuf_addf(struct strbuf *sb, const char *fmt, ...);
 
+
+/**
+ * Add an unsigned decimal number.
+ */
+void strbuf_add_uint(struct strbuf *sb, uintmax_t value);
+
 /**
  * Add a formatted string prepended by a comment character and a
  * blank to the buffer.