diff --git a/arena.h b/arena.h
index 410bae6..82f35ad 100644
--- a/arena.h
+++ b/arena.h
@@ -75,6 +75,7 @@ void *arena_memdup(Arena *a, void *data, size_t size);
 char *arena_sprintf(Arena *a, const char *format, ...);
 #endif // ARENA_NOSTDIO
 
+size_t arena_bytes(Arena *a);
 void arena_reset(Arena *a);
 void arena_free(Arena *a);
 
@@ -278,6 +279,14 @@ char *arena_sprintf(Arena *a, const char *format, ...)
 }
 #endif // ARENA_NOSTDIO
 
+size_t arena_bytes(Arena *a) {
+	size_t bytes_total = 0;
+	for (Region* r = a->begin; r != NULL; r = r->next) {
+		bytes_total += r->count * sizeof(uintptr_t);
+	}
+	return bytes_total;
+}
+
 void arena_reset(Arena *a)
 {
     for (Region *r = a->begin; r != NULL; r = r->next) {