diff --git a/include/rem_aufile.h b/include/rem_aufile.h
index a9a84253f..b76bb0f86 100644
--- a/include/rem_aufile.h
+++ b/include/rem_aufile.h
@@ -25,6 +25,6 @@ int aufile_open(struct aufile **afp, struct aufile_prm *prm,
 int aufile_read(struct aufile *af, uint8_t *p, size_t *sz);
 int aufile_write(struct aufile *af, const uint8_t *p, size_t sz);
 size_t aufile_get_size(struct aufile *af);
-size_t aufile_get_length(struct aufile *af, struct aufile_prm *prm);
+size_t aufile_get_length(struct aufile *af, const struct aufile_prm *prm);
 int aufile_set_position(struct aufile *af, const struct aufile_prm *prm,
 		size_t pos_ms);
diff --git a/rem/aufile/aufile.c b/rem/aufile/aufile.c
index dfa20f796..13f2cd26b 100644
--- a/rem/aufile/aufile.c
+++ b/rem/aufile/aufile.c
@@ -252,26 +252,26 @@ size_t aufile_get_size(struct aufile *af)
  *
  * @return length in ms if success, otherwise 0.
  */
-size_t aufile_get_length(struct aufile *af, struct aufile_prm *prm)
+size_t aufile_get_length(struct aufile *af, const struct aufile_prm *prm)
 {
-	if (!af)
+	if (!af || !prm)
 		return 0;
 
 	switch (prm->fmt) {
 		case AUFMT_PCMA:
 		case AUFMT_PCMU:
-			return af->datasize * prm->channels * prm->srate
-				/ 1000;
+			return af->datasize * 1000 /
+				(prm->channels * prm->srate);
 		case AUFMT_S16LE:
-			return af->datasize * 2 * prm->channels * prm->srate
-				/ 1000;
+			return af->datasize * 1000 /
+				(prm->channels * prm->srate * 2);
 		case AUFMT_S24_3LE:
-			return af->datasize * 3 * prm->channels * prm->srate
-				/ 1000;
+			return af->datasize * 1000 /
+				(prm->channels * prm->srate * 3);
 		case AUFMT_S32LE:
 		case AUFMT_FLOAT:
-			return af->datasize * 4 * prm->channels * prm->srate
-			/ 1000;
+			return af->datasize * 1000 /
+				(prm->channels * prm->srate * 4);
 		default:
 			return 0;
 	}
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index c61cfbb96..9412ac2f5 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -70,6 +70,7 @@ set(SRCS
   aes.c
   async.c
   aubuf.c
+  aulength.c
   aulevel.c
   auresamp.c
   av1.c
diff --git a/test/aulength.c b/test/aulength.c
new file mode 100644
index 000000000..2b4f8f5b2
--- /dev/null
+++ b/test/aulength.c
@@ -0,0 +1,36 @@
+/**
+ * @file src/aulength.c audio file duration test
+ *
+ * Copyright (C) 2023 Lars Immisch
+ */
+
+#include <re.h>
+#include <rem.h>
+#include "test.h"
+
+
+#define DEBUG_MODULE "aulength"
+#define DEBUG_LEVEL 5
+#include <re_dbg.h>
+
+
+int test_aulength(void)
+{
+	struct aufile *af = NULL;
+	struct aufile_prm prm;
+	char path[256];
+
+	re_snprintf(path, sizeof(path), "%s/beep.wav", test_datapath());
+
+	int err = aufile_open(&af, &prm, path, AUFILE_READ);
+	if (err)
+		TEST_ERR(err);
+
+	size_t length = aufile_get_length(af, &prm);
+	TEST_EQUALS(67, length);
+
+out:
+	mem_deref(af);
+
+	return err;
+}
diff --git a/test/data/beep.wav b/test/data/beep.wav
new file mode 100644
index 000000000..a148a48ae
Binary files /dev/null and b/test/data/beep.wav differ
diff --git a/test/test.c b/test/test.c
index 039dd6894..ca71e99a7 100644
--- a/test/test.c
+++ b/test/test.c
@@ -53,6 +53,7 @@ static const struct test tests[] = {
 	TEST(test_aes),
 	TEST(test_aes_gcm),
 	TEST(test_aubuf),
+	TEST(test_aulength),
 	TEST(test_aulevel),
 	TEST(test_auresamp),
 	TEST(test_async),
diff --git a/test/test.h b/test/test.h
index ee386b5e9..306d9bf47 100644
--- a/test/test.h
+++ b/test/test.h
@@ -159,6 +159,7 @@ int test_aes(void);
 int test_aes_gcm(void);
 int test_aubuf(void);
 int test_aulevel(void);
+int test_aulength(void);
 int test_auresamp(void);
 int test_async(void);
 int test_av1(void);