diff --git a/shared/timespec-util.h b/shared/timespec-util.h
index 958adb05..576b3e8f 100644
--- a/shared/timespec-util.h
+++ b/shared/timespec-util.h
@@ -93,6 +93,20 @@ timespec_to_nsec(const struct timespec *a)
 	return (int64_t)a->tv_sec * NSEC_PER_SEC + a->tv_nsec;
 }
 
+/* Subtract timespecs and return result in nanoseconds
+ *
+ * \param a[in] operand
+ * \param b[in] operand
+ * \return to_nanoseconds(a - b)
+ */
+static inline int64_t
+timespec_sub_to_nsec(const struct timespec *a, const struct timespec *b)
+{
+	struct timespec r;
+	timespec_sub(&r, a, b);
+	return timespec_to_nsec(&r);
+}
+
 /* Convert timespec to milliseconds
  *
  * \param a timespec
@@ -106,6 +120,18 @@ timespec_to_msec(const struct timespec *a)
 	return (int64_t)a->tv_sec * 1000 + a->tv_nsec / 1000000;
 }
 
+/* Subtract timespecs and return result in milliseconds
+ *
+ * \param a[in] operand
+ * \param b[in] operand
+ * \return to_milliseconds(a - b)
+ */
+static inline int64_t
+timespec_sub_to_msec(const struct timespec *a, const struct timespec *b)
+{
+	return timespec_sub_to_nsec(a, b) / 1000000;
+}
+
 /* Convert milli-Hertz to nanoseconds
  *
  * \param mhz frequency in mHz, not zero
diff --git a/tests/timespec-test.c b/tests/timespec-test.c
index 712d1acd..a5039110 100644
--- a/tests/timespec-test.c
+++ b/tests/timespec-test.c
@@ -142,3 +142,25 @@ ZUC_TEST(timespec_test, timespec_add_msec)
 	ZUC_ASSERT_EQ(1002, r.tv_sec);
 	ZUC_ASSERT_EQ(2000001, r.tv_nsec);
 }
+
+ZUC_TEST(timespec_test, timespec_sub_to_nsec)
+{
+	struct timespec a, b;
+
+	a.tv_sec = 1000;
+	a.tv_nsec = 1;
+	b.tv_sec = 1;
+	b.tv_nsec = 2;
+	ZUC_ASSERT_EQ((999L * NSEC_PER_SEC) - 1, timespec_sub_to_nsec(&a, &b));
+}
+
+ZUC_TEST(timespec_test, timespec_sub_to_msec)
+{
+	struct timespec a, b;
+
+	a.tv_sec = 1000;
+	a.tv_nsec = 2000000L;
+	b.tv_sec = 2;
+	b.tv_nsec = 1000000L;
+	ZUC_ASSERT_EQ((998 * 1000) + 1, timespec_sub_to_msec(&a, &b));
+}