diff --git a/src/switch_core_io.c b/src/switch_core_io.c
index 8b12efaffb..fd11a3da47 100644
--- a/src/switch_core_io.c
+++ b/src/switch_core_io.c
@@ -1127,6 +1127,9 @@ SWITCH_DECLARE(switch_status_t) switch_core_session_send_dtmf_string(switch_core
 	int i, argc;
 	char *argv[256];
 	int dur_total = 0;
+	int rate_mult = 8;
+
+	switch_codec_implementation_t write_impl = { 0 };
 
 	switch_assert(session != NULL);
 
@@ -1156,13 +1159,16 @@ SWITCH_DECLARE(switch_status_t) switch_core_session_send_dtmf_string(switch_core
 		switch_channel_pre_answer(session->channel);
 	}
 
+	switch_core_session_get_write_impl(session, &write_impl);
+	rate_mult = (write_impl.actual_samples_per_second / 1000);
+
 	for (i = 0; i < argc; i++) {
 		dtmf.duration = switch_core_default_dtmf_duration(0);
-		dur = switch_core_default_dtmf_duration(0) / 8;
+		dur = switch_core_default_dtmf_duration(0) / rate_mult;
 		if ((p = strchr(argv[i], '@'))) {
 			*p++ = '\0';
-			if ((dur = atoi(p)) > (int)switch_core_min_dtmf_duration(0) / 8) {
-				dtmf.duration = dur * 8;
+			if ((dur = atoi(p)) > (int)switch_core_min_dtmf_duration(0) / rate_mult) {
+				dtmf.duration = dur * rate_mult;
 			}
 		}
 
@@ -1192,14 +1198,14 @@ SWITCH_DECLARE(switch_status_t) switch_core_session_send_dtmf_string(switch_core
 					switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(session), SWITCH_LOG_DEBUG, "%s send dtmf\ndigit=%c ms=%u samples=%u\n",
 									  switch_channel_get_name(session->channel), dtmf.digit, dur, dtmf.duration);
 					sent++;
-					dur_total += dtmf.duration + 2000;	/* account for 250ms pause */
+					dur_total += dtmf.duration + (250 * rate_mult);	/* account for 250ms pause */
 				}
 			}
 		}
 
 		if (dur_total) {
 			char tmp[32] = "";
-			switch_snprintf(tmp, sizeof(tmp), "%d", dur_total / 8);
+			switch_snprintf(tmp, sizeof(tmp), "%d", dur_total / rate_mult);
 			switch_channel_set_variable(session->channel, "last_dtmf_duration", tmp);
 		}