diff --git a/openless-all/app/src-tauri/src/asr/local/foundry_provider.rs b/openless-all/app/src-tauri/src/asr/local/foundry_provider.rs
index c8f26495..ef09d88d 100644
--- a/openless-all/app/src-tauri/src/asr/local/foundry_provider.rs
+++ b/openless-all/app/src-tauri/src/asr/local/foundry_provider.rs
@@ -148,7 +148,7 @@ impl crate::recorder::AudioConsumer for FoundryLocalWhisperAsr {
 }
 
 fn pcm_duration_ms(pcm: &[u8]) -> u64 {
-    (pcm.len() as u64 / 2) * 1000 / 16_000
+    crate::asr::pcm::pcm_duration_ms(pcm)
 }
 
 fn pcm_to_wav(pcm: &[u8]) -> Vec<u8> {
diff --git a/openless-all/app/src-tauri/src/asr/local/sherpa_provider.rs b/openless-all/app/src-tauri/src/asr/local/sherpa_provider.rs
index 06016197..210fd2a3 100644
--- a/openless-all/app/src-tauri/src/asr/local/sherpa_provider.rs
+++ b/openless-all/app/src-tauri/src/asr/local/sherpa_provider.rs
@@ -222,11 +222,11 @@ impl crate::recorder::AudioConsumer for SherpaOnnxAsr {
 }
 
 fn pcm_duration_ms(pcm: &[u8]) -> u64 {
-    pcm_duration_ms_from_bytes(pcm.len() as u64)
+    crate::asr::pcm::pcm_duration_ms(pcm)
 }
 
 fn pcm_duration_ms_from_bytes(bytes: u64) -> u64 {
-    (bytes / 2) * 1000 / 16_000
+    crate::asr::pcm::pcm_duration_ms_from_bytes(bytes)
 }
 
 fn trim_transcript_text(text: &str) -> String {
diff --git a/openless-all/app/src-tauri/src/asr/local/sherpa_runtime.rs b/openless-all/app/src-tauri/src/asr/local/sherpa_runtime.rs
index ec56538c..ed808c05 100644
--- a/openless-all/app/src-tauri/src/asr/local/sherpa_runtime.rs
+++ b/openless-all/app/src-tauri/src/asr/local/sherpa_runtime.rs
@@ -485,7 +485,7 @@ fn accumulate_dir_size(dir: &Path, bytes: &mut u64) {
 }
 
 fn pcm_duration_ms(pcm: &[u8]) -> u64 {
-    (pcm.len() as u64 / 2) * 1000 / 16_000
+    crate::asr::pcm::pcm_duration_ms(pcm)
 }
 
 enum LoadedModel {
diff --git a/openless-all/app/src-tauri/src/asr/mimo.rs b/openless-all/app/src-tauri/src/asr/mimo.rs
index 5637107d..1fe68522 100644
--- a/openless-all/app/src-tauri/src/asr/mimo.rs
+++ b/openless-all/app/src-tauri/src/asr/mimo.rs
@@ -178,7 +178,7 @@ pub fn extract_mimo_text(json: &Value) -> String {
 }
 
 fn pcm_duration_ms(pcm: &[u8]) -> u64 {
-    (pcm.len() as u64 / PCM_BYTES_PER_SAMPLE as u64) * 1000 / PCM_SAMPLE_RATE_HZ
+    super::pcm::pcm_duration_ms(pcm)
 }
 
 fn split_pcm_by_duration(pcm: &[u8], max_chunk_duration_ms: u64) -> Vec<&[u8]> {
diff --git a/openless-all/app/src-tauri/src/asr/mod.rs b/openless-all/app/src-tauri/src/asr/mod.rs
index 1b51857f..e1c761c4 100644
--- a/openless-all/app/src-tauri/src/asr/mod.rs
+++ b/openless-all/app/src-tauri/src/asr/mod.rs
@@ -9,6 +9,7 @@ pub mod bailian;
 mod frame;
 pub mod local;
 pub mod mimo;
+pub mod pcm;
 pub mod volcengine;
 pub mod wav;
 pub mod whisper;
diff --git a/openless-all/app/src-tauri/src/asr/pcm.rs b/openless-all/app/src-tauri/src/asr/pcm.rs
new file mode 100644
index 00000000..1c4b2865
--- /dev/null
+++ b/openless-all/app/src-tauri/src/asr/pcm.rs
@@ -0,0 +1,38 @@
+//! 共享 PCM 时长计算。
+//!
+//! 录音统一是 16 kHz / 单声道 / 16-bit 小端 PCM，时长换算 `(字节数 / 2) * 1000 / 16000`
+//! 原本散落在各 ASR provider 里重复（foundry / sherpa / whisper / mimo），这里收口成
+//! 唯一实现，各处改为薄封装调用（参考 `wav::encode_wav_16k_mono` 的共享先例）。
+
+/// 每个采样的字节数（16-bit → 2 字节）。
+const PCM_BYTES_PER_SAMPLE: u64 = 2;
+/// 采样率（16 kHz）。
+const PCM_SAMPLE_RATE_HZ: u64 = 16_000;
+
+/// 由原始字节数计算 16 kHz / 单声道 / 16-bit PCM 的时长（毫秒）。
+pub fn pcm_duration_ms_from_bytes(bytes: u64) -> u64 {
+    (bytes / PCM_BYTES_PER_SAMPLE) * 1000 / PCM_SAMPLE_RATE_HZ
+}
+
+/// 由 PCM 字节切片计算 16 kHz / 单声道 / 16-bit PCM 的时长（毫秒）。
+pub fn pcm_duration_ms(pcm: &[u8]) -> u64 {
+    pcm_duration_ms_from_bytes(pcm.len() as u64)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn one_second_of_16k_i16_pcm_is_1000ms() {
+        // 16000 采样 × 2 字节 = 32000 字节 = 1 秒
+        assert_eq!(pcm_duration_ms(&vec![0u8; 32_000]), 1000);
+        assert_eq!(pcm_duration_ms_from_bytes(32_000), 1000);
+    }
+
+    #[test]
+    fn odd_trailing_byte_is_floored() {
+        // 末尾半个采样向下取整，与历史行为一致
+        assert_eq!(pcm_duration_ms(&vec![0u8; 33]), pcm_duration_ms(&vec![0u8; 32]));
+    }
+}
diff --git a/openless-all/app/src-tauri/src/asr/whisper.rs b/openless-all/app/src-tauri/src/asr/whisper.rs
index 788e5b9a..f5626734 100644
--- a/openless-all/app/src-tauri/src/asr/whisper.rs
+++ b/openless-all/app/src-tauri/src/asr/whisper.rs
@@ -285,7 +285,7 @@ fn extract_confident_text(json: &serde_json::Value) -> String {
 }
 
 fn pcm_duration_ms(pcm: &[u8]) -> u64 {
-    (pcm.len() as u64 / PCM_BYTES_PER_SAMPLE as u64) * 1000 / PCM_SAMPLE_RATE_HZ
+    super::pcm::pcm_duration_ms(pcm)
 }
 
 fn split_pcm_by_duration(pcm: &[u8], max_chunk_duration_ms: Option<u64>) -> Vec<&[u8]> {