diff --git a/src/spikeinterface/core/baserecording.py b/src/spikeinterface/core/baserecording.py
index 0a9b26931b..6328199475 100644
--- a/src/spikeinterface/core/baserecording.py
+++ b/src/spikeinterface/core/baserecording.py
@@ -187,17 +187,24 @@ def add_recording_segment(self, recording_segment: "BaseRecordingSegment") -> No
         """
         super().add_segment(recording_segment)
 
-    def get_sample_size_in_bytes(self):
+    def get_sample_size_in_bytes(self, dtype=None):
         """
         Returns the size of a single sample across all channels in bytes.
 
+        Parameters
+        ----------
+        dtype : data-type, optional
+            The data type to use for calculating the sample size. If None,
+            the recording's dtype is used.
+
         Returns
         -------
         int
             The size of a single sample in bytes
         """
         num_channels = self.get_num_channels()
-        dtype_size_bytes = self.get_dtype().itemsize
+        dtype = self.get_dtype() if dtype is None else np.dtype(dtype)
+        dtype_size_bytes = dtype.itemsize
         sample_size = num_channels * dtype_size_bytes
         return sample_size
 
diff --git a/src/spikeinterface/core/time_series.py b/src/spikeinterface/core/time_series.py
index d4d4717dff..62113dafd2 100644
--- a/src/spikeinterface/core/time_series.py
+++ b/src/spikeinterface/core/time_series.py
@@ -34,7 +34,7 @@ def get_num_samples(self, segment_index: int | None = None) -> int:
         raise NotImplementedError
 
     @abstractmethod
-    def get_sample_size_in_bytes(self) -> int:
+    def get_sample_size_in_bytes(self, dtype=None) -> int:
         raise NotImplementedError
 
     @abstractmethod
diff --git a/src/spikeinterface/core/time_series_tools.py b/src/spikeinterface/core/time_series_tools.py
index fad697f94e..efdedc8282 100644
--- a/src/spikeinterface/core/time_series_tools.py
+++ b/src/spikeinterface/core/time_series_tools.py
@@ -62,9 +62,7 @@ def write_binary(
     if add_file_extension:
         file_path_list = [add_suffix(file_path, ["raw", "bin", "dat"]) for file_path in file_path_list]
 
-    dtype = dtype if dtype is not None else time_series.get_dtype()
-
-    sample_size_bytes = time_series.get_sample_size_in_bytes()
+    sample_size_bytes = time_series.get_sample_size_in_bytes(dtype=dtype)
 
     file_path_dict = {segment_index: file_path for segment_index, file_path in enumerate(file_path_list)}
     if file_timestamps_paths is not None:
@@ -125,7 +123,7 @@ def _write_binary_chunk(segment_index, start_frame, end_frame, worker_ctx):
     byte_offset = worker_ctx["byte_offset"]
     file = worker_ctx["file_dict"][segment_index]
     file_timestamps_dict = worker_ctx["file_timestamps_dict"]
-    sample_size_bytes = time_series.get_sample_size_in_bytes()
+    sample_size_bytes = time_series.get_sample_size_in_bytes(dtype=dtype)
 
     # Calculate byte offsets for the start frames relative to the entire recording
     start_byte = byte_offset + start_frame * sample_size_bytes