diff --git a/hca/dss/upload_to_cloud.py b/hca/dss/upload_to_cloud.py
index 3f1237ca..9bc5b99f 100755
--- a/hca/dss/upload_to_cloud.py
+++ b/hca/dss/upload_to_cloud.py
@@ -11,7 +11,8 @@
 import boto3
 from boto3.s3.transfer import TransferConfig
 
-from dcplib.checksumming_io import ChecksummingBufferedReader, S3Etag
+from dcplib import s3_multipart
+from dcplib.checksumming_io import ChecksummingBufferedReader
 
 
 def encode_tags(tags):
@@ -27,7 +28,7 @@ def _mime_type(filename):
     return "application/octet-stream"
 
 
-def _copy_from_s3(path, s3, tx_cfg):
+def _copy_from_s3(path, s3):
     bucket_end = path.find("/", 5)
     bucket_name = path[5: bucket_end]
     dir_path = path[bucket_end + 1:]
@@ -59,19 +60,20 @@ def upload_to_cloud(file_handles, staging_bucket, replica, from_cloud=False):
     :param replica: The cloud replica to write to. One of 'aws', 'gc', or 'azure'. No functionality now.
     :return: a list of each file's unique key name.
     """
-    tx_cfg = TransferConfig(multipart_threshold=S3Etag.etag_stride,
-                            multipart_chunksize=S3Etag.etag_stride)
     s3 = boto3.resource("s3")
     file_uuids = []
     key_names = []
 
     if from_cloud:
-        file_uuids, key_names = _copy_from_s3(file_handles[0], s3, tx_cfg)
-
+        file_uuids, key_names = _copy_from_s3(file_handles[0], s3)
     else:
         destination_bucket = s3.Bucket(staging_bucket)
         for raw_fh in file_handles:
-            with ChecksummingBufferedReader(raw_fh) as fh:
+            file_size = os.path.getsize(raw_fh.name)
+            multipart_chunksize = s3_multipart.get_s3_multipart_chunk_size(file_size)
+            tx_cfg = TransferConfig(multipart_threshold=s3_multipart.MULTIPART_THRESHOLD,
+                                    multipart_chunksize=multipart_chunksize)
+            with ChecksummingBufferedReader(raw_fh, multipart_chunksize) as fh:
                 file_uuid = str(uuid.uuid4())
                 key_name = "{}/{}".format(file_uuid, os.path.basename(fh.raw.name))
                 destination_bucket.upload_fileobj(
@@ -89,11 +91,9 @@ def upload_to_cloud(file_handles, staging_bucket, replica, from_cloud=False):
                     "hca-dss-sha256": sums["sha256"],
                     "hca-dss-crc32c": sums["crc32c"],
                 }
-
                 s3.meta.client.put_object_tagging(Bucket=destination_bucket.name,
                                                   Key=key_name,
-                                                  Tagging=dict(TagSet=encode_tags(metadata))
-                                                  )
+                                                  Tagging=dict(TagSet=encode_tags(metadata)))
                 file_uuids.append(file_uuid)
                 key_names.append(key_name)
 
diff --git a/hca/upload/s3_agent.py b/hca/upload/s3_agent.py
index 132b1443..0109bcec 100644
--- a/hca/upload/s3_agent.py
+++ b/hca/upload/s3_agent.py
@@ -7,8 +7,7 @@
 from botocore.credentials import CredentialResolver
 from botocore.session import get_session
 
-KB = 1024
-MB = KB * KB
+from dcplib import s3_multipart
 
 
 def sizeof_fmt(num, suffix='B'):
@@ -48,7 +47,7 @@ def upload_progress_callback(self, bytes_transferred):
         sys.stdout.flush()
 
     def upload_file(self, local_path, target_bucket, target_key, content_type, report_progress=False):
-        self.file_size = os.stat(local_path).st_size
+        self.file_size = os.path.getsize(local_path)
         bucket = self.s3.Bucket(target_bucket)
         obj = bucket.Object(target_key)
         upload_fileobj_args = {
@@ -69,16 +68,5 @@ def list_bucket_by_page(self, bucket_name, key_prefix):
 
     @classmethod
     def transfer_config(cls, file_size):
-        etag_stride = cls._s3_chunk_size(file_size)
-        return TransferConfig(multipart_threshold=etag_stride,
-                              multipart_chunksize=etag_stride)
-
-    @staticmethod
-    def _s3_chunk_size(file_size):
-        if file_size <= 10000 * 64 * MB:
-            return 64 * MB
-        else:
-            div = file_size // 10000
-            if div * 10000 < file_size:
-                div += 1
-            return ((div + (MB - 1)) // MB) * MB
+        return TransferConfig(multipart_threshold=s3_multipart.MULTIPART_THRESHOLD,
+                              multipart_chunksize=s3_multipart.get_s3_multipart_chunk_size(file_size))
diff --git a/requirements.txt b/requirements.txt
index 4e69d821..b2890630 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -8,6 +8,6 @@ jsonschema >= 2.6, < 3
 requests >= 2.17, < 3
 six >= 1.10, < 2
 tweak >= 0.6.7, < 1
-dcplib >= 1.1.0, < 2
+dcplib >= 1.3.2, < 2
 argcomplete >= 1.9.3, < 2
 commonmark >= 0.7.4, < 1