diff --git a/starlette/datastructures.py b/starlette/datastructures.py
index 1a8b965e8..3f32a7f23 100644
--- a/starlette/datastructures.py
+++ b/starlette/datastructures.py
@@ -455,11 +455,17 @@ async def read(self, size: int = -1) -> bytes:
             return self.file.read(size)
         return await run_in_threadpool(self.file.read, size)
 
-    async def seek(self, offset: int) -> None:
+    async def seek(self, offset: int, whence: int = 0) -> None:
         if self._in_memory:
-            self.file.seek(offset)
+            self.file.seek(offset, whence)
         else:
-            await run_in_threadpool(self.file.seek, offset)
+            await run_in_threadpool(self.file.seek, offset, whence)
+
+    async def tell(self) -> int:
+        if self._in_memory:
+            return self.file.tell()
+        else:
+            return await run_in_threadpool(self.file.tell)
 
     async def close(self) -> None:
         if self._in_memory:
diff --git a/tests/test_datastructures.py b/tests/test_datastructures.py
index b110aa8bd..fb7549feb 100644
--- a/tests/test_datastructures.py
+++ b/tests/test_datastructures.py
@@ -1,4 +1,5 @@
 import io
+import os
 
 import pytest
 
@@ -220,9 +221,20 @@ class BigUploadFile(UploadFile):
 @pytest.mark.anyio
 async def test_upload_file():
     big_file = BigUploadFile("big-file")
-    await big_file.write(b"big-data" * 512)
     await big_file.write(b"big-data")
+    assert (await big_file.tell()) == 8
     await big_file.seek(0)
+    assert (await big_file.tell()) == 0
+    await big_file.seek(0, os.SEEK_END)
+    assert (await big_file.tell()) == 8
+    await big_file.write(b"big-data" * 511)
+    await big_file.write(b"big-data")
+    pos = await big_file.tell()
+    assert pos > 512 * len(b"big-data")
+    await big_file.seek(-10, os.SEEK_CUR)
+    assert (await big_file.tell()) == pos - 10
+    await big_file.seek(0)
+    assert (await big_file.tell()) == 0
     assert await big_file.read(1024) == b"big-data" * 128
     await big_file.close()