diff --git a/docs/requests.md b/docs/requests.md
index 747e496d1..11fb58343 100644
--- a/docs/requests.md
+++ b/docs/requests.md
@@ -123,6 +123,7 @@ multidict, containing both file uploads and text input. File upload items are re
 * `content_type`: A `str` with the content type (MIME type / media type) (e.g. `image/jpeg`).
 * `file`: A <a href="https://docs.python.org/3/library/tempfile.html#tempfile.SpooledTemporaryFile" target="_blank">`SpooledTemporaryFile`</a> (a <a href="https://docs.python.org/3/glossary.html#term-file-like-object" target="_blank">file-like</a> object). This is the actual Python file that you can pass directly to other functions or libraries that expect a "file-like" object.
 * `headers`: A `Headers` object. Often this will only be the `Content-Type` header, but if additional headers were included in the multipart field they will be included here. Note that these headers have no relationship with the headers in `Request.headers`.
+* `size`: An `int` with file's size in bytes.
 
 `UploadFile` has the following `async` methods. They all call the corresponding file methods underneath (using the internal `SpooledTemporaryFile`).
 
diff --git a/starlette/datastructures.py b/starlette/datastructures.py
index eee3834e0..00c9810e4 100644
--- a/starlette/datastructures.py
+++ b/starlette/datastructures.py
@@ -430,12 +430,14 @@ class UploadFile:
     def __init__(
         self,
         file: typing.BinaryIO,
+        size: int,
         *,
         filename: typing.Optional[str] = None,
         headers: "typing.Optional[Headers]" = None,
     ) -> None:
         self.filename = filename
         self.file = file
+        self.size = size
         self.headers = headers or Headers()
 
     @property
@@ -449,6 +451,8 @@ def _in_memory(self) -> bool:
         return not rolled_to_disk
 
     async def write(self, data: bytes) -> None:
+        self.size += len(data)
+
         if self._in_memory:
             self.file.write(data)
         else:
diff --git a/tests/test_datastructures.py b/tests/test_datastructures.py
index 16f9da4a5..0271cfd08 100644
--- a/tests/test_datastructures.py
+++ b/tests/test_datastructures.py
@@ -275,10 +275,12 @@ def test_queryparams():
 async def test_upload_file_file_input():
     """Test passing file/stream into the UploadFile constructor"""
     stream = io.BytesIO(b"data")
-    file = UploadFile(filename="file", file=stream)
+    file = UploadFile(filename="file", file=stream, size=len(stream))
+    assert file.size == 4
     assert await file.read() == b"data"
     await file.write(b" and more data!")
     assert await file.read() == b""
+    assert file.size == 19
     await file.seek(0)
     assert await file.read() == b"data and more data!"
 
@@ -292,7 +294,7 @@ async def test_uploadfile_rolling(max_size: int) -> None:
     stream: BinaryIO = SpooledTemporaryFile(  # type: ignore[assignment]
         max_size=max_size
     )
-    file = UploadFile(filename="file", file=stream)
+    file = UploadFile(filename="file", file=stream, size=len(stream))
     assert await file.read() == b""
     await file.write(b"data")
     assert await file.read() == b""
@@ -307,7 +309,7 @@ async def test_uploadfile_rolling(max_size: int) -> None:
 
 def test_formdata():
     stream = io.BytesIO(b"data")
-    upload = UploadFile(filename="file", file=stream)
+    upload = UploadFile(filename="file", file=stream, size=len(stream))
     form = FormData([("a", "123"), ("a", "456"), ("b", upload)])
     assert "a" in form
     assert "A" not in form