GetFileSize function (fileapi.h)

Retrieves the size of the specified file, in bytes.

It is recommended that you use GetFileSizeEx.


DWORD GetFileSize(
  [in]            HANDLE  hFile,
  [out, optional] LPDWORD lpFileSizeHigh


[in] hFile

A handle to the file.

[out, optional] lpFileSizeHigh

A pointer to the variable where the high-order doubleword of the file size is returned. This parameter can be NULL if the application does not require the high-order doubleword.

Return value

If the function succeeds, the return value is the low-order doubleword of the file size, and, if lpFileSizeHigh is non-NULL, the function puts the high-order doubleword of the file size into the variable pointed to by that parameter.

If the function fails and lpFileSizeHigh is NULL, the return value is INVALID_FILE_SIZE. To get extended error information, call GetLastError. When lpFileSizeHigh is NULL, the results returned for large files are ambiguous, and you will not be able to determine the actual size of the file. It is recommended that you use GetFileSizeEx instead.

If the function fails and lpFileSizeHigh is non-NULL, the return value is INVALID_FILE_SIZE and GetLastError will return a value other than NO_ERROR.


You cannot use the GetFileSize function with a handle of a nonseeking device such as a pipe or a communications device. To determine the file type for hFile, use the GetFileType function.

The GetFileSize function retrieves the uncompressed size of a file. Use the GetCompressedFileSize function to obtain the compressed size of a file.

Note that if the return value is INVALID_FILE_SIZE (0xffffffff), an application must call GetLastError to determine whether the function has succeeded or failed. The reason the function may appear to fail when it has not is that lpFileSizeHigh could be non-NULL or the file size could be 0xffffffff. In this case, GetLastError will return NO_ERROR (0) upon success. Because of this behavior, it is recommended that you use GetFileSizeEx instead.

Transacted Operations:  If there is a transaction bound to the file handle, then the function returns information for the isolated file view.

In Windows 8 and Windows Server 2012, this function is supported by the following technologies.

Technology Supported
Server Message Block (SMB) 3.0 protocol Yes
SMB 3.0 Transparent Failover (TFO) Yes
SMB 3.0 with Scale-out File Shares (SO) Yes
Cluster Shared Volume File System (CsvFS) Yes
Resilient File System (ReFS) Yes


For an example, see Creating a View Within a File.


Requirement Value
Minimum supported client Windows XP [desktop apps only]
Minimum supported server Windows Server 2003 [desktop apps only]
Target Platform Windows
Header fileapi.h (include Windows.h)
Library Kernel32.lib
DLL Kernel32.dll

See also

File Management Functions