# Changing the LENGTH tag doesn't work for me

**URL:** <https://community.mp3tag.de/t/changing-the-length-tag-doesnt-work-for-me/54947>\
**Category:** Support\
**Created:** [October 31, 2021, 1:18am UTC](https://community.mp3tag.de/t/changing-the-length-tag-doesnt-work-for-me/54947 "2021-10-31T01:18:38Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![ryerman](https://community.mp3tag.de/user_avatar/community.mp3tag.de/ryerman/32/5285_2.png) [@ryerman](https://community.mp3tag.de/u/ryerman)\
**Post date:** [October 31, 2021, 3:45am UTC](https://community.mp3tag.de/t/changing-the-length-tag-doesnt-work-for-me/54947/2 "2021-10-31T03:45:56Z")

</div>

> [@JRS001](#):
>
> ... I can type anything in the space for LENGTH in the tag panel and save the file, but when I right click on the file itself in the Windows directory it's in and look at the Properties, it's still exactly the same as it was....

In Mp3tag, LENGTH is an ID3 field.  
Windows File Explorer does not use this to display the length of a MP3 track.  
It is not necessary for a MP3 track to have an ID3 tag.  
The file properties (eg. bitrate, size) are used to calculate the length.  
If you want to populate the LENGTH field shown in your tag panel, use an action like this:  
 ![format Length field](https://community.mp3tag.de/uploads/default/original/2X/4/4fbb67cffd5f0ab7bfc1f3ab5e90fd91d5eabc06.jpeg)

> [@Are "Encoder" Tags really necessary...?](https://community.mp3tag.de/t/are-encoder-tags-really-necessary/54923/5):
>
> You have to differentiate between the ID3 tags and the MP3 info tag. Lame, for example, describes the MP3 info tag as far as I know and stores Econder information there (Lame header). But this is not a tag that you can edit with MP3Tag. Some info tools display this data stored in the file, e.g. B. "Media Info." [https://mediaarea.net/en/MediaInfo](https://mediaarea.net/en/MediaInfo) Mp3Tag shows some of this information if you right-click on a file in MP3Tag and select Properties. In addition, there are ID3V2 tag fields that c…

> [@JRS001](#):
>
> ....combine a lot of separate mp3 files into one, using the Windows command prompt. It works perfectly and the resulting files play fine, but Windows always keeps the tag data from the FIRST file you are combining, so the LENGTH tag is always wrong...

That is not my experience.  
For me, this command produces "newfile.mp3" with an accurate length shown in File Explorer.  
`copy /b file1.mp3 + file2.mp3 newfile.mp3`

---

_[View the full topic](https://community.mp3tag.de/t/changing-the-length-tag-doesnt-work-for-me/54947)._