Why Video File Size Increases After Trimming and How to Avoid It

“I've got an MP4 video file that's around 1.5GB. I want to trim it down and I don't have a problem using the editing tools to get it to about half its length, but when I go to save the project it ends up being just as large, or larger. How can I just trim it down without increasing its file size?”

There is a common misconception about video trimming: if we cut some parts from a video, we will naturally get a smaller file. But sometimes you may encounter a situation where the video becomes larger after cutting. This is due to the video being transcoded.

Transcoding or re-encoding means that the video is encoded differently. For example, many video editors will use MPEG-4 encoding as the default export option because it has wide compatibility. However, this is a less efficient compression format than H.264 and HEVC, and if you edit an HEVC video in such a video editor and export it as an MPEG-4 file, the file size will usually increase. In addition, most editing programs also use a higher bitrate to make the output quality closer to the original, resulting in a larger output file.

As mentioned before, transcoding is what causes the video size to increase after editing. Therefore, to avoid this, you should not transcode the video.

Most video editors allow you to adjust the output parameters, and you can avoid transcoding by choosing the same settings as the original video parameters when you finish editing. You can find various tutorials online to teach you how to do it. If you want to save some trouble, you can also use the following software to make quick cuts and save space. Let's see more details.

Trim Video without File Size Increasing

WonderFox HD Video Converter Factory Pro is a simple video editing software on Windows that can quickly cut videos without transcoding. Here is a tutorial on how to cut videos using this software. Free download Free download the software and follow the steps.

Step 1. Run the software on your PC and open 'Converter'. Next, drag your video into the workspace.

Step 2. Click the 'Trim' icon (scissors) to open the Trim window. Next, drag the slider to select the part you want to keep, then click 'Trim' to create 'Clip 1'. You can also enter the start time and end time to trim the video more accurately. Repeat this step to create multiple clips. After trimming, click 'OK' to save changes.

Step 3. Open the output format list on the right and select the output format under the "Video" category (it is recommended to keep the same format). Afterwards, the software will smart-fit the output settings to be the same as the input. But if you want to reduce the file size further, you can go into 'Parameter settings' and choose an advanced video encoder or lower the bitrate.

Step 4. Click the ▼ button at the bottom to set an output path or leave it as default.

Step 5. Finally, click 'Run' to finish the process. If the hardware acceleration is enabled, it will boost the conversion speed greatly (up to 30x faster).

Re-encoding is the reason why videos become larger after trimming. To solve this problem, you should avoid re-encoding or keep the same video settings as the original video. With the software introduced here, you can trim videos correctly without increasing the file size. That's all I want to share. I hope this article is helpful to you. Thanks for reading!