YouTube ShortsAI video editingvideo clippingcontent repurposing

How to Create YouTube Shorts from Existing Video

Learn how to turn your existing videos into YouTube Shorts using AI. A step-by-step guide for creators — no editing experience needed.

Powercut Team··8 min read

Quick Answer

To create YouTube Shorts from existing video: upload your video to an AI clipping tool like Powercut, let the AI find the best moments automatically, review the generated clips, edit trim points and captions, export at 9:16 vertical, and upload to YouTube as a Short.

TL;DR

Upload your existing video to an AI clipping tool like Powercut. The AI scans the footage and surfaces the strongest moments automatically. Review the generated clips, edit trim points and captions as needed, export at 9:16 vertical, and upload directly to YouTube as a Short. The whole process takes about 15 minutes.

Why Your Existing Videos Are a Goldmine for Shorts

Most creators already have everything they need. Old YouTube uploads, recorded webinars, client interviews, tutorial walkthroughs, past livestreams — the shareable moments are buried inside content you have already made.

You do not need to film anything new.

YouTube Shorts is the fastest-growing surface on YouTube. It reaches viewers who would never find your long-form content through search. Repurposing existing video is the easiest way to start posting Shorts consistently — and to get that reach without adding anything to your production schedule.

The problem is extraction. Watching a 60-minute video to find three good clips, cutting each one, reformatting to vertical, adding captions — that is a full day of work. Most creators skip it. The content sits unused.

AI clipping tools like Powercut remove that friction. Upload once, and the AI does the heavy lifting.

How to Create YouTube Shorts from Existing Video: Step-by-Step

This guide follows the actual workflow inside Powercut, step by step.

Step 1: Upload Your Existing Video

Go to the Upload Video page in your Powercut dashboard.

Drag your video file into the upload area, or click to browse. This is where you bring in videos you already have — old YouTube uploads, recorded Zoom calls, webinars, podcast recordings, screen captures. Powercut accepts MP4, MOV, MKV, and WebM — up to 2 GB. That covers most formats you are likely working with.

Use the Max Clips slider to choose how many clips you want generated. For a 30-60 minute video, 5 to 7 clips is a good starting point. You can always delete clips you do not like, so do not overthink the number.

Click Upload and Process when you are ready.

Step 2: Powercut Finds the Best Moments

Once uploaded, Powercut gets to work. You will see a live progress screen while it processes your video.

The AI watches your content, understands what is being said, and identifies the moments most likely to perform — strong takes, clear insights, memorable quotes, high-energy exchanges. You do not need to do anything. Most videos are ready in 3 to 6 minutes.

Step 3: Review Your Clips in My Videos

When processing finishes, Powercut takes you to My Videos.

Your video appears in the list with a Completed badge. Click the arrow next to it to expand and see every clip that was generated. For each clip you can:

You can search and sort your entire library here, and upload more videos at any time.

Step 4: Edit Your Clips for YouTube Shorts

Click the edit icon on any clip to open it in the Clip Editor. This is where you fine-tune for Shorts specifically.

Trim the Start and End

The timeline at the bottom shows a visual strip of the clip. Drag the left handle to move the start point. Drag the right handle to move the end point. The video preview updates as you drag, so you can see exactly what you are keeping.

Use the Previous Frame and Next Frame buttons for frame-accurate precision. For Shorts, keep the final clip under 60 seconds — the 45–55 second range performs best.

Cut Filler Words via Transcript

The panel on the right shows a word-by-word transcript of your clip, synced to the video.

Click any word to jump to that point in the video. To remove a section — a filler word, an awkward pause, a false start — click and drag to select those words, then press Delete. The selected words are struck through and will be removed from the exported clip.

Hit Undo or Redo in the top bar if you change your mind.

Add Captions

Click Captions in the left sidebar. Powercut automatically generates captions from your video.

Pick a caption style — from a simple subtitle bar to bold animated styles where each word highlights as it is spoken. You can also adjust the font size and position. The video preview shows exactly how it will look.

Choose Your Aspect Ratio

Click the aspect ratio selector above the video preview to choose your output format:

For YouTube Shorts, always select 9:16 Vertical. YouTube automatically treats vertical videos under 60 seconds as Shorts. Any other aspect ratio will not appear in the Shorts feed.

Step 5: Save and Download

When your edits look right, click Save Changes in the top bar. Powercut re-renders the clip with your trim, cuts, captions, and aspect ratio applied.

Then click Download to save the MP4 file to your device.

Step 6: Upload to YouTube as a Short

Open YouTube Studio and click Create → Upload Video.

Upload the MP4 you just downloaded. Then:

  1. Add a title — include relevant keywords. Keep it short and direct.
  2. Write a description — add context and relevant hashtags. Include #Shorts so the algorithm flags it correctly.
  3. Set visibility — Public, Unlisted, or Scheduled.
  4. Publish.

YouTube automatically treats vertical videos under 60 seconds as Shorts — they appear in the Shorts feed and on your channel's Shorts tab. No special toggle required.

You can also cross-post the same file to TikTok via the Creator Portal and to Instagram Reels via the app or Meta Business Suite. One export. Three platforms.

What Makes a Good YouTube Short from Existing Content

Match Clip Length to the Platform

Keep It Under 60 Seconds

YouTube Shorts must be under 60 seconds to qualify for the Shorts feed. The 45–55 second range tends to perform best for completion rate. Viewers who finish the clip signal quality to the algorithm.

Hook in the First 2 Seconds

The first 2 seconds decide whether someone keeps watching or scrolls past. Open on the strong take or surprising moment — not the setup that leads up to it. In Powercut's editor, drag the left trim handle to cut any lead-in and open directly on the moment.

Always Add Captions

Most viewers scroll with sound off. Captions keep them watching even without audio — and that directly improves reach and completion rate. Use animated word-highlight captions for best results.

Export at 9:16 (1080x1920)

This is the required format for YouTube Shorts. Keep text and faces in the centre 80% of the frame — platform UI overlays cover the top and bottom edges and can obscure anything placed too close to the edges.

Make It Self-Contained

A clip that relies on context from earlier in the original video will confuse Shorts viewers — they have no idea what came before. Trim to a standalone statement, or add a short title card at the start to give viewers the context they need.

Manual Editing vs. Using an AI Clipping Tool

Cutting Shorts by hand in Premiere Pro or Final Cut takes roughly 4 to 8 hours for a 60-minute source video, because you watch the full video, cut each clip, reframe to vertical, and caption everything separately. An AI clipping tool collapses that to about 15 minutes by doing the first pass for you.

For the full side-by-side breakdown of when each approach is worth it, see How to Make Clips from a Video.

Tools for Creating YouTube Shorts from Existing Video

Powercut is built for this workflow — AI clip detection, trim editor, auto-captions, and 9:16 export in one place. It accepts MP4, MOV, MKV, and WebM up to 2 GB, and is free to try at powercut.ai/upload.

Opus Clip, Descript, and CapCut also handle parts of this job with different tradeoffs. For the full tool-by-tool comparison, see How to Use an AI Video Editor and Opus Clip Alternatives Compared.

Common Mistakes to Avoid

These are the mistakes specific to YouTube Shorts. For the mistakes that apply to repurposing on every platform, see How to Repurpose Video Content for Social Media.

Exporting in landscape. A 16:9 clip will not appear in the Shorts feed at all. This is the single most common reason a repurposed clip fails to get Shorts distribution. Always switch to 9:16 before exporting.

Going over 60 seconds. A 61-second video is not a Short. YouTube will publish it as a regular upload, and it will never enter the Shorts feed. Check the duration before every export.

Placing captions too close to the edges. YouTube's Shorts UI — title, channel name, action buttons — overlays the bottom and right of the frame. Captions positioned there get covered. Keep them in the centre 80%.

Related Resources

Frequently Asked Questions

Can I turn an existing YouTube video into Shorts?
Yes. Download your video from YouTube Studio, upload it to Powercut, and the AI will find the best moments to turn into Shorts.
What is the best length for YouTube Shorts?
Under 60 seconds to qualify as a Short. The 45-55 second range tends to perform best for completion rate.
Do I need to re-film content for YouTube Shorts?
No. Existing videos — tutorials, podcasts, interviews, webinars, livestreams — are some of the best sources for Shorts.
Do YouTube Shorts need captions?
Strongly recommended. Most people scroll with sound off. Captions keep viewers watching and improve reach.
What aspect ratio do YouTube Shorts need?
9:16 vertical (1080x1920). YouTube automatically treats vertical videos under 60 seconds as Shorts.
Can I use the same Short on TikTok and Instagram Reels?
Yes. Export once at 9:16 and upload to all three platforms. Optimal clip lengths vary slightly (TikTok favors 21-34 seconds, Reels favors 15-30 seconds), but a 45-55 second clip works well across all three.
How long does AI processing take?
Typically 3-6 minutes for a 60-minute video.
Can I edit the clips before downloading?
Yes. Every clip opens in a built-in editor with a trim timeline, word-level transcript editing, caption style selection, and aspect ratio controls.
Can I make shorts from a podcast?
Yes — and podcasts are actually one of the best sources. There is already a lot of strong, quotable content buried inside a long episode. Powercut surfaces those moments without you having to watch the whole thing.
Which AI tool is best for converting long videos to shorts?
Powercut is built specifically for this. You upload a video, it finds the highlights, and you get editable clips with captions ready to post — all in one place.
What video formats does Powercut accept?
MP4, MOV, MKV, and WebM files up to 2 GB. That covers recordings from cameras, Zoom, screen recorders, and most other sources.