The short answer
Search this question and you get four confident answers: 7 to 15 seconds, under 30 seconds, 30 to 90 seconds, under 3 minutes. Each is presented as the data-backed truth. They cannot all be right, and the reason they disagree is more useful than any of them.
Why every guide gives a different number
Because they are all measuring the same thing indirectly. Completion rate is what the algorithm rewards, and shorter videos are mechanically easier to complete. So any analysis of "what length performs best" finds shorter is better — right up until it finds the shortest videos also say the least, and performance drops again.
The number each guide lands on is really an artefact of whose videos they measured. A dataset of meme accounts gives you 7 seconds. A dataset of educational creators gives you 90. Neither describes your content.
What is actually established
- The first few seconds decide most of it. Mosseri has said repeatedly that a video's fate is largely settled early. That is a hook problem, not a length problem.
- Instagram raised the Reels ceiling substantially, but around 3 minutes remains the practical cutoff for distribution to people who do not follow you. Longer is allowed; it is not equally distributed.
- TikTok now distributes longer videos well — 1 to 3 minutes and beyond — provided completion holds up. This is a genuine reversal of the old "keep it under 15 seconds" advice.
- Completion, rewatches and sends are the measured outcomes. Duration is an input you control; those are the things being scored.
Notice that Instagram and TikTok now point in slightly different directions. Instagram's guidance leans shorter for cold reach; TikTok has been actively rewarding longer. If you post the same clip to both, you are optimising for two different curves — one more reason not to chase a single magic number.
Rules of thumb, clearly labelled as such
If you want starting points rather than laws — these are ours, not platform-stated numbers:
| Goal | Rough range | Why |
|---|---|---|
| Reaching people who do not follow you | Short — under ~30s | Completion is the barrier, and strangers give you the least patience |
| Something for your existing audience | 30s – 2 min | They already opted in; substance beats brevity |
| Teaching something properly | As long as it stays good | A padded 90s video loses to a dense 3-minute one |
| Cross-posting one file everywhere | Under 3 min | Clears YouTube Shorts, the tightest of the major short-form caps |
Hard maximums per platform and format, which genuinely are published, are in the video specs table.
The better question
Instead of "how long should this be", ask "where does this get boring" — then cut there. That is the same instinct the ranking systems are approximating, and unlike a target duration it works on your specific video rather than an average of strangers'.
The related question worth more of your attention is what makes something forwardable, since sends drive reach beyond your followers more than any other signal. That is covered in sends per reach.
Questions people actually ask
How long should an Instagram Reel be?
There is no single optimal length. Instagram rewards completion, rewatches and sends rather than duration, so the practical answer is as long as it stays good. Under about 30 seconds tends to help when reaching people who do not follow you; around 3 minutes is the practical cutoff for non-follower distribution.
Do shorter Reels get more reach?
Shorter videos are easier to finish, and completion is rewarded — so shorter often correlates with better numbers. But cutting a good video down to hit a target length usually removes the substance and hurts sends, which matter more for reaching new people.
Why does every guide give a different optimal length?
Because they are measuring completion indirectly, on different content. A dataset of meme accounts suggests 7 seconds; a dataset of educational creators suggests 90. Neither describes your videos.
Should TikToks be longer than Reels?
They can be. TikTok has been distributing 1–3 minute videos well when completion holds, while Instagram guidance leans shorter for cold reach. If you post one file to both, you are serving two slightly different curves.