<p>(115bpm / 120 bpm) * 100 = 95.83% (approx, to 2 decimal places)</p>

<p>Speed change percentages are always confusing.</p>

<p><a href="https://support.apple.com/kb/PH12643?locale=en_US&amp;viewlocale=en_US" rel="nofollow noreferrer">Final cut expresses speed changes as</a>:</p>

<blockquote>
  <p>If you change the speed to 50 percent, your clip becomes twice as long
  [...] 
  If you change the speed to 200 percent, the clip becomes half as
  long</p>
</blockquote>

<p>So if you go from 120 bpm to 115 (a slower tempo), you are looking for a longer clip, so your percentage should be lower than 100%.</p>

CC BY-SA 4.0
2019-07-01T08:05:42.007Z
That should be `(115bpm / 120 bpm)`
Gyan
CC BY-SA 4.0
2019-07-01T08:07:41.423Z
gah... told you it was confusing :) thanks
tomh
CC BY-SA 4.0
2019-06-30T20:35:23.693Z
2019-07-01T08:07:28.593Z
2019-07-01T08:07:28.593Z
tomh
<p>scenario:</p>

<p>I have video matched with audio (song).</p>

<p>I slow the audio (song) down (eg from 120 bpm to 115bpm ie, I know exactly how much slower the new audio is than the original video)</p>

<p>How do I calculate how much to slow down my video by (in Final Cut I have the option of slowing down from 100% speed right down to 1%) so it matches the slow(er) audio?</p>

<p>thanks.</p>

<video><video-editor><audio>
Formula / Calculate how much to slow video down to match audio?
T.McL
# Formula / Calculate how much to slow video down to match audio?

(Asked by: username_0 on 2019-06-30)

scenario:

I have video matched with audio (song).

I slow the audio (song) down (eg from 120 bpm to 115bpm ie, I know exactly how much slower the new audio is than the original video)

How do I calculate how much to slow down my video by (in Final Cut I have the option of slowing down from 100% speed right down to 1%) so it matches the slow(er) audio?

thanks.

**Tags:** video, video-editor, audio


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## 1 answers

### Answer by username_1 on 2019-06-30. Score: 0 | Accepted answer

(115bpm / 120 bpm) \* 100 = 95.83% (approx, to 2 decimal places)

Speed change percentages are always confusing.

[Final cut expresses speed changes as](https://support.apple.com/kb/PH12643?locale=en_US&viewlocale=en_US):

> If you change the speed to 50 percent, your clip becomes twice as long
> [...]
> If you change the speed to 200 percent, the clip becomes half as
> long

So if you go from 120 bpm to 115 (a slower tempo), you are looking for a longer clip, so your percentage should be lower than 100%.

> **Comments:**
> **username_2**: That should be `(115bpm / 120 bpm)`  
> **username_1**: gah... told you it was confusing :) thanks  

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