Convert AE Time Stretch to Twixtor Speed

Generally speaking there are two ways of defining speed.
100% are always the original speed.
But 50% could either mean that it’s twice as fast, or half as slow. Both have advantages and disadvantages. So you can’t generally say that one is better than the other.

In After Effects you can stretch a layers time like this:

As you can see, a value of 50% stretches the length of the layer to half of it’s original size, which as a result will play it back twice as fast.
In Twixtor the percentage value of the speed works the exact opposite. If you set the speed to 50% it would play back half as fast, in slowmotion.

Let’s say you have a layer with a timestretch of 50%, but you want to try if Twixtor does a better job at it.
The Twixtor speed value would be 200%.
This is simple enough.
But, what if we have a more specific value, like 13,7%? What would then be the equivalent in Twixtor?

This is the mathematical function:


Whereas "x" is either the Twixtor value, or the timestretch value.

Below you can see an example:

100*100/13,7 = 729,927

This is also reversible with the same function!

100*100/729,927 = 13,7

Simple as that 🙂