# What are the unites for UniFrac distances

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### Colin Brislawn

Oct 17, 2016, 2:55:22 PM10/17/16
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Good morning,

What are the units associated with the UniFrac distance metric? Is it some measure of branch length, or is a 'percent shared branch length' and thus unit-less?

Colin

### Jamie Morton

Oct 17, 2016, 5:55:52 PM10/17/16
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Hi Colin,

That's actually a very interesting question.  I wouldn't think it is unitless, since it is proportional to the shared branch length.

I've forwarded this to one of the developers of Unifrac, so expect to hear a confirmation soon.

Cheers,
Jamie

### Colin Brislawn

Oct 20, 2016, 1:30:19 PM10/20/16
Feedback from Tony:
It doesn't have units - it's a proportion of the overall branch length.

So while the branch length may have units, the units cancel when calculating the proportion of branch length shared, and thus the metric is unitless.

Thanks!
Colin

PS. Out of curiosity, what are the units for branch length?