# Debular trim length
**URL:** https://forum.qiime2.org/t/debular-trim-length/20735
**Category:** User Support
**Tags:** trim, deblur
**Created:** [September 14, 2021, 7:27am UTC](https://forum.qiime2.org/t/debular-trim-length/20735 "2021-09-14T07:27:17Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Hasinika](https://forum.qiime2.org/u/Hasinika)
#### Post date: [September 14, 2021, 7:27am UTC](https://forum.qiime2.org/t/debular-trim-length/20735/1 "2021-09-14T07:27:17Z")
Hi,
I am new to using Debular for denoising and confused about how to determine the --p-trim-length
According to the Moving Pictures tutorial, the length seems to be based on the quality score, it reads "In general, the Deblur developers recommend setting this value to a length where the median quality score begins to drop too low. On these data, the quality plots (prior to quality filtering) suggest a reasonable choice is in the 115 to 130 sequence position range."
I am working with demultiplexed paired-end sequence data (2x250 bp, all reads are 250 bp, not a meta analysis), the forward read is of good quality, whilst the quality of the reverse drops at around 140. In this case, how do I set the trim length?
Thanks for any help in advance.
Cheers
Hasinika
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### Author:  [@thermokarst](https://forum.qiime2.org/u/thermokarst)
#### Post date: [September 16, 2021, 2:33pm UTC](https://forum.qiime2.org/t/debular-trim-length/20735/2 "2021-09-16T14:33:54Z")
That sounds like a good start, @Hasinika. How about you try to experiment with a few different settings to try to understand what the impact is on the resulting data? That's a great way to get familiar with things. Keep us posted! :qiime2:
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### Author:  [@Hasinika](https://forum.qiime2.org/u/Hasinika)
#### Post date: [September 16, 2021, 7:05pm UTC](https://forum.qiime2.org/t/debular-trim-length/20735/3 "2021-09-16T19:05:15Z")
Thanks for the reply @thermokarst Sorry if I was not clear, my question was do I set the trim length based on just the reverse read? and trim both the forward and reverse reads at ~140 in this case?
Thank you.
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### Author:  [@thermokarst](https://forum.qiime2.org/u/thermokarst)
#### Post date: [September 16, 2021, 7:59pm UTC](https://forum.qiime2.org/t/debular-trim-length/20735/4 "2021-09-16T19:59:20Z")
Hi @Hasinika - that's up to you, I encourage you to try it a few different ways and let us know how it goes.
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### Author:  [@system](https://forum.qiime2.org/u/system)
#### Post date: [October 18, 2021, 2:00am UTC](https://forum.qiime2.org/t/debular-trim-length/20735/5 "2021-10-18T02:00:14Z")
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