I have a fairly large-scale site to build? How many custom fields can I use without running into MySQL database limitations?

  • 1
    How many do you think you'll need? I've got one site where one channel has 58 fields, another channel has 38 then another with 20 plus a few smaller ones with around 5-10 each. No issues whatsoever... yet!
    – foamcow
    Nov 27, 2012 at 11:30
  • I've got about 160 fields planned. It's a migration from another site which had a fairly intense data structure. Will try refine before importing! Nov 27, 2012 at 19:41

4 Answers 4


From the MySQL docs:

"There is a hard limit of 4096 columns per table, but the effective maximum may be less for a given table."

Keep in mind that each field uses two columns, one for field data, another for field type. So divide the maximum column limit by two, and then subtract 3 for the entry_id, site_id, and channel_id columns; which leave you with the possibility of 2046.5 fields.

"Every table (regardless of storage engine) has a maximum row size of 65,535 bytes."

Here are full details: http://dev.mysql.com/doc/refman/5.0/en/column-count-limit.html

  • 1
    It's not quite as simple as that - As I understand it the MySQL limits are affected by the column types/lengths. Eg, if you have lots of custom fields that are dates, these take up more space than an INT(2). Nov 27, 2012 at 19:10
  • All custom fields in EE are stored as TEXT, unless you make changes to the backend database. Nov 28, 2012 at 5:37
  • When you use Matrix, your field's contribution to row_length is greatly reduced.
    – Ian Pitts
    Dec 4, 2012 at 16:55
  • I just added a 10th site to my EE 1.6 MSM and it threw and error saying I had maxed out the number of columns available. It maxed out at the 507th field.
    – Chris
    Feb 27, 2015 at 20:29
  • @Chris How many total columns in the table that is maxed out?
    – Anna_MediaGirl
    Feb 27, 2015 at 20:48

Back in the EE1 days I remember some people hitting the limit at around 750 custom fields - usually caused by ambitious Multi-Site-Manager installations. I think they made some improvements in EE2 that may have pushed that a little higher, but either way unless you're using MSM it shouldn't be a problem even for massive sites.


I have maxed out at between 800-900 custom fields per EE install. This is on EE 1.6.7 and is an MSM installation with about 9 sites so not all of those custom fields are for a single site.


I'm guessing you know this but EE adds a new column for all entries with every new field (exp_channel_data). So if you had many field groups with many fields this table might hit MySQLs limit, but 2046 ((4096 - 3) / 2) fields is quite extreme and I'd say you need to reconsider your site structure if you need this many! The most I've used is a few hundred, including matrix fields, on a very complex site.

MediaGirl and James have posted the answer, but it's something that shouldn't be an issue.

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