Element count, round up or down?

@coachlizschneider Could you please help clarifying whether to round up or down when calculating number of required items. Here are few examples:

  1. Water closets, say we need 1 per 10 people and we have 44 occupancy (22m/22f) would we have 6 (3m/3f) water closets in all?

  2. Zoning requires one tree every 20 feet, we have 62 feet, do we plant 4 trees or 3?

  3. When occupancy is 49.3, should we think of it as 49 or 50?

Are there any “rules of thumb” for these calculations?


@tatyana.swift Great question. The rule of thumb for these types of code requirements is to round up. You typically want to make sure that you are providing enough plumbing fixtures or egress width for the maximum number of people.

  1. If your occupancy is 44 people and you have to provide 1 water closet for every 10 people you would provide 5 water closets. 4 for the first 40 (40/10 = 4) and 1 for the remaining 4 people.
  2. You would provide 4 trees to make sure you have one every 20 feet.
  3. If you calculate your occupancy at 49.3 you would round up to 50.

This way you are complying with the strictest interpretation of the code.


Great, thank you!

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One quick follow up question in regards to the toilet count. Would this one additional toilet be male or female?

Thank you!

@tatyana.swift Good follow up! For the toilet count you would start by dividing 44 by 2, per 2902.1.1 of the code. So you would have 22 women and 22 men. So using the same rule of 10 water closets per person you would have 3 for the women and 3 for the men. To break that down, that would be 2 for the first 20 (20/10=2) and 1 for the remaining 2 in each case.


Would rounding up be the case if this was for the maximum allowable occupancy for a space?

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Hi @aowen ,

When calculating occupancy you want to round up, as you can’t have a partial occupant and need to err on the side of caution (which means accounting for more people needing to exit the space) when it comes to occupancy.

You can read more about why you round up in this specific situation in the thread below:

Check out some other related ‘round up or down’ threads at the links below:

Hope this helps!