# In a list, should the “off number” be first or second?

I apologize for the ambiguity of the question title.

I have a dropdown list which users must select from. The list goes from 0-55 in increments of 5.

Further information:

• In my specific case, the dropdown represents fuel remaining in an aircraft.
• 0 and 55 are both valid but highly unlikely choices, since these aircraft are almost never completely empty and also almost never full after a flight is completed.
• I don't really care whether the "extra" item occurs at 0 or at 55, I'm only interested in making it simple and usable.
• I have no choice - I must use a dropdown list. I can choose the increments but 5 is "normal" for this specific case.

My choices are:

``````0-5
6-10
11-15
...
51-55
``````

or

``````0-4
5-9
10-14
...
50-55
``````

Which is easier for users?

• i think first one is more common and less confusing. – Stanley VM Sep 25 '15 at 15:04
• From 0 to 55, you have in fact 56 numbers and not 55. Is there a particular reason why you would want one of the bins to be larger in size? – nightning Sep 25 '15 at 16:25
• @nightning - I've added further information to the question to make my specific case (hopefully) more clear. – Steve V. Sep 26 '15 at 1:27

Since 0 is such an unlikely choice, might there any value in having it as a specific value by itself? I don't know about your specific application, but my first impression is that it would be useful to keep track separately of times where the remaining fuel was actually 0. i.e. your dropdown options would be:

`````` 0 (EMPTY)
1 - 5
6 - 10
11 - 15
16 - 20
...
51 - 55
``````

If there's no value in having 0 separate, then I would agree with this:

Typically the most common pattern seems to be: 1-5, 6-10, 11-15, ... , 50-55, etc.

and use the first option from your question (0-5, 6-10, etc) - I don't know that there's necessarily a "correct" option, but this way certainly feels the most natural to me.

• I agree, and I may have an entry for "FULL" as well. We'll leave that up to testing and see how it goes. – Steve V. Sep 29 '15 at 0:26

Typically the most common pattern seems to be: 1-5, 6-10, 11-15, ... , 50-55, etc.

Having 56 items is uneven if your going from 0-55, however you may have meant 55 items, in that case you would be talking of a scale 0-54 (55 items), which would work too. But if you have 0 as the first number displayed I would recommend adding 1 to the result of the number output of it is generated, unless your system depends on, or is designed for, the first entry to start at zero.

• Thanks! I actually did mean 56 items, with a scale of 0-55. I've added more specific information in the question to make it less general. – Steve V. Sep 26 '15 at 1:28