# Calculate Age in ODK

Hi again,

I use ODK and a I have a field date with the birthdate, and the ideai is a calculate the age, I use this formula:

• format-date(today(), ‘%Y’) - format-date(\${Birthdate}, ‘%Y’)

And it work, but I need to use all the date, I mean calculate the age with the year, the month and the day.

Can someone help me, please.

Use this calculation to get the age - `int((today()-\${birthdate}) div 365.25,0)`

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Thanks @ARIF_AZAD_KHAN, it work !!! I really apresiate your help.

on which field does the formula place? Could you give an example? I'm a rookie and I'm about the build.odk

will it run on the xls form

It is possible to add calculations in ODK Build, it's in the Advanced options.

But I think it is easier to use XLSForm. The docs have an example of a `calculate` type question.

hi @danbjoseph think this is better. Thanks for the help, I hope someone serves my tip.

edad.xlsx (9.0 KB)

Here is a working XLSForm example: example_edad.xlsx (9.0 KB)
You can test it at https://opendatakit.org/xlsform/

`survey` worksheet of attached exampe:

``````+-----------+------------------+---------------------+----------+---------------------------------------------------+
|   type    |       name       |        label        | required |                    calculation                    |
+-----------+------------------+---------------------+----------+---------------------------------------------------+
| date      | fecha_nacimiento | Fecha de Nacimiento | true     |                                                   |
| calculate | edad             |                     |          | int((today()-\${fecha_nacimiento}) div 365.25,0)   |
| note      | show_age         | Edad: \${edad}       |          |                                                   |
+-----------+------------------+---------------------+----------+---------------------------------------------------+
``````

in Enketo:

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minor point, but strictly speaking you probably want int(...) not round(...) if you are trying to determine age, in years... [unless of course yer a 20-year old trying to order a drink at the bar in the US... ]

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thank you. good catch. i've edited my post (and the original answer as well) to reflect that (in case someone doesn't read the full thread).

Thanks, this is great!

Please note there may be some times when the above calculation doesn't work.
See this post:

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