Rails 3. How to explicitly round a number to two decimal places in the model?

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> [Rails 3. How do display two decimal places in edit form?](

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I know I can use sprintf to limit to two decimal places.

When I redisplay the prices in a form or just in a table, sometimes I get 80, instead of 80.00. Wouldn't be better to just store the price with the two decimal places from the very moment the price is entered in the database? That way, whenever it's displayed, it will ALWAYS show the two decimal places. If so, how?

You should try using the `:decimal` type of database field, with the `:scale` set to `2`

To add a decimal column to a new table;

create_table :my_table do |t|
t.decimal :my_column, :scale => 2
end

To add a column to an existing table;

add_column :my_table, :my_column, :decimal, :scale => 2

It is wise to have precisions since some database does not have precision defaults. Such as postgresql:

add_column :my_table, my_column, precision: 30, scale: 2

For this I use the **number_to_currency** formater. Since I am in the US the defaults work fine for me.

<% price = 45.9999 %>
<price><%= number_to_currency(price)%></price>
=> <price>$45.99</price>

You can also pass in options if the defaults don't work for you.
Documentation on available options at [api.rubyonrails.org][1]


[1]:

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If it's a `:float` or `:decimal`, `80` and `80.00` in Ruby are going to be the same thing (as will `80.0000`). The latter isn't "stored" with more decimal places, and trailing zeroes only make sense in the view. You can use `sprintf` like you said, or you can use Rails' handy `number_with_precision` helper:

<%= number_with_precision price, :precision => 2 %>

Here's [another SO question](

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) on this topic, by the way. @Matthew Rudy is right about one thing: For money columns you should be using `:decimal`.

If you're *really* committed to not having this in your view, you could use something like [Draper](

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) to apply decorators to your attributes (which will merely move your `number_with_precision` call out of the way and into a new Decorator class), but it's probably overkill in this instance.

You can simply use `x.round(2)` when displaying the number - that will always display two decimal places. It's generally recommended to store prices as integers in the backend database because they are handled better when you need a really high level of precision. In this case though, you can choose to go either way.