> ## Documentation Index
> Fetch the complete documentation index at: https://docs.getlago.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Standard

Select the standard charge model if you want to charge the **same price for each
unit** consumed.

Imagine that your API company charges \$0.05 per API call (i.e. your billable
metric). By selecting the standard charge model, you will define a fixed unit
price. If a customer makes 1,000 API calls during the billing period, the total
invoice amount will be \$0.05 x 1,000 API calls = \$50.

<Note>
  Only the `standard` & `dynamic` charge models support the [custom invoice grouping](/guide/invoicing/overview#custom-invoice-grouping).
</Note>