# Setting the Calculation Weight

Last updated on 10/19/17A calculation weight must be set for every item in a calculation relationship. A calculation weight is a calculation relationship attribute (**-** or **+**) used in building the summation of a calculation relationship. This article describes how to use the balance type (debit or credit) to determine calculation weight and where to set it in Wdesk.

## Determining Calculation Weight

In XBRL, a calculation relationship contributor has either a positive or negative contribution to the calculation relationship total. This is captured in the calculation weight.

The following image shows a portion of an XBRL calculation relationship, as displayed in the XBRL outline.

The calculation relationship contributors preceded by a plus sign have a positive calculation weight, or a positive contribution to the calculation relationship total.

The calculation relationship contributor preceded by a minus sign has a negative calculation weight, or negative contribution to the calculation relationship total.

You can identify the correct calculation weight by understanding and using the balance type defined for the calculation relationship total and for each calculation relationship contributor.

In the next image, a calculation relationship is defined in which the calculation relationship total and all contributors are of balance type debit. The balance type debit is indicated by the **(D)** that precedes each concept.

The calculation weight is positive because each contributor has the same balance type as the calculation relationship total.

## Rules for Determining the Calculation Weight

Wdesk automatically sets calculation weights based on the following rules:

Use a positive calculation weight if the calculation relationship contributors and total share the same balance type.

Use a negative calculation weight if the calculation relationship contributors and total have opposite balance types.

## Setting or Changing the Calculation Weight

If the calculation relationship contributor or the calculation relationship total (or both) lacks a balance type, Wdesk cannot automatically determine the correct calculation weight.

In this case, a drop-down menu appears next to the concept in the **Calculation Assertions** field, as shown in the following image for **Earnings Per Share, Diluted**.

When the drop-down menu appears, select the weight manually based on whether the contribution is negative or positive to the calculation relationship total.

**NOTE:** When you edit a calculation relationship, make sure the calculation weight is still correct.