From this tutorial, you will get knowledge of how to work with **Hidden** and **Calculated** field types to create math formulas in order your visitors could use Forms on the frontend.

### Hidden and Calculated field types

Let’s clear up what **Hidden field** type means, however, the name speaks for itself. In this field, you may add information which won’t be visible on the frontend, but the data you specified will be used in math formula for calculations.

Consequently, let’s see what **Calculated field** type means. With the help of this field type, you can make any calculations using math formulas based on macros and display the result on the frontend. Here, you have an option to use data from either meta fields created previously for your custom posts, or from **Form** fields you created.

### Using Hidden and Calculated field types

Let’s consider an example of using these fields. We’ll create a short **Form** for a product purchase.

**Step 1** – Beforehand we created fields to display product’s **Price**:

and **Quantity**:

**Step 2** – Now, let’s create **Hidden** field type. In this tutorial, we’ll create a field for Tax, which further will be added to the final price, so that on the frontend visitors won’t see **Tax** field separately, but its value will be considered in the formula calculating **Total Price**.

Create a new field and select **Hidden** from the dropdown list in the **Type**:

and input **Name** value:

**Step 3** – Next, in the** Field Value** select **Current Post Meta** and input meta field name ID:

This value stands for pulling data from your **Custom Post Type** meta field. Let’s see where it can be located:

**Step 4** – Now, let’s create a **Calculated** field type and see how **Hidden** field type can be used there. We assume this field’s purpose is to calculate the total price of the product, including tax. Create a new field and select its type as **Calculated** and input a name for it.

**Step 5** – In the **Calculation Formula** field, you need to input a math formula, which will further calculate the product’s total price depending on the quantity a visitor selects. Plus, we need it to consider tax and summarize the final price accordingly.

In this particular case for our tutorial, our **Calculation Formula** consists of **Product Quantit**y multiplied by the **Product Price** plus **Tax**:

**%FIELD::Quantity%*%FIELD::Price%+%FIELD::Tax%**

where **%FIELD::Tax%** is a **Hidden** field type.

**Step 6** – Add **Calculated Value Prefix**, which will be displayed on the frontend and click **Apply Changes** button:

**Step 7** – When your **Form** is ready, click **Publish** button:

**Step 8** – Let’s see how it works on the frontend:

where **Price** and **Quantity** are visible, and **Tax** field is not, however, in the Total calculation formula its value is considered.

If we describe as a math formula: 20 (Price) * 1 (Quantity) + 5 (Tax (hidden field)) = 25

If a visitor changes **Quantity**, the formula still calculates the **Total Price** considering tax value:

That’s all! Now you know how to use **Hidden** and **Calculated** field types to create formulas based on the values from the form fields. Hoping, you’ll enjoy managing your forms and create them effortlessly!