Pregnancy due date calculator template

Free build guide: Pregnancy due date calculator for WordPress

This guide rebuilds the Pregnancy due date calculator from this site in Gravity Forms: 2 inputs, 4 live results and no submit button. Expect about 18 minutes by hand. The template above is the same form as an import file, and the bundle adds a PDF version of this guide with a screenshot of every setting, plus the stylesheet.

You will end up with:

• Weeks pregnant
• and days
• Days until the due date
• Trimester

What you need

• Gravity Forms (any license) — Calculation fields are in core; datediff(), floor() and the if-block need GP Advanced Calculations.
• GP Advanced Calculations (Gravity Wiz) — Exponents, functions and date maths in calculation fields. The formulas in this template use its syntax. Part of Gravity Perks; needs the Spellbook plugin active as well.

The formulas below use GP Advanced Calculations syntax: exponents, functions or date maths that core calculation fields cannot do. Install and activate it, with its Spellbook parent plugin, before you start; without it every result shows 0.

1. Create the form

1. Go to Forms → New Form and name it Pregnancy due date.
2. In Form Settings → Form Layout, set the CSS Class Name to fo-live-only. Step 3 uses it to hide the submit button.
3. Leave the form open in the editor; the fields come next.

2. Add the fields, in this order

Field IDs are assigned as you add fields. If yours come out differently, change the {Label:ID} references in the formulas to match your IDs. Settings not mentioned stay at their defaults.

1. First day of last period · Date · ID 1
Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed).

2. Cycle length (days) · Number · ID 2
Number Format 9,999.99; Default Value 28; Description “28 is average; the due date shifts a day per day of difference.”; Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed).

3. Weeks pregnant · Number · ID 3
Number Format 9,999.99; Description “Gestational age, counted from the last period.”; Custom CSS Class (Appearance tab) fo-result; tick Enable Calculation, Rounding 0.

floor( ( datediff( {First day of last period:1}, today() ) - ( {Cycle length:2} - 28 ) ) / 7 )

4. and days · Number · ID 4
Number Format 9,999.99; Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed); Custom CSS Class (Appearance tab) fo-result fo-result--sub; tick Enable Calculation, Rounding 0.

( datediff( {First day of last period:1}, today() ) - ( {Cycle length:2} - 28 ) ) % 7

5. Days until the due date · Number · ID 5
Number Format 9,999.99; Description “Due date = last period + 280 days, adjusted for cycle length.”; Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed); Custom CSS Class (Appearance tab) fo-result fo-result--sub; tick Enable Calculation, Rounding 0.

280 - ( datediff( {First day of last period:1}, today() ) - ( {Cycle length:2} - 28 ) )

6. Trimester · Number · ID 6
Number Format 9,999.99; Description “First to week 13, second to week 27, third after.”; Custom CSS Class (Appearance tab) fo-result fo-result--sub; tick Enable Calculation, Rounding 0.

if( ( datediff( {First day of last period:1}, today() ) - ( {Cycle length:2} - 28 ) ) < 91 ):
1
elseif( ( datediff( {First day of last period:1}, today() ) - ( {Cycle length:2} - 28 ) ) < 189 ):
2
else:
3
endif;

3. Hide the submit button

The results are live, so nothing needs submitting. Add this filter to your theme’s functions.php or a code-snippets plugin; it hides the button on any form carrying the fo-live-only class:

add_filter( 'gform_submit_button', function ( $button, $form ) {
	return str_contains( (string) rgar( $form, 'cssClass' ), 'fo-live-only' ) ? '' : $button;
}, 10, 2 );

Or with CSS alone: .fo-live-only_wrapper .gform_footer { display: none; }

4. Put it on a page and make it look like this

Add the form to any page with the Gravity Forms block, or the shortcode [gravityform id="X" title="false" ajax="false"]. The form inherits your theme’s styles; the classes you set in step 2 are hooks for the look you see on this site:

• fo-result on a calculation field makes it the big teal result panel.
• fo-result fo-result--sub makes the smaller secondary figures.
• fo-segmented on a radio field turns it into a segmented switch.
• Two fields on one row is the editor’s own column layout: drag a field beside another and the row splits in half. No CSS class is needed, and the old gf_left_half Ready Classes are deprecated.

The bundle includes the two stylesheets that implement those classes, with notes on matching your brand colours. Without them the form still works; it just looks like your theme’s default Gravity Forms styling.

How the maths works is explained under “How it’s calculated” on the live Pregnancy due date calculator.