AC / BTU sizing calculator template

Free build guide: AC / BTU sizing calculator for WordPress

This guide rebuilds the AC / BTU sizing calculator from this site in Gravity Forms: 6 inputs, 3 live results and no submit button. Expect about 27 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:

• BTU per hour
• Tons of cooling
• Room area (sq ft)

What you need

• Gravity Forms (any license) — Calculation fields, radio values and drop-down values are in core.

Everything here is core Gravity Forms. No add-ons.

1. Create the form

1. Go to Forms → New Form and name it AC / BTU sizing.
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. Room length (ft) · Number · ID 1
Number Format 9,999.99; Default Value 15; Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed).

2. Room width (ft) · Number · ID 2
Number Format 9,999.99; Default Value 12; Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed).

3. Ceiling height (ft) · Number · ID 3
Number Format 9,999.99; Default Value 8; Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed).

4. People usually in the room · Drop Down · ID 5
Layout: half width, on the same row as its neighbour (drag the field beside it in the editor; no CSS class needed).

Choices (tick show values and enter each value):

• 1 or 2 — value 0 (selected by default)
• 3 — value 600
• 4 — value 1200
• 5 — value 1800
• 6 or more — value 2400

5. Sunlight · Radio Buttons · ID 4
Custom CSS Class (Appearance tab) fo-segmented.

Choices (tick show values and enter each value):

• Shaded — value 0.9
• Average — value 1 (selected by default)
• Very sunny — value 1.1

6. Is it a kitchen? · Radio Buttons · ID 6
Custom CSS Class (Appearance tab) fo-segmented.

Choices (tick show values and enter each value):

• No — value 0 (selected by default)
• Yes — value 4000

7. BTU per hour · Number · ID 7
Number Format 9,999.99; Description “Pick the next unit size up. Window units run 5,000–25,000 BTU.”; Custom CSS Class (Appearance tab) fo-result; tick Enable Calculation, Rounding 0.

( ( {Length:1} * {Width:2} ) * 20 * {Height:3} / 8 * {Sun:4} + {People:5} + {Kitchen:6} )

8. Tons of cooling · Number · ID 8
Number Format 9,999.99; Description “Central and mini-split systems are sized in tons.”; 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 2.

( ( {Length:1} * {Width:2} ) * 20 * {Height:3} / 8 * {Sun:4} + {People:5} + {Kitchen:6} ) / 12000

9. Room area (sq ft) · Number · ID 9
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.

( {Length:1} * {Width:2} )

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 AC / BTU sizing calculator.