Kode dari tutorial https://solusipress.com/format-angka-pada-calculation-field-forminator/

functions.php

<?php 
add_action( 'wp_enqueue_scripts', 'solusipress_jquery_number' );
function solusipress_jquery_number() {
	if( is_page( 'forminator-test' ) ) {
		wp_enqueue_script( 'jquery-number', 'https://businessprofile.solusipress.com/wp-content/uploads/custom-css-js/18.js' );
	}
}
add_action( 'wp_footer', 'solusipress_forminator_format_number' );
function solusipress_forminator_format_number() {
	if( is_page( 'forminator-test' ) ) { ?>
<script type="text/javascript">										
( function($){
    
	$( '#calculation-1-field' ).hide();
	$( '#calculation-1-field' ).parent().append( '<div id="total_html" style="font-weight:600;font-size:22px"></div>' );
	set_total();
	$( '#calculation-1-field' ).on( 'change', function(){
	    set_total();
	} );		
	
    function set_total() {
        var tot = $('#calculation-1-field').val();
        $( '#total_html' ).html( 'Rp' + $.number( tot, 0, ',', '.' ) );
    }	
	
} )( jQuery );	
</script><?php
	}
}