diff -r 0aef416dbceb -r f4e00869f39f www/includes/formulas.php
--- a/www/includes/formulas.php	Fri Apr 17 11:29:37 2020 +0200
+++ b/www/includes/formulas.php	Sat Apr 18 11:12:28 2020 +0200
@@ -132,6 +132,14 @@
 
 
 
+function calc_svg($og, $fg) {
+	$oe = sg_to_plato($og);
+	$ae = sg_to_plato($fg);
+	return ($oe - $ae) / $oe * 100;
+}
+
+
+
 /*
  * sugars is the total extract weight of sugars.
  */