diff -r 8dc0a00b1db4 -r 107c12c3e49d www/js/global.js
--- a/www/js/global.js	Thu Nov 15 17:17:33 2018 +0100
+++ b/www/js/global.js	Thu Nov 15 22:22:51 2018 +0100
@@ -171,6 +171,36 @@
 
 
 
+function sg_to_plato(sg) {
+	if (sg > 0.5)
+		return 259 - 259 / sg;
+	return 0;
+}
+
+
+
+function plato_to_sg(plato) {
+	if (plato < 259)
+		return 259 / (259 - plato);
+	return 1.000;
+}
+
+
+
+function estimate_sg(sugars, batch_size) {
+	var plato = 100 * sugars / batch_size;
+
+	var sg = plato_to_sg(plato);
+	for (var i = 0; i < 20; i++) {
+		if (sg > 0)
+			plato = 100 * sugars / (batch_size * sg);
+		sg = plato_to_sg(plato);
+	}
+	console.log("estimate_sg(" + sugars + "," + batch_size + ") : " + sg);
+	return sg;
+}
+
+
 /*
  * Steinie:
  *