diff -r 296caca18161 -r 3d61397fe9cd www/js/rec_edit.js
--- a/www/js/rec_edit.js	Fri Feb 08 11:30:22 2019 +0100
+++ b/www/js/rec_edit.js	Sat Feb 09 15:43:13 2019 +0100
@@ -989,32 +989,35 @@
 		$("#sparge_acid_amount").val(Acid);
 	}
 
+	/*
+	 * Change OG of recipe but keep the water volumes.
+	 */
 	function calcFermentablesFromOG(OG) {
 
 		console.log("calcFermentablesFromOG("+OG+")");
-		var	efficiency = parseFloat($("#efficiency").jqxNumberInput('decimal'));
-		var	rows = $('#fermentableGrid').jqxGrid('getrows');
-		var	sug = sg_to_plato(OG) * parseFloat($("#batch_size").jqxNumberInput('decimal')) * OG / 100;	//total amount of sugars in kg
-		var	tot = 0;
-		for (var i = 0; i < rows.length; i++) {
-			var row = rows[i];
+		var efficiency = parseFloat($("#efficiency").jqxNumberInput('decimal'));
+		var sug = sg_to_plato(OG) * parseFloat($("#batch_size").jqxNumberInput('decimal')) * OG / 100;	//total amount of sugars in kg
+		var tot = 0;
+		var rowscount = $("#fermentableGrid").jqxGrid('getdatainformation').rowscount;
+
+		for (var i = 0; i < rowscount; i++) {
+			var row = $("#fermentableGrid").jqxGrid('getrowdata', i);
 			var d = row.f_percentage / 100 * (row.f_yield / 100) * (1 - row.f_moisture / 100);
 			if (row.f_added == 0)	// Mash
 				d = efficiency / 100 * d;
 			tot += d;
 		}
-
 		var	totmass = 0;
 		if (tot)
 			totmass = sug / tot;
 
 		if (totmass) {
-			for (var i = 0; i < rows.length; i++) {
-				var row = rows[i];
-				$("#fermentableGrid").jqxGrid('setcellvalue', i, "f_amount", row.f_percentage / 100 * totmass);
+			for (i = 0; i < rowscount; i++) {
+				var row = $("#fermentableGrid").jqxGrid('getrowdata', i);
+				var amount = row.f_percentage / 100 * totmass;
+				$("#fermentableGrid").jqxGrid('setcellvalue', i, "f_amount", amount);
 			}
 		}
-		//CalcWaterBalance;
 	};
 
 	function calcFG() {