Index: Riskeer/Common/src/Riskeer.Common.Forms/Helpers/ProbabilityParsingHelper.cs
===================================================================
diff -u -rbaf3c6613fea1a4f12451bad110647573050dd75 -r5f48daec42d433dee498af00bde38ccb1cecb5a3
--- Riskeer/Common/src/Riskeer.Common.Forms/Helpers/ProbabilityParsingHelper.cs	(.../ProbabilityParsingHelper.cs)	(revision baf3c6613fea1a4f12451bad110647573050dd75)
+++ Riskeer/Common/src/Riskeer.Common.Forms/Helpers/ProbabilityParsingHelper.cs	(.../ProbabilityParsingHelper.cs)	(revision 5f48daec42d433dee498af00bde38ccb1cecb5a3)
@@ -48,12 +48,13 @@
 
             try
             {
-                if (!value.StartsWith(returnPeriodNotation))
+                string trimmedString = value.Trim();
+                if (!trimmedString.StartsWith(returnPeriodNotation))
                 {
                     return Convert.ToDouble(value);
                 }
-
-                string returnPeriodValue = value.Substring(2).ToLower();
+                
+                string returnPeriodValue = trimmedString.Substring(2).ToLower();
                 return returnPeriodValue != CommonBaseResources.RoundedDouble_ToString_PositiveInfinity.ToLower()
                            ? 1 / Convert.ToDouble(returnPeriodValue)
                            : 0.0;
Index: Riskeer/Common/test/Riskeer.Common.Forms.Test/Helpers/ProbabilityParsingHelperTest.cs
===================================================================
diff -u -r9111b22be47e41193ab7bd5d3e1c06aa8dffee1a -r5f48daec42d433dee498af00bde38ccb1cecb5a3
--- Riskeer/Common/test/Riskeer.Common.Forms.Test/Helpers/ProbabilityParsingHelperTest.cs	(.../ProbabilityParsingHelperTest.cs)	(revision 9111b22be47e41193ab7bd5d3e1c06aa8dffee1a)
+++ Riskeer/Common/test/Riskeer.Common.Forms.Test/Helpers/ProbabilityParsingHelperTest.cs	(.../ProbabilityParsingHelperTest.cs)	(revision 5f48daec42d433dee498af00bde38ccb1cecb5a3)
@@ -46,7 +46,7 @@
         
         [Test]
         [SetCulture("nl-NL")]
-        [TestCase("1/25", 0.04)]
+        [TestCase("1/25     ", 0.04)]
         [TestCase("1/2,500", 0.4)]
         [TestCase("1/2.500", 0.0004)]
         [TestCase("1e-3", 0.001)]
@@ -56,9 +56,9 @@
         [TestCase("1/oneINdig", 0.0)]
         [TestCase("1/-1.000", -0.001)]
         [TestCase("1/-10", -0.1)]
-        [TestCase("1/-2,5", -0.4)]
-        [TestCase("-0,5", -0.5)]
-        [TestCase("-1", -1.0)]
+        [TestCase("    1/-2,5", -0.4)]
+        [TestCase("    -0,5", -0.5)]
+        [TestCase("-1     ", -1.0)]
         [TestCase("-1e-2", -0.01)]
         public void Parse_ValidStringInDutchCulture_ReturnsExpectedOutput(string value, double expectedProbability)
         {
@@ -71,6 +71,7 @@
 
         [Test]
         [SetCulture("en-US")]
+        [TestCase("1/25     ", 0.04)]
         [TestCase("1/25", 0.04)]
         [TestCase("1/2.5", 0.4)]
         [TestCase("1e-3", 0.001)]
@@ -80,9 +81,9 @@
         [TestCase("1/oneINdig", 0.0)]
         [TestCase("1/-1,000", -0.001)]
         [TestCase("1/-10", -0.1)]
-        [TestCase("1/-2.5", -0.4)]
-        [TestCase("-0.5", -0.5)]
-        [TestCase("-1", -1.0)]
+        [TestCase("    1/-2.5", -0.4)]
+        [TestCase("    -0.5", -0.5)]
+        [TestCase("-1     ", -1.0)]
         [TestCase("-1e-2", -0.01)]
         public void Parse_ValidStringInEnglishCulture_ReturnsExpectedOutput(string value, double expectedProbability)
         {
@@ -109,10 +110,12 @@
         }
 
         [Test]
-        public void Parse_ValueTooLargeToStoreInDouble_ThrowsProbabilityParsingException()
+        [TestCase("1")]
+        [TestCase("-1")]
+        public void Parse_ValueTooLargeToStoreInDouble_ThrowsProbabilityParsingException(string prefix)
         {
             // Setup
-            string invalidValue = "1" + double.MaxValue.ToString(CultureInfo.CurrentCulture);
+            string invalidValue = prefix + double.MaxValue.ToString(CultureInfo.CurrentCulture);
 
             // Call
             void Call() => ProbabilityParsingHelper.Parse(invalidValue);