Index: Ringtoets/Revetment/src/Ringtoets.Revetment.Data/Ringtoets.Revetment.Data.csproj
===================================================================
diff -u -r8b7420d9b5ced2565ae07009fc8b5af8e1b8d5e7 -r8d4b9f33c5cc447619dc028293676e78003783e3
--- Ringtoets/Revetment/src/Ringtoets.Revetment.Data/Ringtoets.Revetment.Data.csproj	(.../Ringtoets.Revetment.Data.csproj)	(revision 8b7420d9b5ced2565ae07009fc8b5af8e1b8d5e7)
+++ Ringtoets/Revetment/src/Ringtoets.Revetment.Data/Ringtoets.Revetment.Data.csproj	(.../Ringtoets.Revetment.Data.csproj)	(revision 8d4b9f33c5cc447619dc028293676e78003783e3)
@@ -20,6 +20,7 @@
     </Compile>
     <Compile Include="WaveConditionsInput.cs" />
     <Compile Include="WaveConditionsInputExtensions.cs" />
+    <Compile Include="WaveConditionsInputHelper.cs" />
     <Compile Include="WaveConditionsInputStepSize.cs" />
     <Compile Include="WaveConditionsInputStepSizeExtensions.cs" />
     <Compile Include="WaveConditionsOutput.cs" />
Index: Ringtoets/Revetment/src/Ringtoets.Revetment.Data/WaveConditionsInputHelper.cs
===================================================================
diff -u
--- Ringtoets/Revetment/src/Ringtoets.Revetment.Data/WaveConditionsInputHelper.cs	(revision 0)
+++ Ringtoets/Revetment/src/Ringtoets.Revetment.Data/WaveConditionsInputHelper.cs	(revision 8d4b9f33c5cc447619dc028293676e78003783e3)
@@ -0,0 +1,44 @@
+// Copyright (C) Stichting Deltares 2017. All rights reserved.
+//
+// This file is part of Ringtoets.
+//
+// Ringtoets is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+//
+// All names, logos, and references to "Deltares" are registered trademarks of
+// Stichting Deltares and remain full property of Stichting Deltares at all times.
+// All rights reserved.
+
+using Core.Common.Base.Data;
+
+namespace Ringtoets.Revetment.Data
+{
+    /// <summary>
+    /// Class containing helper methods related to <see cref="WaveConditionsInput"/>.
+    /// </summary>
+    public static class WaveConditionsInputHelper
+    {
+        private const double designWaterLevelSubstraction = 0.01;
+
+        /// <summary>
+        /// Gets an upper boundary based on the provided assessment level (that can be used while
+        /// determining water levels for wave condition calculations).
+        /// </summary>
+        /// <param name="assessmentLevel">The assessment level at stake.</param>
+        /// <returns>The corresponding design water level upper boundary.</returns>
+        public static RoundedDouble GetUpperBoundaryDesignWaterLevel(RoundedDouble assessmentLevel)
+        {
+            return new RoundedDouble(2, assessmentLevel - designWaterLevelSubstraction);
+        }
+    }
+}
\ No newline at end of file
Index: Ringtoets/Revetment/test/Ringtoets.Revetment.Data.Test/Ringtoets.Revetment.Data.Test.csproj
===================================================================
diff -u -r8b7420d9b5ced2565ae07009fc8b5af8e1b8d5e7 -r8d4b9f33c5cc447619dc028293676e78003783e3
--- Ringtoets/Revetment/test/Ringtoets.Revetment.Data.Test/Ringtoets.Revetment.Data.Test.csproj	(.../Ringtoets.Revetment.Data.Test.csproj)	(revision 8b7420d9b5ced2565ae07009fc8b5af8e1b8d5e7)
+++ Ringtoets/Revetment/test/Ringtoets.Revetment.Data.Test/Ringtoets.Revetment.Data.Test.csproj	(.../Ringtoets.Revetment.Data.Test.csproj)	(revision 8d4b9f33c5cc447619dc028293676e78003783e3)
@@ -18,6 +18,7 @@
     <Compile Include="GeneralWaveConditionsInputTest.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="WaveConditionsInputExtensionsTest.cs" />
+    <Compile Include="WaveConditionsInputHelperTest.cs" />
     <Compile Include="WaveConditionsInputStepSizeExtensionsTest.cs" />
     <Compile Include="WaveConditionsInputStepSizeTest.cs" />
     <Compile Include="WaveConditionsInputTest.cs" />
Index: Ringtoets/Revetment/test/Ringtoets.Revetment.Data.Test/WaveConditionsInputHelperTest.cs
===================================================================
diff -u
--- Ringtoets/Revetment/test/Ringtoets.Revetment.Data.Test/WaveConditionsInputHelperTest.cs	(revision 0)
+++ Ringtoets/Revetment/test/Ringtoets.Revetment.Data.Test/WaveConditionsInputHelperTest.cs	(revision 8d4b9f33c5cc447619dc028293676e78003783e3)
@@ -0,0 +1,44 @@
+// Copyright (C) Stichting Deltares 2017. All rights reserved.
+//
+// This file is part of Ringtoets.
+//
+// Ringtoets is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+//
+// All names, logos, and references to "Deltares" are registered trademarks of
+// Stichting Deltares and remain full property of Stichting Deltares at all times.
+// All rights reserved.
+
+using Core.Common.Base.Data;
+using NUnit.Framework;
+
+namespace Ringtoets.Revetment.Data.Test
+{
+    [TestFixture]
+    public class WaveConditionsInputHelperTest
+    {
+        [TestCase(-0.5, -0.51)]
+        [TestCase(0.0, -0.01)]
+        [TestCase(0.5, 0.49)]
+        [TestCase(double.NaN, double.NaN)]
+        public void GetUpperBoundaryDesignWaterLevel_DifferentAssessmentLevels_ReturnsExpectedUpperBoundary(double assessmentLevel, double expectedUpperBoundary)
+        {
+            // Call
+            RoundedDouble upperBoundary = WaveConditionsInputHelper.GetUpperBoundaryDesignWaterLevel((RoundedDouble) assessmentLevel);
+
+            // Assert
+            Assert.AreEqual(2, upperBoundary.NumberOfDecimalPlaces);
+            Assert.AreEqual(expectedUpperBoundary, upperBoundary);
+        }
+    }
+}
\ No newline at end of file