diff --git a/Raccoon.Ninja.Domain.Core.Tests/Calculators/Handlers/TimeInRangeCalculatorHandlerTests.cs b/Raccoon.Ninja.Domain.Core.Tests/Calculators/Handlers/TimeInRangeCalculatorHandlerTests.cs
new file mode 100644
index 0000000..92456bc
--- /dev/null
+++ b/Raccoon.Ninja.Domain.Core.Tests/Calculators/Handlers/TimeInRangeCalculatorHandlerTests.cs
@@ -0,0 +1,123 @@
+using Raccoon.Ninja.Domain.Core.Calculators;
+using Raccoon.Ninja.Domain.Core.Calculators.Handlers;
+
+namespace Raccoon.Ninja.Domain.Core.Tests.Calculators.Handlers;
+
+public class TimeInRangeCalculatorHandlerTests
+{
+    private readonly TimeInRangeCalculatorHandler _sut = new();
+
+    [Fact]
+    public void RunCalculation_ShouldReturnCorrectPercentages_WithValidData()
+    {
+        // Arrange
+        var data = new CalculationData
+        {
+            GlucoseValues = new List<float> { 70, 90, 150, 200, 260 }
+        };
+
+        // Act
+        var result = _sut.Handle(data);
+
+        // Assert
+        result.TimeInRange.Low.Should().Be(20);
+        result.TimeInRange.Normal.Should().Be(40);
+        result.TimeInRange.High.Should().Be(20);
+        result.TimeInRange.VeryHigh.Should().Be(20);
+    }
+
+    [Fact]
+    public void RunCalculation_ShouldHandleSingleValue()
+    {
+        // Arrange
+        var data = new CalculationData
+        {
+            GlucoseValues = new List<float> { 150 }
+        };
+
+        // Act
+        var result = _sut.Handle(data);
+
+        // Assert
+        result.TimeInRange.Low.Should().Be(0);
+        result.TimeInRange.Normal.Should().Be(100);
+        result.TimeInRange.High.Should().Be(0);
+        result.TimeInRange.VeryHigh.Should().Be(0);
+    }
+
+    [Fact]
+    public void RunCalculation_ShouldHandleAllLowValues()
+    {
+        // Arrange
+        var data = new CalculationData
+        {
+            GlucoseValues = new List<float> { 70, 75, 80, 60, 85 }
+        };
+
+        // Act
+        var result = _sut.Handle(data);
+
+        // Assert
+        result.TimeInRange.Low.Should().Be(80);
+        result.TimeInRange.Normal.Should().Be(20);
+        result.TimeInRange.High.Should().Be(0);
+        result.TimeInRange.VeryHigh.Should().Be(0);
+    }
+
+    [Fact]
+    public void RunCalculation_ShouldHandleAllNormalValues()
+    {
+        // Arrange
+        var data = new CalculationData
+        {
+            GlucoseValues = new List<float> { 90, 100, 150, 160, 170 }
+        };
+
+        // Act
+        var result = _sut.Handle(data);
+
+        // Assert
+        result.TimeInRange.Low.Should().Be(0);
+        result.TimeInRange.Normal.Should().Be(100);
+        result.TimeInRange.High.Should().Be(0);
+        result.TimeInRange.VeryHigh.Should().Be(0);
+    }
+
+    [Fact]
+    public void RunCalculation_ShouldHandleAllHighValues()
+    {
+        // Arrange
+        var data = new CalculationData
+        {
+            GlucoseValues = new List<float> { 180, 185, 200, 240, 250 }
+        };
+
+        // Act
+        var result = _sut.Handle(data);
+
+        // Assert
+        result.TimeInRange.Low.Should().Be(0);
+        result.TimeInRange.Normal.Should().Be(0);
+        result.TimeInRange.High.Should().Be(100);
+        result.TimeInRange.VeryHigh.Should().Be(0);
+    }
+
+    [Fact]
+    public void RunCalculation_ShouldHandleAllVeryHighValues()
+    {
+        // Arrange
+        var data = new CalculationData
+        {
+            GlucoseValues = new List<float> { 260, 270, 280, 290, 300 }
+        };
+
+        // Act
+        var result = _sut.Handle(data);
+
+        // Assert
+        result.TimeInRange.Low.Should().Be(0);
+        result.TimeInRange.Normal.Should().Be(0);
+        result.TimeInRange.High.Should().Be(0);
+        result.TimeInRange.VeryHigh.Should().Be(100);
+    }
+}
\ No newline at end of file
diff --git a/Raccoon.Ninja.Domain.Core/Calculators/Handlers/TimeInRangeCalculatorHandler.cs b/Raccoon.Ninja.Domain.Core/Calculators/Handlers/TimeInRangeCalculatorHandler.cs
index df6a47f..5da5094 100644
--- a/Raccoon.Ninja.Domain.Core/Calculators/Handlers/TimeInRangeCalculatorHandler.cs
+++ b/Raccoon.Ninja.Domain.Core/Calculators/Handlers/TimeInRangeCalculatorHandler.cs
@@ -13,23 +13,23 @@ public class TimeInRangeCalculatorHandler: BaseCalculatorHandler
     protected override CalculationData RunCalculation(CalculationData data)
     {
         var low = data.GlucoseValues.Count(v => v < GlucoseConstants.LowGlucoseThreshold);
-        var normal = data.GlucoseValues.Count(v => v >= GlucoseConstants.LowGlucoseThreshold && v <= GlucoseConstants.HighGlucoseThreshold);
+        var normal = data.GlucoseValues.Count(v => v >= GlucoseConstants.LowGlucoseThreshold && v < GlucoseConstants.HighGlucoseThreshold);
         var high = data.GlucoseValues.Count(v => v >= GlucoseConstants.HighGlucoseThreshold && v <= GlucoseConstants.VeryHighGlucoseThreshold);
         var veryHigh = data.GlucoseValues.Count(v => v > GlucoseConstants.VeryHighGlucoseThreshold);
-
+        
         return data with
         {
             TimeInRange = new CalculationDataTimeInRange
             {
-                Low = ToPercents(low, data.Count),
-                Normal = ToPercents(normal, data.Count),
-                High = ToPercents(high, data.Count),
-                VeryHigh = ToPercents(veryHigh, data.Count)
+                Low = ToPercent(low, data.Count),
+                Normal = ToPercent(normal, data.Count),
+                High = ToPercent(high, data.Count),
+                VeryHigh = ToPercent(veryHigh, data.Count)
             }
         };
     }
 
-    private static float ToPercents(float value, float total)
+    private static float ToPercent(float value, float total)
     {
         return value / total * 100;
     }