diff --git a/ClosedXML/Excel/CalcEngine/Functions/MathTrig.cs b/ClosedXML/Excel/CalcEngine/Functions/MathTrig.cs
index b042a5e..43b2786 100644
--- a/ClosedXML/Excel/CalcEngine/Functions/MathTrig.cs
+++ b/ClosedXML/Excel/CalcEngine/Functions/MathTrig.cs
@@ -24,6 +24,7 @@
             ce.RegisterFunction("ATANH", 1, Atanh);
             ce.RegisterFunction("CEILING", 1, Ceiling);
             ce.RegisterFunction("COMBIN", 2, Combin);
+            ce.RegisterFunction("COMBINA", 2, CombinA);
             ce.RegisterFunction("COS", 1, Cos);
             ce.RegisterFunction("COSH", 1, Cosh);
             ce.RegisterFunction("COT", 1, Cot);
@@ -421,6 +422,24 @@
             return XLMath.Combin(n, k);
         }
 
+        private static object CombinA(List<Expression> p)
+        {
+            Int32 number = (int)p[0]; // casting truncates towards 0 as specified
+            Int32 chosen = (int)p[1];
+
+            if (number < 0 || number < chosen)
+                throw new NumberException();
+            if (chosen < 0)
+                throw new NumberException();
+
+            int n = number + chosen - 1;
+            int k = number - 1;
+
+            return n == k || k == 0
+                ? 1
+                : (long)XLMath.Combin(n, k);
+        }
+
         private static object Degrees(List<Expression> p)
         {
             return p[0] * (180.0 / Math.PI);
diff --git a/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs b/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs
index be8bb17..e005e38 100644
--- a/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs
+++ b/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs
@@ -1,5 +1,4 @@
 using ClosedXML.Excel;
-using ClosedXML.Excel.CalcEngine;
 using ClosedXML.Excel.CalcEngine.Exceptions;
 using NUnit.Framework;
 using System;
@@ -12,7 +11,42 @@
     public class MathTrigTests
     {
         private readonly double tolerance = 1e-10;
-        
+
+        [TestCase(4, 3, 20)]
+        [TestCase(10, 3, 220)]
+        [TestCase(0, 0, 1)]
+        public void Combina_CalculatesCorrectValues(int number, int chosen, int expectedResult)
+        {
+            var actualResult = XLWorkbook.EvaluateExpr($"COMBINA({number}, {chosen})");
+            Assert.AreEqual(expectedResult, (long)actualResult);
+        }
+
+        [Theory]
+        public void Combina_Returns1WhenChosenIs0([Range(0, 10)]int number)
+        {
+            Combina_CalculatesCorrectValues(number, 0, 1);
+        }
+
+        [TestCase(4.23, 3, 20)]
+        [TestCase(10.4, 3.14, 220)]
+        [TestCase(0, 0.4, 1)]
+        public void Combina_TruncatesNumbersCorrectly(double number, double chosen, int expectedResult)
+        {
+            var actualResult = XLWorkbook.EvaluateExpr(string.Format(
+                @"COMBINA({0}, {1})",
+                number.ToString(CultureInfo.InvariantCulture),
+                chosen.ToString(CultureInfo.InvariantCulture)));
+
+            Assert.AreEqual(expectedResult, (long)actualResult);
+        }
+
+        [TestCase(-1, 2)]
+        [TestCase(0, 0)]
+        public void Combina_ThrowsNumExceptionOnInvalidValues(int number, int chosen)
+        {
+            Assert.Throws<NumberException>(() => XLWorkbook.EvaluateExpr($"COMBINA({number}, {chosen})"));
+        }
+
         [TestCase(1, 0.642092616)]
         [TestCase(2, -0.457657554)]
         [TestCase(3, -7.015252551)]