diff --git a/ClosedXML/Excel/CalcEngine/Functions/MathTrig.cs b/ClosedXML/Excel/CalcEngine/Functions/MathTrig.cs
index 2d1368d..c6ef569 100644
--- a/ClosedXML/Excel/CalcEngine/Functions/MathTrig.cs
+++ b/ClosedXML/Excel/CalcEngine/Functions/MathTrig.cs
@@ -4,6 +4,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text;
 
 namespace ClosedXML.Excel.CalcEngine
 {
@@ -25,6 +26,7 @@
             ce.RegisterFunction("COMBIN", 2, Combin);
             ce.RegisterFunction("COS", 1, Cos);
             ce.RegisterFunction("COSH", 1, Cosh);
+            ce.RegisterFunction("DECIMAL", 2, MathTrig.Decimal);
             ce.RegisterFunction("DEGREES", 1, Degrees);
             ce.RegisterFunction("EVEN", 1, Even);
             ce.RegisterFunction("EXP", 1, Exp);
@@ -115,6 +117,37 @@
             return Math.Cosh(p[0]);
         }
 
+        private static object Decimal(List<Expression> p)
+        {
+            string source = p[0];
+            double radix = p[1];
+
+            if (radix < 2 || radix > 36)
+                throw new NumberException();
+
+            var asciiValues = Encoding.ASCII.GetBytes(source.ToUpperInvariant());
+
+            double result = 0;
+            int i = 0;
+
+            foreach (byte digit in asciiValues)
+            {
+                int digitNumber = digit >= 48 && digit < 58
+                    ? digit - 48
+                    : digit > 90
+                        ? throw new NumberException()
+                        : digit - 55;
+
+                if (digitNumber > radix - 1)
+                    throw new NumberException();
+
+                result = result * radix + digitNumber;
+                i++;
+            }
+
+            return result;
+        }
+
         private static object Exp(List<Expression> p)
         {
             return Math.Exp(p[0]);
diff --git a/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs b/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs
index b9003d2..6cfe211 100644
--- a/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs
+++ b/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs
@@ -1,4 +1,5 @@
 using ClosedXML.Excel;
+using ClosedXML.Excel.CalcEngine;
 using ClosedXML.Excel.CalcEngine.Exceptions;
 using NUnit.Framework;
 using System;
@@ -11,6 +12,33 @@
     {
         private readonly double tolerance = 1e-10;
 
+        [TestCase("FF", 16, 255)]
+        [TestCase("111", 2, 7)]
+        [TestCase("zap", 36, 45745)]
+        public void Decimal(string inputString, int radix, int expectedResult)
+        {
+            var actualResult = XLWorkbook.EvaluateExpr($"DECIMAL(\"{inputString}\", {radix})");
+            Assert.AreEqual(expectedResult, actualResult);
+        }
+
+        [Test]
+        public void Decimal_ZeroIsZeroInAnyRadix([Range(1, 36)] int radix)
+        {
+            Assert.AreEqual(0, XLWorkbook.EvaluateExpr($"DECIMAL(\"0\", {radix})"));
+        }
+
+        [Theory]
+        public void Decimal_ReturnsErrorForRadiansGreater36([Range(37, 255)] int radix)
+        {
+            Assert.Throws<NumberException>(() => XLWorkbook.EvaluateExpr($"DECIMAL(\"0\", {radix})"));
+        }
+
+        [Theory]
+        public void Decimal_ReturnsErrorForRadiansSmaller2([Range(-5, 1)] int radix)
+        {
+            Assert.Throws<NumberException>(() => XLWorkbook.EvaluateExpr($"DECIMAL(\"0\", {radix})"));
+        }
+
         [Test]
         public void Floor()
         {