diff --git a/poi/src/main/java/org/apache/poi/ss/formula/functions/CeilingMath.java b/poi/src/main/java/org/apache/poi/ss/formula/functions/CeilingMath.java
index a5784c5f32..7a38feae34 100644
--- a/poi/src/main/java/org/apache/poi/ss/formula/functions/CeilingMath.java
+++ b/poi/src/main/java/org/apache/poi/ss/formula/functions/CeilingMath.java
@@ -48,7 +48,7 @@ public final class CeilingMath implements FreeRefFunction {
         try {
             Double xval = evaluateValue(args[0], ec.getRowIndex(), ec.getColumnIndex());
             if (xval == null) {
-                return ErrorEval.NUM_ERROR;
+                return ErrorEval.VALUE_INVALID;
             }
             double multiplier = 1.0;
             if (args.length > 1) {
diff --git a/poi/src/main/java/org/apache/poi/ss/formula/functions/FloorMath.java b/poi/src/main/java/org/apache/poi/ss/formula/functions/FloorMath.java
index 71376f4cb1..84d51abc6f 100644
--- a/poi/src/main/java/org/apache/poi/ss/formula/functions/FloorMath.java
+++ b/poi/src/main/java/org/apache/poi/ss/formula/functions/FloorMath.java
@@ -48,7 +48,7 @@ public final class FloorMath implements FreeRefFunction {
         try {
             Double xval = evaluateValue(args[0], ec.getRowIndex(), ec.getColumnIndex());
             if (xval == null) {
-                return ErrorEval.NUM_ERROR;
+                return ErrorEval.VALUE_INVALID;
             }
             double multiplier = 1.0;
             if (args.length > 1) {
diff --git a/poi/src/main/java/org/apache/poi/ss/formula/functions/MathX.java b/poi/src/main/java/org/apache/poi/ss/formula/functions/MathX.java
index 6362ab461b..2df9e1f083 100644
--- a/poi/src/main/java/org/apache/poi/ss/formula/functions/MathX.java
+++ b/poi/src/main/java/org/apache/poi/ss/formula/functions/MathX.java
@@ -240,6 +240,8 @@ final class MathX {
                 return 0.0;
             } else if (s == 1.0) {
                 return Math.floor(n);
+            } else if (s < 0.0 && n >= 0.0) {
+                return Double.NaN;
             } else {
                 return scaledRoundUsingBigDecimal(n, s, RoundingMode.FLOOR);
             }
diff --git a/poi/src/test/java/org/apache/poi/ss/formula/functions/TestCeilingMath.java b/poi/src/test/java/org/apache/poi/ss/formula/functions/TestCeilingMath.java
index 9eb744ccb6..d8707fd8f3 100644
--- a/poi/src/test/java/org/apache/poi/ss/formula/functions/TestCeilingMath.java
+++ b/poi/src/test/java/org/apache/poi/ss/formula/functions/TestCeilingMath.java
@@ -73,7 +73,7 @@ final class TestCeilingMath {
             HSSFRow row = sheet.createRow(0);
             HSSFCell cell = row.createCell(0);
             HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
-            assertError(fe, cell, "CEILING.MATH(\"abc\")", FormulaError.NUM);
+            assertError(fe, cell, "CEILING.MATH(\"abc\")", FormulaError.VALUE);
         }
     }
 }
diff --git a/poi/src/test/java/org/apache/poi/ss/formula/functions/TestFloor.java b/poi/src/test/java/org/apache/poi/ss/formula/functions/TestFloor.java
new file mode 100644
index 0000000000..3b3b7868c1
--- /dev/null
+++ b/poi/src/test/java/org/apache/poi/ss/formula/functions/TestFloor.java
@@ -0,0 +1,78 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+package org.apache.poi.ss.formula.functions;
+
+import org.apache.poi.hssf.usermodel.HSSFCell;
+import org.apache.poi.hssf.usermodel.HSSFFormulaEvaluator;
+import org.apache.poi.hssf.usermodel.HSSFRow;
+import org.apache.poi.hssf.usermodel.HSSFSheet;
+import org.apache.poi.hssf.usermodel.HSSFWorkbook;
+import org.apache.poi.ss.formula.FormulaParseException;
+import org.apache.poi.ss.usermodel.FormulaError;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+
+import static org.apache.poi.ss.util.Utils.assertDouble;
+import static org.apache.poi.ss.util.Utils.assertError;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+/**
+ * Tests for Floor function
+ */
+final class TestFloor {
+
+    //https://support.microsoft.com/en-us/office/floor-function-14bb497c-24f2-4e04-b327-b0b4de5a8886
+    @Test
+    void testMicrosoftExamples() throws IOException {
+        try (HSSFWorkbook wb = new HSSFWorkbook()) {
+            HSSFSheet sheet = wb.createSheet();
+            HSSFRow row = sheet.createRow(0);
+            HSSFCell cell = row.createCell(0);
+            HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+            assertDouble(fe, cell, "FLOOR(3.7,2)", 2.0, 0.00000000000001);
+            assertDouble(fe, cell, "FLOOR(-2.5,-2)", -2.0, 0.00000000000001);
+            assertError(fe, cell, "FLOOR(2.5,-2)", FormulaError.NUM);
+            assertDouble(fe, cell, "FLOOR(1.58,0.1)", 1.5, 0.00000000000001);
+            assertDouble(fe, cell, "FLOOR(0.234,0.01)", 0.23, 0.00000000000001);
+        }
+    }
+
+    @Test
+    void testInvalid() throws IOException {
+        try (HSSFWorkbook wb = new HSSFWorkbook()) {
+            HSSFSheet sheet = wb.createSheet();
+            HSSFRow row = sheet.createRow(0);
+            HSSFCell cell = row.createCell(0);
+            HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+            assertThrows(FormulaParseException.class, () ->
+                assertError(fe, cell, "FLOOR()", FormulaError.VALUE));
+        }
+    }
+
+    @Test
+    void testInvalidNum() throws IOException {
+        try (HSSFWorkbook wb = new HSSFWorkbook()) {
+            HSSFSheet sheet = wb.createSheet();
+            HSSFRow row = sheet.createRow(0);
+            HSSFCell cell = row.createCell(0);
+            HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+            assertError(fe, cell, "FLOOR(\"abc\", \"def\")", FormulaError.VALUE);
+        }
+    }
+}
diff --git a/poi/src/test/java/org/apache/poi/ss/formula/functions/TestFloorMath.java b/poi/src/test/java/org/apache/poi/ss/formula/functions/TestFloorMath.java
index 3b038625d9..9dd9edf1b0 100644
--- a/poi/src/test/java/org/apache/poi/ss/formula/functions/TestFloorMath.java
+++ b/poi/src/test/java/org/apache/poi/ss/formula/functions/TestFloorMath.java
@@ -73,7 +73,7 @@ final class TestFloorMath {
             HSSFRow row = sheet.createRow(0);
             HSSFCell cell = row.createCell(0);
             HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
-            assertError(fe, cell, "FLOOR.MATH(\"abc\")", FormulaError.NUM);
+            assertError(fe, cell, "FLOOR.MATH(\"abc\")", FormulaError.VALUE);
         }
     }
 }