diff --git a/CHANGELOG.md b/CHANGELOG.md
index d4fae5c4..6f4bae1a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 ### Added
 
 - Improved the ARABIC function to also hande short-hand roman numerals
+- Added support for the FLOOR.MATH and FLOOR.PRECISE functions [#1351](https://github.com/PHPOffice/PhpSpreadsheet/pull/1351)
 
 ### Fixed
 
diff --git a/src/PhpSpreadsheet/Calculation/Calculation.php b/src/PhpSpreadsheet/Calculation/Calculation.php
index ae86a963..69f72033 100644
--- a/src/PhpSpreadsheet/Calculation/Calculation.php
+++ b/src/PhpSpreadsheet/Calculation/Calculation.php
@@ -914,6 +914,16 @@ class Calculation
             'functionCall' => [MathTrig::class, 'FLOOR'],
             'argumentCount' => '2',
         ],
+        'FLOOR.MATH' => [
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
+            'functionCall' => [MathTrig::class, 'FLOORMATH'],
+            'argumentCount' => '3',
+        ],
+        'FLOOR.PRECISE' => [
+            'category' => Category::CATEGORY_MATH_AND_TRIG,
+            'functionCall' => [MathTrig::class, 'FLOORPRECISE'],
+            'argumentCount' => '2',
+        ],
         'FORECAST' => [
             'category' => Category::CATEGORY_STATISTICAL,
             'functionCall' => [Statistical::class, 'FORECAST'],
diff --git a/src/PhpSpreadsheet/Calculation/MathTrig.php b/src/PhpSpreadsheet/Calculation/MathTrig.php
index 73403686..590ad99b 100644
--- a/src/PhpSpreadsheet/Calculation/MathTrig.php
+++ b/src/PhpSpreadsheet/Calculation/MathTrig.php
@@ -438,6 +438,80 @@ class MathTrig
         return Functions::VALUE();
     }
 
+    /**
+     * FLOOR.MATH.
+     *
+     * Round a number down to the nearest integer or to the nearest multiple of significance.
+     *
+     * Excel Function:
+     *        FLOOR.MATH(number[,significance[,mode]])
+     *
+     * @category Mathematical and Trigonometric Functions
+     *
+     * @param float $number Number to round
+     * @param float $significance Significance
+     * @param int $mode direction to round negative numbers
+     *
+     * @return float|string Rounded Number, or a string containing an error
+     */
+    public static function FLOORMATH($number, $significance = null, $mode = 0)
+    {
+        $number = Functions::flattenSingleValue($number);
+        $significance = Functions::flattenSingleValue($significance);
+        $mode = Functions::flattenSingleValue($mode);
+
+        if (is_numeric($number) && $significance === null) {
+            $significance = $number / abs($number);
+        }
+
+        if (is_numeric($number) && is_numeric($significance) && is_numeric($mode)) {
+            if ($significance == 0.0) {
+                return Functions::DIV0();
+            } elseif ($number == 0.0) {
+                return 0.0;
+            } elseif (self::SIGN($significance) == -1 || (self::SIGN($number) == -1 && !empty($mode))) {
+                return ceil($number / $significance) * $significance;
+            }
+
+            return floor($number / $significance) * $significance;
+        }
+
+        return Functions::VALUE();
+    }
+
+    /**
+     * FLOOR.PRECISE.
+     *
+     * Rounds number down, toward zero, to the nearest multiple of significance.
+     *
+     * Excel Function:
+     *        FLOOR.PRECISE(number[,significance])
+     *
+     * @category Mathematical and Trigonometric Functions
+     *
+     * @param float $number Number to round
+     * @param float $significance Significance
+     *
+     * @return float|string Rounded Number, or a string containing an error
+     */
+    public static function FLOORPRECISE($number, $significance = 1)
+    {
+        $number = Functions::flattenSingleValue($number);
+        $significance = Functions::flattenSingleValue($significance);
+
+        if ((is_numeric($number)) && (is_numeric($significance))) {
+            if ($significance == 0.0) {
+                return Functions::DIV0();
+            } elseif ($number == 0.0) {
+                return 0.0;
+            }
+
+            return floor($number / abs($significance)) * abs($significance);
+        }
+
+        return Functions::VALUE();
+    }
+
     private static function evaluateGCD($a, $b)
     {
         return $b ? self::evaluateGCD($b, $a % $b) : $a;
diff --git a/src/PhpSpreadsheet/Calculation/functionlist.txt b/src/PhpSpreadsheet/Calculation/functionlist.txt
index 7776e6ea..77fd4ee0 100644
--- a/src/PhpSpreadsheet/Calculation/functionlist.txt
+++ b/src/PhpSpreadsheet/Calculation/functionlist.txt
@@ -139,6 +139,8 @@ FISHER
 FISHERINV
 FIXED
 FLOOR
+FLOOR.MATH
+FLOOR.PRECISE
 FORECAST
 FREQUENCY
 FTEST
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorMathTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorMathTest.php
new file mode 100644
index 00000000..0e693e80
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorMathTest.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
+
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
+use PhpOffice\PhpSpreadsheet\Calculation\MathTrig;
+use PHPUnit\Framework\TestCase;
+
+class FloorMathTest extends TestCase
+{
+    public function setUp()
+    {
+        Functions::setCompatibilityMode(Functions::COMPATIBILITY_EXCEL);
+    }
+
+    /**
+     * @dataProvider providerFLOORMATH
+     *
+     * @param mixed $expectedResult
+     */
+    public function testFLOORMATH($expectedResult, ...$args)
+    {
+        $result = MathTrig::FLOORMATH(...$args);
+        $this->assertEquals($expectedResult, $result, '', 1E-12);
+    }
+
+    public function providerFLOORMATH()
+    {
+        return require 'data/Calculation/MathTrig/FLOORMATH.php';
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorPreciseTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorPreciseTest.php
new file mode 100644
index 00000000..616cb43b
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/MathTrig/FloorPreciseTest.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\MathTrig;
+
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
+use PhpOffice\PhpSpreadsheet\Calculation\MathTrig;
+use PHPUnit\Framework\TestCase;
+
+class FloorPreciseTest extends TestCase
+{
+    public function setUp()
+    {
+        Functions::setCompatibilityMode(Functions::COMPATIBILITY_EXCEL);
+    }
+
+    /**
+     * @dataProvider providerFLOORPRECISE
+     *
+     * @param mixed $expectedResult
+     */
+    public function testFLOOR($expectedResult, ...$args)
+    {
+        $result = MathTrig::FLOORPRECISE(...$args);
+        $this->assertEquals($expectedResult, $result, '', 1E-12);
+    }
+
+    public function providerFLOORPRECISE()
+    {
+        return require 'data/Calculation/MathTrig/FLOORPRECISE.php';
+    }
+}
diff --git a/tests/data/Calculation/MathTrig/FLOORMATH.php b/tests/data/Calculation/MathTrig/FLOORMATH.php
new file mode 100644
index 00000000..691b5245
--- /dev/null
+++ b/tests/data/Calculation/MathTrig/FLOORMATH.php
@@ -0,0 +1,89 @@
+<?php
+
+return [
+    [
+        2,
+        2.5,
+        1,
+    ],
+    [
+        -4,
+        -2.5,
+        -2,
+    ],
+    [
+        -4,
+        -2.5,
+        2,
+    ],
+    [
+        2,
+        2.5,
+        -2,
+    ],
+    [
+        '#DIV/0!',
+        123.456,
+        0,
+    ],
+    [
+        1.5,
+        1.5,
+        0.10000000000000001,
+    ],
+    [
+        0.23000000000000001,
+        0.23400000000000001,
+        0.01,
+    ],
+    [
+        123,
+        123.456,
+    ],
+    [
+        '#VALUE!',
+        'ABC',
+    ],
+    [
+        15,
+        17,
+        3,
+    ],
+    [
+        16,
+        19,
+        4,
+    ],
+    [
+        20,
+        24.3,
+        5
+    ],
+    [
+        6,
+        6.7
+    ],
+    [
+        -10,
+        -8.1,
+        2
+    ],
+    [
+        -4,
+        -5.5,
+        2,
+        -1
+    ],
+    [
+        -4,
+        -5.5,
+        2,
+        1
+    ],
+    [
+        -6,
+        -5.5,
+        2,
+        0
+    ],
+];
diff --git a/tests/data/Calculation/MathTrig/FLOORPRECISE.php b/tests/data/Calculation/MathTrig/FLOORPRECISE.php
new file mode 100644
index 00000000..4cefd984
--- /dev/null
+++ b/tests/data/Calculation/MathTrig/FLOORPRECISE.php
@@ -0,0 +1,57 @@
+<?php
+
+return [
+    [
+        2,
+        2.5,
+        1,
+    ],
+    [
+        -4,
+        -2.5,
+        -2,
+    ],
+    [
+        -4,
+        -2.5,
+        2,
+    ],
+    [
+        2,
+        2.5,
+        -2,
+    ],
+    [
+        '#DIV/0!',
+        123.456,
+        0,
+    ],
+    [
+        1.5,
+        1.5,
+        0.10000000000000001,
+    ],
+    [
+        0.23000000000000001,
+        0.23400000000000001,
+        0.01,
+    ],
+    [
+        123,
+        123.456,
+    ],
+    [
+        '#VALUE!',
+        'ABC',
+    ],
+    [
+        15,
+        17,
+        3,
+    ],
+    [
+        16,
+        19,
+        4,
+    ],
+];