diff --git a/src/Spout/Common/Entity/Style/Style.php b/src/Spout/Common/Entity/Style/Style.php
index b34e036..ab9ec8e 100644
--- a/src/Spout/Common/Entity/Style/Style.php
+++ b/src/Spout/Common/Entity/Style/Style.php
@@ -71,6 +71,12 @@ class Style
     /** @var bool */
     private $hasSetBackgroundColor = false;
 
+    /** @var string Format */
+    private $format = null;
+
+    /** @var bool */
+    private $hasSetFormat = false;
+
     /**
      * @return int|null
      */
@@ -383,4 +389,34 @@ class Style
     {
         return $this->hasSetBackgroundColor;
     }
+
+    /**
+     * Sets format
+     * @param string $format
+     * @return Style
+     */
+    public function setFormat($format)
+    {
+        $this->hasSetFormat = true;
+        $this->format = $format;
+
+        return $this;
+    }
+
+    /**
+     * @return string
+     */
+    public function getFormat()
+    {
+        return $this->format;
+    }
+
+    /**
+     *
+     * @return bool Whether format should be applied
+     */
+    public function shouldApplyFormat()
+    {
+        return $this->hasSetFormat;
+    }
 }
diff --git a/src/Spout/Writer/Common/Creator/Style/StyleBuilder.php b/src/Spout/Writer/Common/Creator/Style/StyleBuilder.php
index a35a280..ffe4814 100644
--- a/src/Spout/Writer/Common/Creator/Style/StyleBuilder.php
+++ b/src/Spout/Writer/Common/Creator/Style/StyleBuilder.php
@@ -147,6 +147,18 @@ class StyleBuilder
 
         return $this;
     }
+    /**
+     *  Sets a format
+     *
+     * @api
+     * @param string $format Format
+     * @return StyleBuilder
+     */
+    public function setFormat($format)
+    {
+        $this->style->setFormat($format);
+        return $this;
+    }
 
     /**
      * Returns the configured style. The style is cached and can be reused.
diff --git a/src/Spout/Writer/Common/Manager/Style/StyleMerger.php b/src/Spout/Writer/Common/Manager/Style/StyleMerger.php
index d3446d2..1628783 100644
--- a/src/Spout/Writer/Common/Manager/Style/StyleMerger.php
+++ b/src/Spout/Writer/Common/Manager/Style/StyleMerger.php
@@ -88,6 +88,9 @@ class StyleMerger
         if (!$style->getBorder() && $baseStyle->shouldApplyBorder()) {
             $styleToUpdate->setBorder($baseStyle->getBorder());
         }
+        if (!$style->getFormat() && $baseStyle->shouldApplyFormat()) {
+            $styleToUpdate->setFormat($baseStyle->getFormat());
+        }
         if (!$style->shouldApplyBackgroundColor() && $baseStyle->shouldApplyBackgroundColor()) {
             $styleToUpdate->setBackgroundColor($baseStyle->getBackgroundColor());
         }
diff --git a/src/Spout/Writer/XLSX/Manager/Style/StyleManager.php b/src/Spout/Writer/XLSX/Manager/Style/StyleManager.php
index b98307a..b7491a9 100644
--- a/src/Spout/Writer/XLSX/Manager/Style/StyleManager.php
+++ b/src/Spout/Writer/XLSX/Manager/Style/StyleManager.php
@@ -33,7 +33,10 @@ class StyleManager extends \Box\Spout\Writer\Common\Manager\Style\StyleManager
         $associatedBorderId = $this->styleRegistry->getBorderIdForStyleId($styleId);
         $hasStyleCustomBorders = ($associatedBorderId !== null && $associatedBorderId !== 0);
 
-        return ($hasStyleCustomFill || $hasStyleCustomBorders);
+        $associatedFormatId = $this->styleRegistry->getFormatIdForStyleId($styleId);
+        $hasStyleCustomFormats = ($associatedFormatId !== null && $associatedFormatId !== 0);
+
+        return ($hasStyleCustomFill || $hasStyleCustomBorders || $hasStyleCustomFormats);
     }
 
     /**
@@ -48,6 +51,7 @@ class StyleManager extends \Box\Spout\Writer\Common\Manager\Style\StyleManager
 <styleSheet xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
 EOD;
 
+        $content .= $this->getFormatsSectionContent();
         $content .= $this->getFontsSectionContent();
         $content .= $this->getFillsSectionContent();
         $content .= $this->getBordersSectionContent();
@@ -62,6 +66,35 @@ EOD;
         return $content;
     }
 
+    /**
+     * Returns the content of the "<numFmts>" section.
+     *
+     * @return string
+     */
+    protected function getFormatsSectionContent()
+    {
+        $tags = [];
+        $registeredFormats = $this->styleRegistry->getRegisteredFormats();
+        foreach ($registeredFormats as $styleId) {
+            $numFmtId = $this->styleRegistry->getFormatIdForStyleId($styleId);
+
+            //Built-in formats do not need to be declared, skip them
+            if ($numFmtId < 164) {
+                continue;
+            }
+
+            /** @var Style $style */
+            $style = $this->styleRegistry->getStyleFromStyleId($styleId);
+            $format = $style->getFormat();
+            $tags[] = '<numFmt numFmtId="' . $numFmtId . '" formatCode="' . $format . '"/>';
+        }
+        $content = '<numFmts count="' . count($tags) . '">';
+        $content .= implode('', $tags);
+        $content .= '</numFmts>';
+
+        return $content;
+    }
+
     /**
      * Returns the content of the "<fonts>" section.
      *
@@ -206,8 +239,9 @@ EOD;
             $styleId = $style->getId();
             $fillId = $this->getFillIdForStyleId($styleId);
             $borderId = $this->getBorderIdForStyleId($styleId);
+            $numFmtId = $this->getFormatIdForStyleId($styleId);
 
-            $content .= '<xf numFmtId="0" fontId="' . $styleId . '" fillId="' . $fillId . '" borderId="' . $borderId . '" xfId="0"';
+            $content .= '<xf numFmtId="' . $numFmtId . '" fontId="' . $styleId . '" fillId="' . $fillId . '" borderId="' . $borderId . '" xfId="0"';
 
             if ($style->shouldApplyFont()) {
                 $content .= ' applyFont="1"';
@@ -261,6 +295,22 @@ EOD;
         return $isDefaultStyle ? 0 : ($this->styleRegistry->getBorderIdForStyleId($styleId) ?: 0);
     }
 
+    /**
+     * Returns the format ID associated to the given style ID.
+     * For the default style use general format.
+     *
+     * @param int $styleId
+     * @return int
+     */
+    private function getFormatIdForStyleId($styleId)
+    {
+        // For the default style (ID = 0), we don't want to override the format.
+        // Otherwise all cells of the spreadsheet will have a format.
+        $isDefaultStyle = ($styleId === 0);
+
+        return $isDefaultStyle ? 0 : ($this->styleRegistry->getFormatIdForStyleId($styleId) ?: 0);
+    }
+
     /**
      * Returns the content of the "<cellStyles>" section.
      *
diff --git a/src/Spout/Writer/XLSX/Manager/Style/StyleRegistry.php b/src/Spout/Writer/XLSX/Manager/Style/StyleRegistry.php
index abd89f1..ae47cd7 100644
--- a/src/Spout/Writer/XLSX/Manager/Style/StyleRegistry.php
+++ b/src/Spout/Writer/XLSX/Manager/Style/StyleRegistry.php
@@ -10,6 +10,81 @@ use Box\Spout\Common\Entity\Style\Style;
  */
 class StyleRegistry extends \Box\Spout\Writer\Common\Manager\Style\StyleRegistry
 {
+    /**
+     * @see https://msdn.microsoft.com/en-us/library/ff529597(v=office.12).aspx
+     * @var array Mapping between built-in format and the associated numFmtId
+     */
+    protected static $builtinNumFormatToIdMapping = [
+
+        'General' => 0,
+        '0' => 1,
+        '0.00' => 2,
+        '#,##0' => 3,
+        '#,##0.00' => 4,
+        '$#,##0,\-$#,##0' => 5,
+        '$#,##0,[Red]\-$#,##0' => 6,
+        '$#,##0.00,\-$#,##0.00' => 7,
+        '$#,##0.00,[Red]\-$#,##0.00' => 8,
+        '0%' => 9,
+        '0.00%' => 10,
+        '0.00E+00' => 11,
+        '# ?/?' => 12,
+        '# ??/??' => 13,
+        'mm-dd-yy' => 14,
+        'd-mmm-yy' => 15,
+        'd-mmm' => 16,
+        'mmm-yy' => 17,
+        'h:mm AM/PM' => 18,
+        'h:mm:ss AM/PM' => 19,
+        'h:mm' => 20,
+        'h:mm:ss' => 21,
+        'm/d/yy h:mm' => 22,
+
+        '#,##0 ,(#,##0)' => 37,
+        '#,##0 ,[Red](#,##0)' => 38,
+        '#,##0.00,(#,##0.00)' => 39,
+        '#,##0.00,[Red](#,##0.00)' => 40,
+
+        '_("$"* #,##0.00_),_("$"* \(#,##0.00\),_("$"* "-"??_),_(@_)' => 44,
+        'mm:ss' => 45,
+        '[h]:mm:ss' => 46,
+        'mm:ss.0' => 47,
+
+        '##0.0E+0' => 48,
+        '@' => 49,
+
+        '[$-404]e/m/d' => 27,
+        'm/d/yy' => 30,
+        't0' => 59,
+        't0.00' => 60,
+        't#,##0' => 61,
+        't#,##0.00' => 62,
+        't0%' => 67,
+        't0.00%' => 68,
+        't# ?/?' => 69,
+        't# ??/??' => 70,
+    ];
+
+
+    /**
+     * @var array
+     */
+    protected $registeredFormats = [];
+
+    /**
+     * @var array [STYLE_ID] => [FORMAT_ID] maps a style to a format declaration
+     */
+    protected $styleIdToFormatsMappingTable = [];
+
+    /**
+     * If the numFmtId is lower than 0xA4 (164 in decimal)
+     * then it's a built-in number format.
+     * Since Excel is the dominant vendor - we play along here
+     *
+     * @var int The fill index counter for custom fills.
+     */
+    protected $formatIndex = 164;
+
     /**
      * @var array
      */
@@ -48,11 +123,58 @@ class StyleRegistry extends \Box\Spout\Writer\Common\Manager\Style\StyleRegistry
     {
         $registeredStyle = parent::registerStyle($style);
         $this->registerFill($registeredStyle);
+        $this->registerFormat($registeredStyle);;
         $this->registerBorder($registeredStyle);
 
         return $registeredStyle;
     }
 
+    /**
+     * Register a format definition
+     *
+     * @param Style $style
+     */
+    protected function registerFormat(Style $style)
+    {
+        $styleId = $style->getId();
+
+        $format = $style->getFormat();
+        if ($format) {
+            $isFormatRegistered = isset($this->registeredFormats[$format]);
+
+            // We need to track the already registered format definitions
+            if ($isFormatRegistered) {
+                $registeredStyleId = $this->registeredFormats[$format];
+                $registeredFormatId = $this->styleIdToFormatsMappingTable[$registeredStyleId];
+                $this->styleIdToFormatsMappingTable[$styleId] = $registeredFormatId;
+            } else {
+                $this->registeredFormats[$format] = $styleId;
+                if (isset(self::$builtinNumFormatToIdMapping[$format])) {
+                    $id = self::$builtinNumFormatToIdMapping[$format];
+                } else {
+                    $id = $this->formatIndex++;
+                }
+                $this->styleIdToFormatsMappingTable[$styleId] = $id;
+            }
+
+        } else {
+            // The formatId maps a style to a format declaration
+            // When there is no format definition - we default to 0 ( General )
+            $this->styleIdToFormatsMappingTable[$styleId] = 0;
+        }
+    }
+
+    /**
+     * @param int $styleId
+     * @return int|null Format ID associated to the given style ID
+     */
+    public function getFormatIdForStyleId($styleId)
+    {
+        return (isset($this->styleIdToFormatsMappingTable[$styleId])) ?
+            $this->styleIdToFormatsMappingTable[$styleId] :
+            null;
+    }
+
     /**
      * Register a fill definition
      *
@@ -136,6 +258,7 @@ class StyleRegistry extends \Box\Spout\Writer\Common\Manager\Style\StyleRegistry
             null;
     }
 
+
     /**
      * @return array
      */
@@ -151,4 +274,14 @@ class StyleRegistry extends \Box\Spout\Writer\Common\Manager\Style\StyleRegistry
     {
         return $this->registeredBorders;
     }
+
+
+    /**
+     * @return array
+     */
+    public function getRegisteredFormats()
+    {
+        return $this->registeredFormats;
+    }
+
 }
diff --git a/tests/Spout/Writer/XLSX/WriterWithStyleTest.php b/tests/Spout/Writer/XLSX/WriterWithStyleTest.php
index 02e6d11..a724e2b 100644
--- a/tests/Spout/Writer/XLSX/WriterWithStyleTest.php
+++ b/tests/Spout/Writer/XLSX/WriterWithStyleTest.php
@@ -210,6 +210,47 @@ class WriterWithStyleTest extends TestCase
         $this->assertEquals('1', $cellDomElements[1]->getAttribute('s'));
     }
 
+    /**
+     * @return void
+     */
+    public function testAddRowWithNumFmtStyles()
+    {
+        $fileName = 'test_add_row_with_numfmt.xlsx';
+        $style = (new StyleBuilder())
+            ->setFontBold()
+            ->setFormat('0.00')//Builtin format
+            ->build();
+        $style2 = (new StyleBuilder())
+            ->setFontBold()
+            ->setFormat('0.000')
+            ->build();
+
+
+        $dataRows = [
+            $this->createStyledRowFromValues([1.123456789], $style),
+            $this->createStyledRowFromValues([12.1], $style2),
+        ];
+
+        $this->writeToXLSXFile($dataRows, $fileName);
+
+
+        $formatsDomElement = $this->getXmlSectionFromStylesXmlFile($fileName, 'numFmts');
+        $this->assertEquals(
+            1,
+            $formatsDomElement->getAttribute('count'),
+            'There should be 2 formats, including the 1 default ones'
+        );
+
+
+        $cellXfsDomElement = $this->getXmlSectionFromStylesXmlFile($fileName, 'cellXfs');
+
+        foreach ([2, 164] as $index => $expected) {
+            $xfElement = $cellXfsDomElement->getElementsByTagName('xf')->item($index + 1);
+            $this->assertEquals($expected, $xfElement->getAttribute('numFmtId'));
+
+        }
+    }
+
     /**
      * @return void
      */