diff --git a/mailpoet/lib/Form/Block/BlockRendererHelper.php b/mailpoet/lib/Form/Block/BlockRendererHelper.php
index 91232f4d32..f20acc93eb 100644
--- a/mailpoet/lib/Form/Block/BlockRendererHelper.php
+++ b/mailpoet/lib/Form/Block/BlockRendererHelper.php
@@ -188,8 +188,8 @@ class BlockRendererHelper {
   public function renderFontStyle(array $formSettings, array $styles = []) {
     $rules = [];
     if (isset($formSettings['fontSize'])) {
-      $rules[] = 'font-size: ' . trim($formSettings['fontSize']) . 'px;';
-      $rules[] = 'line-height: ' . (float)trim($formSettings['fontSize']) * 1.2 . 'px";';
+      $rules[] = 'font-size: ' . $formSettings['fontSize'] . (is_numeric($formSettings['fontSize']) ? "px;" : ";");
+      $rules[] = 'line-height: 1.2;';
     }
     if (isset($styles['bold'])) {
       $rules[] = 'font-weight: bold;';
diff --git a/mailpoet/lib/Form/Block/Heading.php b/mailpoet/lib/Form/Block/Heading.php
index f1b7ef90a1..f24ac6f1af 100644
--- a/mailpoet/lib/Form/Block/Heading.php
+++ b/mailpoet/lib/Form/Block/Heading.php
@@ -93,7 +93,7 @@ class Heading {
       $styles[] = 'color: ' . $block['params']['text_color'];
     }
     if (!empty($block['params']['font_size'])) {
-      $styles[] = 'font-size: ' . $block['params']['font_size'] . 'px';
+      $styles[] = 'font-size: ' . $block['params']['font_size'] . (is_numeric($block['params']['font_size']) ? 'px' : '');
     }
     if (!empty($block['params']['line_height'])) {
       $styles[] = 'line-height: ' . $block['params']['line_height'];
diff --git a/mailpoet/lib/Form/Block/Paragraph.php b/mailpoet/lib/Form/Block/Paragraph.php
index 239279c118..f13286f21f 100644
--- a/mailpoet/lib/Form/Block/Paragraph.php
+++ b/mailpoet/lib/Form/Block/Paragraph.php
@@ -78,7 +78,7 @@ class Paragraph {
       $styles[] = 'color: ' . $block['params']['text_color'];
     }
     if (!empty($block['params']['font_size'])) {
-      $styles[] = 'font-size: ' . $block['params']['font_size'] . 'px';
+      $styles[] = 'font-size: ' . $block['params']['font_size'] . (is_numeric($block['params']['font_size']) ? 'px' : '');
     }
     if (!empty($block['params']['line_height'])) {
       $styles[] = 'line-height: ' . $block['params']['line_height'];
diff --git a/mailpoet/lib/Form/BlockStylesRenderer.php b/mailpoet/lib/Form/BlockStylesRenderer.php
index 2c5bff558c..13f3ec7b7b 100644
--- a/mailpoet/lib/Form/BlockStylesRenderer.php
+++ b/mailpoet/lib/Form/BlockStylesRenderer.php
@@ -48,10 +48,10 @@ class BlockStylesRenderer {
       $rules[] = "font-family:'{$formSettings['font_family']}';" ;
     }
     if (isset($styles['font_size'])) {
-      $rules[] = "font-size:" . intval($styles['font_size']) . "px;";
+      $rules[] = "font-size:" . $styles['font_size'] . (is_numeric($styles['font_size']) ? "px;" : ";");
     }
     if (isset($formSettings['fontSize']) && !isset($styles['font_size'])) {
-      $rules[] = "font-size:" . intval($formSettings['fontSize']) . "px;";
+      $rules[] = "font-size:" . $formSettings['fontSize'] . (is_numeric($formSettings['fontSize']) ? "px;" : ";");
     }
     if (isset($formSettings['fontSize']) || isset($styles['font_size'])) {
       $rules[] = "line-height:1.5;";
diff --git a/mailpoet/tests/unit/Form/Block/BlockRendererHelperTest.php b/mailpoet/tests/unit/Form/Block/BlockRendererHelperTest.php
index 5e55515e9e..368801541a 100644
--- a/mailpoet/tests/unit/Form/Block/BlockRendererHelperTest.php
+++ b/mailpoet/tests/unit/Form/Block/BlockRendererHelperTest.php
@@ -58,6 +58,12 @@ class BlockRendererHelperTest extends \MailPoetUnitTest {
     $block['params']['hide_label'] = '1';
     $label = $this->rendererHelper->renderLabel($block, []);
     expect($label)->equals('');
+
+    $label = $this->rendererHelper->renderLabel($this->block, ['fontSize' => 10]);
+    expect($label)->stringContainsString('style="font-size: 10px;');
+
+    $label = $this->rendererHelper->renderLabel($this->block, ['fontSize' => '1.2em']);
+    expect($label)->stringContainsString('style="font-size: 1.2em;');
   }
 
   public function testItShouldRenderLegend() {
diff --git a/mailpoet/tests/unit/Form/Block/HeadingTest.php b/mailpoet/tests/unit/Form/Block/HeadingTest.php
index b195b5c80e..8bea8676be 100644
--- a/mailpoet/tests/unit/Form/Block/HeadingTest.php
+++ b/mailpoet/tests/unit/Form/Block/HeadingTest.php
@@ -105,6 +105,16 @@ class HeadingTest extends \MailPoetUnitTest {
     expect($html)->equals('<h2 class="mailpoet-heading mailpoet-has-font-size" style="font-size: 33px">Header</h2>');
   }
 
+  public function testItShouldRenderFontSizeWithUnit() {
+    $html = $this->heading->render([
+      'params' => [
+        'content' => 'Header',
+        'font_size' => '2.2em',
+      ],
+    ]);
+    expect($html)->equals('<h2 class="mailpoet-heading mailpoet-has-font-size" style="font-size: 2.2em">Header</h2>');
+  }
+
   public function testItShouldRenderLineHeight() {
     $html = $this->heading->render([
       'params' => [
diff --git a/mailpoet/tests/unit/Form/Block/ParagraphTest.php b/mailpoet/tests/unit/Form/Block/ParagraphTest.php
index d54a8e15e7..25a147b77a 100644
--- a/mailpoet/tests/unit/Form/Block/ParagraphTest.php
+++ b/mailpoet/tests/unit/Form/Block/ParagraphTest.php
@@ -80,6 +80,16 @@ class ParagraphTest extends \MailPoetUnitTest {
     expect($html)->equals('<p class="mailpoet_form_paragraph mailpoet-has-font-size" style="font-size: 33px">Paragraph</p>');
   }
 
+  public function testItShouldRenderFontSizeWithUnit() {
+    $html = $this->paragraph->render([
+      'params' => [
+        'content' => 'Paragraph',
+        'font_size' => '2.3em',
+      ],
+    ]);
+    expect($html)->equals('<p class="mailpoet_form_paragraph mailpoet-has-font-size" style="font-size: 2.3em">Paragraph</p>');
+  }
+
   public function testItShouldRenderLineHeight() {
     $html = $this->paragraph->render([
       'params' => [
diff --git a/mailpoet/tests/unit/Form/BlockStylesRendererTest.php b/mailpoet/tests/unit/Form/BlockStylesRendererTest.php
index 37424327e3..695dca283b 100644
--- a/mailpoet/tests/unit/Form/BlockStylesRendererTest.php
+++ b/mailpoet/tests/unit/Form/BlockStylesRendererTest.php
@@ -123,4 +123,23 @@ class BlockStylesRendererTest extends \MailPoetUnitTest {
     $result = $this->renderer->renderForButton(['font_family' => 'font2'], $settings);
     expect($result)->stringContainsString("font-family:'font2'");
   }
+
+  public function testItShouldSupportFontSizesWithUnits() {
+    $settings = [
+      'input_padding' => '40',
+      'fontSize' => '1.5rem',
+    ];
+    $result = $this->renderer->renderForButton([], $settings);
+    expect($result)->stringContainsString('font-size:1.5rem;');
+    $styles = [
+      'font_size' => '2.4em',
+    ];
+    $result = $this->renderer->renderForButton($styles, $settings);
+    expect($result)->stringContainsString('font-size:2.4em;');
+    $styles = [
+      'font_size' => '23',
+    ];
+    $result = $this->renderer->renderForButton($styles, $settings);
+    expect($result)->stringContainsString('font-size:23px;');
+  }
 }