diff --git a/src/Entity/Parts/Part.php b/src/Entity/Parts/Part.php
index 6eed1b13..e3921fd0 100644
--- a/src/Entity/Parts/Part.php
+++ b/src/Entity/Parts/Part.php
@@ -271,6 +271,7 @@ class Part extends AttachmentContainingDBElement
     /**
      * @var float|null How much a single part unit weighs in gramms.
      * @ORM\Column(type="float", nullable=true)
+     * @Assert\Positive()
      */
     protected $mass;
 
diff --git a/src/Services/SIFormatter.php b/src/Services/SIFormatter.php
new file mode 100644
index 00000000..965fd2ee
--- /dev/null
+++ b/src/Services/SIFormatter.php
@@ -0,0 +1,93 @@
+<?php
+/**
+ *
+ * part-db version 0.1
+ * Copyright (C) 2005 Christoph Lechner
+ * http://www.cl-projects.de/
+ *
+ * part-db version 0.2+
+ * Copyright (C) 2009 K. Jacobs and others (see authors.php)
+ * http://code.google.com/p/part-db/
+ *
+ * Part-DB Version 0.4+
+ * Copyright (C) 2016 - 2019 Jan Böhmer
+ * https://github.com/jbtronics
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
+ *
+ */
+
+namespace App\Services;
+
+/**
+ * A service that helps you to format values using the SI prefixes.
+ * @package App\Services
+ */
+class SIFormatter
+{
+    /**
+     * Returns the magnitude of a value (the count of decimal place of the highest decimal place).
+     * For example, for 100 (=10^2) this function returns 2. For -2500 (=-2.5*10^3) this function returns 3.
+     * @param float $value The value of which the magnitude should be determined.
+     * @return int The magnitude of the value
+     */
+    public function getMagnitude(float $value) : int
+    {
+        return (int) floor(log10(abs($value)));
+    }
+
+    /**
+     * Returns the best SI prefix (and its corresponding divisor) for the given magnitude.
+     * @param int $magnitude The magnitude for which the prefix should be determined.
+     * @return array A array, containing the divisor in first element, and the prefix symbol in second. For example, [1000, "k"].
+     */
+    public function getPrefixByMagnitude(int $magnitude) : array
+    {
+        $prefixes_pos = ['' ,'k', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y'];
+        $prefixes_neg = ['' ,'m', 'μ', 'n', 'p', 'f', 'a', 'z', 'y'];
+
+        //Determine nearest prefix index.
+        $nearest = (int) round(abs($magnitude) / 3);
+
+        if ($magnitude >= 0) {
+            $symbol = $prefixes_pos[$nearest];
+        } else {
+            $symbol = $prefixes_neg[$nearest];
+        }
+
+        if ($magnitude < 0) {
+            $nearest *= -1;
+        }
+
+        return [10 ** (3 * $nearest), $symbol];
+    }
+
+    /**
+     * @param float $value
+     * @param string $unit
+     * @param int $decimals
+     * @return string
+     */
+    public function format(float $value, string $unit = '', int $decimals = 2)
+    {
+        [$divisor, $symbol] = $this->getPrefixByMagnitude($this->getMagnitude($value));
+        $value /= $divisor;
+        //Build the format string, e.g.: %.2d km
+        $format_string = '%.' . $decimals . 'f ' . $symbol . $unit;
+
+        return sprintf($format_string, $value);
+    }
+
+}
\ No newline at end of file
diff --git a/src/Twig/AppExtension.php b/src/Twig/AppExtension.php
index 549823eb..f348b342 100644
--- a/src/Twig/AppExtension.php
+++ b/src/Twig/AppExtension.php
@@ -33,6 +33,7 @@ use App\Entity\Attachments\Attachment;
 use App\Entity\Base\DBElement;
 use App\Services\EntityURLGenerator;
 use App\Services\MoneyFormatter;
+use App\Services\SIFormatter;
 use App\Services\TreeBuilder;
 use Symfony\Component\Cache\Adapter\AdapterInterface;
 use Symfony\Component\Serializer\SerializerInterface;
@@ -49,16 +50,19 @@ class AppExtension extends AbstractExtension
     protected $serializer;
     protected $treeBuilder;
     protected $moneyFormatter;
+    protected $siformatter;
 
     public function __construct(EntityURLGenerator $entityURLGenerator, AdapterInterface $cache,
                                 SerializerInterface $serializer, TreeBuilder $treeBuilder,
-                                MoneyFormatter $moneyFormatter)
+                                MoneyFormatter $moneyFormatter,
+                                SIFormatter $SIFormatter)
     {
         $this->entityURLGenerator = $entityURLGenerator;
         $this->cache = $cache;
         $this->serializer = $serializer;
         $this->treeBuilder = $treeBuilder;
         $this->moneyFormatter = $moneyFormatter;
+        $this->siformatter = $SIFormatter;
     }
 
     public function getFilters()
@@ -66,7 +70,8 @@ class AppExtension extends AbstractExtension
         return [
             new TwigFilter('entityURL', [$this, 'generateEntityURL']),
             new TwigFilter('bbCode', [$this, 'parseBBCode'], ['pre_escape' => 'html', 'is_safe' => ['html']]),
-            new TwigFilter('moneyFormat', [$this, 'formatCurrency'])
+            new TwigFilter('moneyFormat', [$this, 'formatCurrency']),
+            new TwigFilter('siFormat', [$this, 'siFormat']),
         ];
     }
 
@@ -117,4 +122,9 @@ class AppExtension extends AbstractExtension
     {
         return $this->moneyFormatter->format($amount, $currency);
     }
+
+    public function siFormat($value, $unit, $decimals = 2)
+    {
+        return $this->siformatter->format($value, $unit, $decimals);
+    }
 }
diff --git a/templates/Parts/info/_sidebar.html.twig b/templates/Parts/info/_sidebar.html.twig
index 3b1bfd48..b299ff73 100644
--- a/templates/Parts/info/_sidebar.html.twig
+++ b/templates/Parts/info/_sidebar.html.twig
@@ -10,6 +10,15 @@
 </span>
 </div>
 
+{# Part mass #}
+{% if part.mass %}
+    <div>
+        <h6>
+            <span class="badge badge-secondary" title="{% trans %}part.mass.tooltip{% endtrans %}"><i class="fas fa-weight-hanging fa-fw"></i> {{ part.mass | siFormat("g") }}</span>
+        </h6>
+    </div>
+{% endif %}
+
 {# Needs Review tag #}
 {% if part.needsReview %}
     <div class="mt-1">
diff --git a/tests/Entity/PermissionsEmbedTest.php b/tests/Entity/PermissionsEmbedTest.php
index 1690e5a3..999d2146 100644
--- a/tests/Entity/PermissionsEmbedTest.php
+++ b/tests/Entity/PermissionsEmbedTest.php
@@ -31,7 +31,7 @@
 
 namespace App\Tests\Entity;
 
-use App\Entity\PermissionsEmbed;
+use App\Entity\UserSystem\PermissionsEmbed;
 use Doctrine\ORM\Mapping\Embedded;
 use PHPUnit\Framework\TestCase;
 
diff --git a/tests/Services/PermissionResolverTest.php b/tests/Services/PermissionResolverTest.php
index 0c0a9d75..eca6ba39 100644
--- a/tests/Services/PermissionResolverTest.php
+++ b/tests/Services/PermissionResolverTest.php
@@ -32,9 +32,9 @@
 namespace App\Tests\Services;
 
 
-use App\Entity\Group;
-use App\Entity\PermissionsEmbed;
-use App\Entity\User;
+use App\Entity\UserSystem\Group;
+use App\Entity\UserSystem\PermissionsEmbed;
+use App\Entity\UserSystem\User;
 use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;
 use App\Services\PermissionResolver;
 use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;
diff --git a/tests/Services/SIFormatterTest.php b/tests/Services/SIFormatterTest.php
new file mode 100644
index 00000000..405b68e1
--- /dev/null
+++ b/tests/Services/SIFormatterTest.php
@@ -0,0 +1,91 @@
+<?php
+/**
+ *
+ * part-db version 0.1
+ * Copyright (C) 2005 Christoph Lechner
+ * http://www.cl-projects.de/
+ *
+ * part-db version 0.2+
+ * Copyright (C) 2009 K. Jacobs and others (see authors.php)
+ * http://code.google.com/p/part-db/
+ *
+ * Part-DB Version 0.4+
+ * Copyright (C) 2016 - 2019 Jan Böhmer
+ * https://github.com/jbtronics
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
+ *
+ */
+
+namespace App\Tests\Services;
+
+use App\Services\SIFormatter;
+use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;
+
+class SIFormatterTest extends WebTestCase
+{
+    /**
+     * @var SIFormatter
+     */
+    protected $service;
+
+    public function setUp()
+    {
+        //Get an service instance.
+        self::bootKernel();
+        //$this->service = self::$container->get(SIFormatter::class);
+
+        $this->service = new SIFormatter();
+    }
+
+    public function testGetMagnitude()
+    {
+        //Get an service instance.
+        $this->assertSame(0, $this->service->getMagnitude(7.0));
+        $this->assertSame(0, $this->service->getMagnitude(9.0));
+        $this->assertSame(0, $this->service->getMagnitude(0.0));
+        $this->assertSame(0, $this->service->getMagnitude(-1.0));
+        $this->assertSame(0, $this->service->getMagnitude(-9.9));
+
+
+        $this->assertSame(3, $this->service->getMagnitude(9999.99));
+        $this->assertSame(3, $this->service->getMagnitude(1000.0));
+        $this->assertSame(3, $this->service->getMagnitude(-9999.99));
+        $this->assertSame(3, $this->service->getMagnitude(-1000.0));
+
+        $this->assertSame(-1, $this->service->getMagnitude(0.1));
+        $this->assertSame(-1, $this->service->getMagnitude(-0.9999));
+
+        $this->assertSame(-25, $this->service->getMagnitude(- 1.246e-25));
+        $this->assertSame(12, $this->service->getMagnitude(9.99e12));
+    }
+
+    public function testgetPrefixByMagnitude()
+    {
+        $this->assertSame([1000, 'k'], $this->service->getPrefixByMagnitude(3));
+        $this->assertSame([1000, 'k'], $this->service->getPrefixByMagnitude(2));
+        $this->assertSame([1000, 'k'], $this->service->getPrefixByMagnitude(4));
+
+        $this->assertSame([0.001, 'm'], $this->service->getPrefixByMagnitude(-3));
+        $this->assertSame([0.001, 'm'], $this->service->getPrefixByMagnitude(-2));
+        $this->assertSame([0.001, 'm'], $this->service->getPrefixByMagnitude(-4));
+    }
+
+    public function testFormat()
+    {
+        $this->assertSame("2.32 km", $this->service->format(2321, 'm'));
+        $this->assertSame("-98.20 mg", $this->service->format(-0.0982, 'g'));
+    }
+}
\ No newline at end of file