diff --git a/app/database/migrations/2015_01_05_202826_CreateMetricsTable.php b/app/database/migrations/2015_01_05_202826_CreateMetricsTable.php
index 9d784dfe..ad847728 100644
--- a/app/database/migrations/2015_01_05_202826_CreateMetricsTable.php
+++ b/app/database/migrations/2015_01_05_202826_CreateMetricsTable.php
@@ -19,6 +19,7 @@ class CreateMetricsTable extends Migration
             $table->string('suffix');
             $table->text('description');
             $table->decimal('default_value', 10, 3);
+            $table->tinyInteger('calc_type');
             $table->boolean('display_chart')->default(1);
             $table->timestamps();
 
diff --git a/app/lang/de/forms.php b/app/lang/de/forms.php
index 11f33b3f..2f597b39 100644
--- a/app/lang/de/forms.php
+++ b/app/lang/de/forms.php
@@ -58,6 +58,9 @@ return [
         'description'      => 'Description',
         'description-help' => 'You may also use Markdown.',
         'display-chart'    => 'Display chart on status page?',
+        'calc_type'        => 'Calculation of metrics',
+        'type_sum'         => 'Sum',
+        'type_avg'         => 'Average',
 
         'points' => [
             'value' => 'Value',
diff --git a/app/lang/en/forms.php b/app/lang/en/forms.php
index d2f79ee2..33b5bc8b 100644
--- a/app/lang/en/forms.php
+++ b/app/lang/en/forms.php
@@ -61,6 +61,9 @@ return [
         'description-help' => 'You may also use Markdown.',
         'display-chart'    => 'Display chart on status page?',
         'default-value'    => 'Default value',
+        'calc_type'        => 'Calculation of metrics',
+        'type_sum'         => 'Sum',
+        'type_avg'         => 'Average',
 
         'points' => [
             'value' => 'Value',
diff --git a/app/lang/es/forms.php b/app/lang/es/forms.php
index 679d4acc..328dace9 100644
--- a/app/lang/es/forms.php
+++ b/app/lang/es/forms.php
@@ -59,6 +59,9 @@ return [
         'description'      => 'Descripción',
         'description-help' => 'Puedes usar también Markdown.',
         'display-chart'    => '¿Vizualizar gráfica en la página de estado?',
+        'calc_type'        => 'Calculation of metrics',
+        'type_sum'         => 'Sum',
+        'type_avg'         => 'Average',
 
         'points' => [
             'value' => 'Valor',
diff --git a/app/lang/fr/forms.php b/app/lang/fr/forms.php
index ff9f2be9..ac023203 100644
--- a/app/lang/fr/forms.php
+++ b/app/lang/fr/forms.php
@@ -58,6 +58,9 @@ return [
         'description'      => 'Description',
         'description-help' => 'You may also use Markdown.',
         'display-chart'    => 'Display chart on status page?',
+        'calc_type'        => 'Calculation of metrics',
+        'type_sum'         => 'Sum',
+        'type_avg'         => 'Average',
 
         'points' => [
             'value' => 'Value',
diff --git a/app/lang/pt-BR/forms.php b/app/lang/pt-BR/forms.php
index a0d783b5..f9b75a23 100755
--- a/app/lang/pt-BR/forms.php
+++ b/app/lang/pt-BR/forms.php
@@ -61,6 +61,9 @@ return [
         'description-help' => '',
         'display-chart'    => '',
         'default-value'    => '',
+        'calc_type'        => 'Calculation of metrics',
+        'type_sum'         => 'Sum',
+        'type_avg'         => 'Average',
 
         'points' => [
             'value' => '',
diff --git a/app/views/dashboard/metrics/add.blade.php b/app/views/dashboard/metrics/add.blade.php
index ececbfbc..2a643292 100644
--- a/app/views/dashboard/metrics/add.blade.php
+++ b/app/views/dashboard/metrics/add.blade.php
@@ -31,6 +31,13 @@
                                 <textarea name="metric[description]" class="form-control" rows="5" required>{{ Input::old('metric.description') }}</textarea>
                             </div>
                         </div>
+                        <div class="form-group">
+                            <label>{{ trans('forms.metrics.calc_type') }}</label>
+                            <select name="metric[calc_type]" class="form-control" required>
+                                <option value="0" selected>{{ trans('forms.metrics.type_sum') }}</option>
+                                <option value="1">{{ trans('forms.metrics.type_avg') }}</option>
+                            </select>
+                        </div>
                         <div class="form-group">
                             <label for="metric-default_value">{{ trans('forms.metrics.default-value') }}</label>
                             <input type="number" class="form-control" name="metric[default_value]" id="metric-default_value" value="{{ Input::old('metric.default_value') }}">
diff --git a/app/views/dashboard/metrics/edit.blade.php b/app/views/dashboard/metrics/edit.blade.php
index b47acb1d..cb95aecb 100644
--- a/app/views/dashboard/metrics/edit.blade.php
+++ b/app/views/dashboard/metrics/edit.blade.php
@@ -31,6 +31,13 @@
                                 <textarea name="metric[description]" class="form-control" rows="5" required>{{ $metric->description }}</textarea>
                             </div>
                         </div>
+                        <div class="form-group">
+                            <label>{{ trans('forms.metrics.calc_type') }}</label>
+                            <select name="metric[calc_type]" class="form-control" required>
+                                <option value="0" {{ $metric->calc_type === 0 ? "selected" : null }}>{{ trans('forms.metrics.type_sum') }}</option>
+                                <option value="1" {{ $metric->calc_type === 1 ? "selected" : null }}>{{ trans('forms.metrics.type_avg') }}</option>
+                            </select>
+                        </div>
                         <div class="form-group">
                             <label for="metric-default_value">{{ trans('forms.metrics.default-value') }}</label>
                             <input type="number" class="form-control" name="metric[default_value]" id="metric-default_value" value="{{ $metric->default_value }}">
diff --git a/app/views/partials/metrics.blade.php b/app/views/partials/metrics.blade.php
index c9d27a29..644fc636 100644
--- a/app/views/partials/metrics.blade.php
+++ b/app/views/partials/metrics.blade.php
@@ -31,37 +31,36 @@
             </div>
         </div>
         <script>
-            var hourList = [];
-            var date = new Date();
+            (function () {
+                var hourList = [], date = new Date();
 
-            for (var i = 10; i >= 1; i--) {
-                hourList.push(moment(date).subtract(i, 'hours').seconds(0).format('HH:ss'));
-            }
+                for (var i = 10; i >= 1; i--) {
+                    hourList.push(moment(date).subtract(i, 'hours').seconds(0).format('HH:ss'));
+                }
 
-            hourList.push(moment(date).seconds(0).format('HH:ss'));
+                hourList.push(moment(date).seconds(0).format('HH:ss'));
 
-            var data = {
-                showTooltips: false,
-                labels: hourList,
-                datasets: [{
-                    fillColor: "rgba(220,220,220,0.2)",
-                    strokeColor: "rgba(220,220,220,1)",
-                    pointColor: "rgba(220,220,220,1)",
-                    pointStrokeColor: "#fff",
-                    pointHighlightFill: "#fff",
-                    pointHighlightStroke: "rgba(220,220,220,1)",
-                    data: [{{ implode(',', $points) }}]
-                }]
-            };
+                var data = {
+                    showTooltips: false,
+                    labels: hourList,
+                    datasets: [{
+                        fillColor: "rgba(220,220,220,0.2)",
+                        strokeColor: "rgba(220,220,220,1)",
+                        pointColor: "rgba(220,220,220,1)",
+                        pointStrokeColor: "#fff",
+                        pointHighlightFill: "#fff",
+                        pointHighlightStroke: "rgba(220,220,220,1)",
+                        data: [{{ implode(',', $points) }}]
+                    }]
+                };
 
-            window.onload = function() {
                 var ctx = document.getElementById("metric-{{ $metric->id }}").getContext("2d");
-                window.myLine = new Chart(ctx).Line(data, {
+                new Chart(ctx).Line(data, {
                     scaleShowVerticalLines: true,
                     pointDot: false,
                     responsive: true
                 });
-            };
+            }());
         </script>
     </li>
     @endforeach
diff --git a/src/Models/Metric.php b/src/Models/Metric.php
index 2861e86e..d84af1d3 100644
--- a/src/Models/Metric.php
+++ b/src/Models/Metric.php
@@ -24,6 +24,9 @@ class Metric extends Model implements TransformableInterface
 {
     use ValidatingTrait;
 
+    const CALC_SUM = 0;
+    const CALC_AVG = 1;
+
     /**
      * The model's attributes.
      *
@@ -32,6 +35,8 @@ class Metric extends Model implements TransformableInterface
     protected $attributes = [
         'name'          => '',
         'display_chart' => 1,
+        'default_value' => 0,
+        'calc_type'     => 0,
     ];
 
     /**
@@ -43,7 +48,7 @@ class Metric extends Model implements TransformableInterface
         'name'          => 'required',
         'suffix'        => 'required',
         'display_chart' => 'boolean',
-        'default_value' => 'numeric|required',
+        'default_value' => 'numeric',
     ];
 
     /**
@@ -51,7 +56,7 @@ class Metric extends Model implements TransformableInterface
      *
      * @var string[]
      */
-    protected $fillable = ['name', 'suffix', 'description', 'display_chart', 'default_value'];
+    protected $fillable = ['name', 'suffix', 'description', 'display_chart', 'default_value', 'calc_type'];
 
     /**
      * Metrics contain many metric points.
@@ -76,9 +81,20 @@ class Metric extends Model implements TransformableInterface
         $dateTime->sub(new DateInterval('PT'.$hour.'H'));
 
         if (Config::get('database.default') === 'mysql') {
-            $value = (int) $this->points()->whereRaw('DATE_FORMAT(created_at, "%Y%m%e%H") = '.$dateTime->format('YmdH'))->whereRaw('HOUR(created_at) = HOUR(DATE_SUB(NOW(), INTERVAL '.$hour.' HOUR))')->groupBy(DB::raw('HOUR(created_at)'))->sum('value');
+            if (! isset($this->calc_type) || $this->calc_type === self::CALC_SUM) {
+                $value = (int) $this->points()->whereRaw('DATE_FORMAT(created_at, "%Y%m%e%H") = '.$dateTime->format('YmdH'))->whereRaw('HOUR(created_at) = HOUR(DATE_SUB(NOW(), INTERVAL '.$hour.' HOUR))')->groupBy(DB::raw('HOUR(created_at)'))->sum('value');
+            } elseif ($this->calc_type === self::CALC_AVG) {
+                $value = (int) $this->points()->whereRaw('DATE_FORMAT(created_at, "%Y%m%e%H") = '.$dateTime->format('YmdH'))->whereRaw('HOUR(created_at) = HOUR(DATE_SUB(NOW(), INTERVAL '.$hour.' HOUR))')->groupBy(DB::raw('HOUR(created_at)'))->avg('value');
+            }
         } else {
-            $query = DB::select("select sum(metric_points.value) as aggregate FROM metrics JOIN metric_points ON metric_points.metric_id = metrics.id WHERE to_char(metric_points.created_at, 'YYYYMMDDHH') = :timestamp AND to_char(metric_points.created_at, 'H') = to_char(now() - interval '{$hour} hour', 'H') GROUP BY to_char(metric_points.created_at, 'H')", [
+            // Default metrics calculations.
+            if (! isset($this->calc_type) || $this->calc_type === self::CALC_SUM) {
+                $queryType = "sum(metric_points.value)";
+            } elseif ($this->calc_type === self::CALC_AVG) {
+                $queryType = "avg(metric_points.value)";
+            }
+
+            $query = DB::select("select {$queryType} as aggregate FROM metrics JOIN metric_points ON metric_points.metric_id = metrics.id WHERE to_char(metric_points.created_at, 'YYYYMMDDHH') = :timestamp AND to_char(metric_points.created_at, 'H') = to_char(now() - interval '{$hour} hour', 'H') GROUP BY to_char(metric_points.created_at, 'H')", [
                 'timestamp' => $dateTime->format('YmdH'),
             ]);