diff --git a/Helper/QualKardHelper.php b/Helper/QualKardHelper.php
new file mode 100644
index 0000000..a0a1c53
--- /dev/null
+++ b/Helper/QualKardHelper.php
@@ -0,0 +1,121 @@
+<?php
+
+namespace Kanboard\Plugin\QualKard\Helper;
+
+use Kanboard\Core\Base;
+
+/**
+ * QualKard helper: the qualcard grading math (ported from Ruben's C program) plus the per-board gates.
+ *
+ * Scores per grade column: hairy=0.0, hard=1.3, medium=3.0, easy=5.0. The running average is
+ * M1 = (M0 + N)/2, with a new (unread) card seeded at N - 23%. The average maps to a review interval
+ * (qualcard grades G..A, 1..11 days). qualcard's H/same-day and the overdue decay are intentionally
+ * NOT ported: there is no "again now", and the Study column is itself the overdue backlog.
+ */
+class QualKardHelper extends Base
+{
+    const SCORE = array('hairy' => 0.0, 'hard' => 1.3, 'medium' => 3.0, 'easy' => 5.0);
+
+    /**
+     * Running average. New card (unread, $old === null) seeds at N - 23%; otherwise the qualcard mean.
+     */
+    public static function nextAverage($old, $score)
+    {
+        return $old === null ? ($score - 0.23 * $score) : (($old + $score) / 2.0);
+    }
+
+    /**
+     * Average -> review interval in days (qualcard grades G..A).
+     */
+    public static function intervalDays($avg)
+    {
+        if ($avg <= 0.60) {
+            return 1; // G
+        }
+        if ($avg <= 1.35) {
+            return 2; // F
+        }
+        if ($avg <= 2.20) {
+            return 3; // E
+        }
+        if ($avg <= 3.05) {
+            return 5; // D
+        }
+        if ($avg <= 3.90) {
+            return 7; // C
+        }
+        if ($avg <= 4.92) {
+            return 9; // B
+        }
+
+        return 11; // A
+    }
+
+    /**
+     * Next due timestamp: midnight, intervalDays() out.
+     */
+    public static function dueFrom($avg, $now = null)
+    {
+        $now = $now ?: time();
+
+        return strtotime('+'.self::intervalDays($avg).' days', strtotime('today', $now));
+    }
+
+    /**
+     * Mastery badge for a card's average: label + CSS class. null (unread) = "new" (yellow); otherwise
+     * a percent of 5, coloured red (<50) / green (<90) / blue (>=90).
+     *
+     * @param  float|null $avg
+     * @return array{label:string,class:string}
+     */
+    public static function badge($avg)
+    {
+        if ($avg === null) {
+            return array('label' => t('new'), 'class' => 'qk-new');
+        }
+
+        $pct = (int) round($avg / 5.0 * 100);
+        $class = $pct < 50 ? 'qk-low' : ($pct < 90 ? 'qk-mid' : 'qk-high');
+
+        return array('label' => $pct.'%', 'class' => $class);
+    }
+
+    /**
+     * Is QualKard enabled for this board?
+     *
+     * @param  int $project_id
+     * @return bool
+     */
+    public function isEnabled($project_id)
+    {
+        return (int) $this->projectMetadataModel->get($project_id, 'qualkard_enabled', 0) === 1;
+    }
+
+    /**
+     * Is the RecoReco plugin installed? (QualKard needs its move engine.)
+     *
+     * @return bool
+     */
+    public function hasRecoReco()
+    {
+        foreach ($this->container['pluginLoader']->getPlugins() as $plugin) {
+            if ($plugin->getPluginName() === 'RecoReco') {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * The column id stored for a board role ('draft', 'study', 'hairy', ... , 'done').
+     *
+     * @param  int    $project_id
+     * @param  string $role
+     * @return int
+     */
+    public function col($project_id, $role)
+    {
+        return (int) $this->projectMetadataModel->get($project_id, 'qualkard_col_'.$role, 0);
+    }
+}