diff --git a/src/Controller/Admin/AddressBookController.php b/src/Controller/Admin/AddressBookController.php
index c43c1ebe..0e743d99 100644
--- a/src/Controller/Admin/AddressBookController.php
+++ b/src/Controller/Admin/AddressBookController.php
@@ -26,8 +26,13 @@ public function addressBooks(ManagerRegistry $doctrine, #[MapEntity(id: 'userId'
         $principal = $doctrine->getRepository(Principal::class)->findOneByUri($principalUri);
         $addressbooks = $doctrine->getRepository(AddressBook::class)->findByPrincipalUri($principalUri);
 
+        $cardCounts = $doctrine->getRepository(AddressBook::class)->countCardsByAddressBook(
+            array_map(fn (AddressBook $addressbook) => $addressbook->getId(), $addressbooks)
+        );
+
         return $this->render('addressbooks/index.html.twig', [
             'addressbooks' => $addressbooks,
+            'cardCounts' => $cardCounts,
             'principal' => $principal,
             'userId' => $userId,
         ]);
diff --git a/src/Controller/Admin/CalendarController.php b/src/Controller/Admin/CalendarController.php
index 96960fb9..71716196 100644
--- a/src/Controller/Admin/CalendarController.php
+++ b/src/Controller/Admin/CalendarController.php
@@ -30,30 +30,31 @@ public function calendars(ManagerRegistry $doctrine, UrlGeneratorInterface $rout
         $principalUri = $user->getPrincipalUri();
 
         $principal = $doctrine->getRepository(Principal::class)->findOneByUri($principalUri);
-        $allCalendars = $doctrine->getRepository(CalendarInstance::class)->findByPrincipalUri($principalUri);
+        $allCalendars = $doctrine->getRepository(CalendarInstance::class)->findByPrincipalUriWithCalendars($principalUri);
 
         $subscriptions = $doctrine->getRepository(CalendarSubscription::class)->findByPrincipalUri($principalUri);
 
+        $objectCounts = $doctrine->getRepository(CalendarInstance::class)->countObjectsByCalendar(
+            array_map(fn (CalendarInstance $instance) => $instance->getCalendar()->getId(), $allCalendars)
+        );
+
         // Separate shared calendars
         $calendars = [];
         $shared = [];
         $auto = [];
         foreach ($allCalendars as $calendar) {
+            $compoundObject = [
+                'entity' => $calendar,
+                'uri' => $router->generate('dav', ['path' => 'calendars/'.$username.'/'.$calendar->getUri()], UrlGeneratorInterface::ABSOLUTE_URL),
+                'objectCount' => $objectCounts[$calendar->getCalendar()->getId()],
+            ];
+
             if ($calendar->isAutomaticallyGenerated()) {
-                $auto[] = [
-                    'entity' => $calendar,
-                    'uri' => $router->generate('dav', ['path' => 'calendars/'.$username.'/'.$calendar->getUri()], UrlGeneratorInterface::ABSOLUTE_URL),
-                ];
+                $auto[] = $compoundObject;
             } elseif (!$calendar->isShared()) {
-                $calendars[] = [
-                    'entity' => $calendar,
-                    'uri' => $router->generate('dav', ['path' => 'calendars/'.$username.'/'.$calendar->getUri()], UrlGeneratorInterface::ABSOLUTE_URL),
-                ];
+                $calendars[] = $compoundObject;
             } else {
-                $shared[] = [
-                    'entity' => $calendar,
-                    'uri' => $router->generate('dav', ['path' => 'calendars/'.$username.'/'.$calendar->getUri()], UrlGeneratorInterface::ABSOLUTE_URL),
-                ];
+                $shared[] = $compoundObject;
             }
         }
 
diff --git a/src/Controller/Admin/UserController.php b/src/Controller/Admin/UserController.php
index 6619c422..4943bfca 100644
--- a/src/Controller/Admin/UserController.php
+++ b/src/Controller/Admin/UserController.php
@@ -152,7 +152,7 @@ public function userDelete(ManagerRegistry $doctrine, Request $request, #[MapEnt
         $principalUri = $user->getPrincipalUri();
 
         // Remove calendars and addressbooks
-        $calendars = $doctrine->getRepository(CalendarInstance::class)->findByPrincipalUri($principalUri);
+        $calendars = $doctrine->getRepository(CalendarInstance::class)->findByPrincipalUriWithCalendars($principalUri);
         foreach ($calendars ?? [] as $instance) {
             // We're only removing the calendar objects / changes / and calendar if the deleted user is an owner,
             // which means that the underlying calendar instance should not have another principal as owner.
diff --git a/src/Controller/Api/ApiController.php b/src/Controller/Api/ApiController.php
index 59908b4c..597b08a1 100644
--- a/src/Controller/Api/ApiController.php
+++ b/src/Controller/Api/ApiController.php
@@ -168,7 +168,7 @@ public function getUserCalendars(Request $request, int $userId, ManagerRegistry
             return $this->json(['status' => 'error', 'message' => 'Principal Not Found', 'timestamp' => $this->getTimestamp()], 404);
         }
 
-        $allCalendars = $doctrine->getRepository(CalendarInstance::class)->findByPrincipalUri($principalUri);
+        $allCalendars = $doctrine->getRepository(CalendarInstance::class)->findByPrincipalUriWithCalendars($principalUri);
         $allSubscriptions = $doctrine->getRepository(CalendarSubscription::class)->findByPrincipalUri($principalUri);
 
         $calendars = [];
@@ -243,7 +243,7 @@ public function getUserCalendarDetails(Request $request, int $userId, int $calen
             return $this->json(['status' => 'error', 'message' => 'Principal Not Found', 'timestamp' => $this->getTimestamp()], 404);
         }
 
-        $allCalendars = $doctrine->getRepository(CalendarInstance::class)->findByPrincipalUri($principalUri);
+        $allCalendars = $doctrine->getRepository(CalendarInstance::class)->findByPrincipalUriWithCalendars($principalUri);
 
         $calendar_details = [];
         foreach ($allCalendars as $calendar) {
diff --git a/src/Entity/AddressBook.php b/src/Entity/AddressBook.php
index 50009119..31accf52 100644
--- a/src/Entity/AddressBook.php
+++ b/src/Entity/AddressBook.php
@@ -2,13 +2,14 @@
 
 namespace App\Entity;
 
+use App\Repository\AddressBookRepository;
 use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
 use Doctrine\ORM\Mapping as ORM;
 use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
 use Symfony\Component\Validator\Constraints as Assert;
 
-#[ORM\Entity()]
+#[ORM\Entity(repositoryClass: AddressBookRepository::class)]
 #[ORM\Table(name: 'addressbooks')]
 #[UniqueEntity(fields: ['principalUri', 'uri'], errorPath: 'uri', message: 'form.uri.unique')]
 class AddressBook
diff --git a/src/Repository/AddressBookRepository.php b/src/Repository/AddressBookRepository.php
new file mode 100644
index 00000000..75e1aad3
--- /dev/null
+++ b/src/Repository/AddressBookRepository.php
@@ -0,0 +1,54 @@
+<?php
+
+namespace App\Repository;
+
+use App\Entity\AddressBook;
+use App\Entity\Card;
+use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;
+use Doctrine\Persistence\ManagerRegistry;
+
+/**
+ * @method AddressBook|null find($id, $lockMode = null, $lockVersion = null)
+ * @method AddressBook|null findOneBy(array $criteria, array $orderBy = null)
+ * @method AddressBook[]    findAll()
+ * @method AddressBook[]    findBy(array $criteria, array $orderBy = null, $limit = null, $offset = null)
+ */
+class AddressBookRepository extends ServiceEntityRepository
+{
+    public function __construct(ManagerRegistry $registry)
+    {
+        parent::__construct($registry, AddressBook::class);
+    }
+
+    /**
+     * Counts the cards of several address books at once, so that listing a principal's address
+     * books costs a single query instead of one per address book.
+     *
+     * @param int[] $addressBookIds
+     *
+     * @return array<int, int> count per address book id, including the address books that hold nothing
+     */
+    public function countCardsByAddressBook(array $addressBookIds): array
+    {
+        $counts = array_fill_keys($addressBookIds, 0);
+
+        if (!$addressBookIds) {
+            return $counts;
+        }
+
+        $results = $this->getEntityManager()->getRepository(Card::class)
+            ->createQueryBuilder('c')
+            ->select('IDENTITY(c.addressBook) AS addressBookId, COUNT(c.id) AS count')
+            ->where('c.addressBook IN (:addressBookIds)')
+            ->setParameter('addressBookIds', $addressBookIds)
+            ->groupBy('c.addressBook')
+            ->getQuery()
+            ->getResult();
+
+        foreach ($results as $result) {
+            $counts[(int) $result['addressBookId']] = (int) $result['count'];
+        }
+
+        return $counts;
+    }
+}
diff --git a/src/Repository/CalendarInstanceRepository.php b/src/Repository/CalendarInstanceRepository.php
index 013b4b08..61ac3246 100644
--- a/src/Repository/CalendarInstanceRepository.php
+++ b/src/Repository/CalendarInstanceRepository.php
@@ -23,6 +23,23 @@ public function __construct(ManagerRegistry $registry)
         parent::__construct($registry, CalendarInstance::class);
     }
 
+    /**
+     * Returns every instance the principal has, with its `calendars` row already loaded. Every
+     * caller reads it, so leaving it lazy costs one extra query per calendar.
+     *
+     * @return CalendarInstance[]
+     */
+    public function findByPrincipalUriWithCalendars(string $principalUri): array
+    {
+        return $this->createQueryBuilder('c')
+            ->addSelect('cal')
+            ->join('c.calendar', 'cal')
+            ->where('c.principalUri = :principalUri')
+            ->setParameter('principalUri', $principalUri)
+            ->getQuery()
+            ->getResult();
+    }
+
     /**
      * @return CalendarInstance[] Returns an array of CalendarInstance objects
      */
@@ -118,6 +135,38 @@ public function findAllSchedulingObjectsForCalendar(int $calendarInstanceId, str
             ->getResult();
     }
 
+    /**
+     * Counts the objects of several calendars at once, so that listing a principal's calendars
+     * costs a single query instead of one per calendar.
+     *
+     * @param int[] $calendarIds
+     *
+     * @return array<int, int> count per calendar id, including the calendars that hold nothing
+     */
+    public function countObjectsByCalendar(array $calendarIds): array
+    {
+        $counts = array_fill_keys($calendarIds, 0);
+
+        if (!$calendarIds) {
+            return $counts;
+        }
+
+        $results = $this->getEntityManager()->getRepository(CalendarObject::class)
+            ->createQueryBuilder('o')
+            ->select('IDENTITY(o.calendar) AS calendarId, COUNT(o.id) AS count')
+            ->where('o.calendar IN (:calendarIds)')
+            ->setParameter('calendarIds', $calendarIds)
+            ->groupBy('o.calendar')
+            ->getQuery()
+            ->getResult();
+
+        foreach ($results as $result) {
+            $counts[(int) $result['calendarId']] = (int) $result['count'];
+        }
+
+        return $counts;
+    }
+
     /**
      * Get counts of calendar objects by component type for a calendar instance.
      *
diff --git a/templates/addressbooks/index.html.twig b/templates/addressbooks/index.html.twig
index 3d2ddd80..bdd479b9 100644
--- a/templates/addressbooks/index.html.twig
+++ b/templates/addressbooks/index.html.twig
@@ -23,7 +23,7 @@
             </div>
         </div>
         <p class="mb-1">{{ addressbook.description }}</p>
-        <small>{{ "addressbooks.uri"|trans }} : <code>{{ addressbook.uri }}</code> — {{ "addressbooks.contacts"|trans({'%count%': addressbook.cards|length}) }}</small>
+        <small>{{ "addressbooks.uri"|trans }} : <code>{{ addressbook.uri }}</code> — {{ "addressbooks.contacts"|trans({'%count%': cardCounts[addressbook.id]}) }}</small>
         <div class="btn-group btn-group-sm mt-3 d-flex d-md-none" role="group">
             <a href="{{ path('addressbook_edit',{userId: userId, id: addressbook.id})}}" class="btn btn-sm btn-outline-primary">✎ {{ "edit"|trans }}</a>
             <a href="#"
diff --git a/templates/calendars/index.html.twig b/templates/calendars/index.html.twig
index 822dc5ce..45121fc5 100644
--- a/templates/calendars/index.html.twig
+++ b/templates/calendars/index.html.twig
@@ -45,7 +45,7 @@
             {% if constant('\\App\\Entity\\Calendar::COMPONENT_NOTES') in calendar.calendar.components %}<span class="badge bg-info">{{ "calendars.component.notes"|trans }}</span>{% endif %}
             {% if constant('\\App\\Entity\\Calendar::COMPONENT_TODOS') in calendar.calendar.components %}<span class="badge bg-primary-subtle">{{ "calendars.component.todos"|trans }}</span>{% endif %}
         {% endif %}
-         — {{ "calendars.entries"|trans({'%count%': calendar.calendar.objects|length}) }}
+         — {{ "calendars.entries"|trans({'%count%': compoundObject.objectCount}) }}
         </small>
         <div class="btn-group btn-group-sm mt-3 d-flex d-md-none" role="group">
             {% if not calendar.isPublic() %}
@@ -103,7 +103,7 @@
                 {% if constant('\\App\\Entity\\Calendar::COMPONENT_NOTES') in calendar.calendar.components %}<span class="badge bg-info">{{ "calendars.component.notes"|trans }}</span>{% endif %}
                 {% if constant('\\App\\Entity\\Calendar::COMPONENT_TODOS') in calendar.calendar.components %}<span class="badge bg-primary-subtle">{{ "calendars.component.todos"|trans }}</span>{% endif %}
             {% endif %}
-            — {{ "calendars.entries"|trans({'%count%': calendar.calendar.objects|length}) }}
+            — {{ "calendars.entries"|trans({'%count%': compoundObject.objectCount}) }}
             </small>
             <div class="btn-group btn-group-sm mt-3 d-flex d-md-none" role="group">
                 <a href="{{ path('calendar_edit',{userId: userId, id: calendar.id})}}" class="btn btn-outline-primary">✎ {{ "edit"|trans }}</a>
@@ -147,7 +147,7 @@
                 {% if constant('\\App\\Entity\\Calendar::COMPONENT_NOTES') in calendar.calendar.components %}<span class="badge bg-info">{{ "calendars.component.notes"|trans }}</span>{% endif %}
                 {% if constant('\\App\\Entity\\Calendar::COMPONENT_TODOS') in calendar.calendar.components %}<span class="badge bg-primary-subtle">{{ "calendars.component.todos"|trans }}</span>{% endif %}
             {% endif %}
-            — {{ "calendars.entries"|trans({'%count%': calendar.calendar.objects|length}) }}
+            — {{ "calendars.entries"|trans({'%count%': compoundObject.objectCount}) }}
             </small>
             <div class="btn-group btn-group-sm mt-3 d-flex d-md-none" role="group">
                 <a href="{{ path('calendar_edit',{userId: userId, id: calendar.id})}}" class="btn btn-outline-primary">✎ {{ "edit"|trans }}</a>