diff --git a/app/utils/ceph_calculator.py b/app/utils/ceph_calculator.py
index 7e117fc..78a8352 100644
--- a/app/utils/ceph_calculator.py
+++ b/app/utils/ceph_calculator.py
@@ -60,7 +60,11 @@ def calculate_ceph_capacity(replication_type, replicas=3, k=0, m=0, nodes=None,
     
     # Calculate OSD utilization using the formula x = (s × p) / (s + 1)
     # where s = number of OSDs per server and p = percentage of total utilization
-    osds_per_server = int(nodes[0].get('osd_count', 0)) if nodes else 0
+    # Use the node with the most OSDs for the utilization calculation to avoid
+    # underestimating the usage when nodes differ in size
+    osds_per_server = max(
+        (int(node.get('osd_count', 0)) for node in nodes), default=0
+    ) if nodes else 0
     osd_usage_percent = (osds_per_server * max_recommended_usage_percent) / (osds_per_server + 1)
     
     # Find largest OSD size for calculating capacity after OSD failure