diff --git a/prog/weaver/metrics.go b/prog/weaver/metrics.go
index 660a590c..cb47b248 100644
--- a/prog/weaver/metrics.go
+++ b/prog/weaver/metrics.go
@@ -92,6 +92,17 @@ var metrics = []metric{
 			}
 			ch <- intGauge(desc, count)
 		}},
+	{desc("weave_ipam_unreachable_percentage", "Percentage of IP addresses owned  by unreachable peers."),
+		func(s WeaveStatus, desc *prometheus.Desc, ch chan<- prometheus.Metric) {
+			var totalUnreachable uint32
+			for _, entry := range summariseIpamStats(s.IPAM) {
+				if !entry.reachable {
+					totalUnreachable += entry.ips
+				}
+			}
+			percentage := float64(totalUnreachable) * 100.0 / float64(s.IPAM.RangeNumIPs)
+			ch <- prometheus.MustNewConstMetric(desc, prometheus.GaugeValue, percentage)
+		}},
 	{desc("weave_ipam_pending_allocates", "Number of pending allocates."),
 		func(s WeaveStatus, desc *prometheus.Desc, ch chan<- prometheus.Metric) {
 			if s.IPAM != nil {
diff --git a/site/tasks/manage/metrics.md b/site/tasks/manage/metrics.md
index 4d46d779..a2b27371 100644
--- a/site/tasks/manage/metrics.md
+++ b/site/tasks/manage/metrics.md
@@ -21,6 +21,7 @@ exposed:
 * `weave_dns_entries` - Number of DNS entries.
 * `weave_flows` - Number of FastDP flows.
 * `weave_ipam_unreachable_count` - Number of unreachable peers that own IPAM addresses.
+* `weave_ipam_unreachable_percentage` - Percentage of all IP addresses owned by unreachable peers.
 * `weave_ipam_pending_allocates` - Number of pending allocates.
 * `weave_ipam_pending_claims` - Number of pending claims.