diff --git a/api/internal/state/aggregator.go b/api/internal/state/aggregator.go
index b719c8d..b4447b8 100644
--- a/api/internal/state/aggregator.go
+++ b/api/internal/state/aggregator.go
@@ -76,7 +76,13 @@ type Snapshot struct {
 
 const (
 	maxHistoryPoints = 1440 // 24h at 1 sample/min
-	kvCumulativeWork = "cumulative_shares"
+
+	// kvCumulativeWork is versioned: "cumulative_shares" (v1) accidentally
+	// summed pool.shares (raw per-share count), which is meaningless for
+	// hashrate math. "cumulative_work" (v2) sums pool.accepted — the
+	// diff-1-normalized work, so cumulative_work * 2^32 is real hashes.
+	// The old key is orphaned in the kv table on upgrade; harmless.
+	kvCumulativeWork = "cumulative_work"
 )
 
 // Aggregator refreshes a Snapshot on a ticker.
@@ -285,13 +291,16 @@ func (a *Aggregator) refresh(ctx context.Context) {
 	now := time.Now()
 
 	// --- cumulative work tracking ---
-	// Integrate only positive deltas on pool.Shares. A decrease means
-	// ckpool restarted (or its state reset); reset the baseline without
-	// touching the accumulated total. The first observation after load
-	// only establishes the baseline — those shares were already
-	// accumulated before the previous shutdown.
+	// Integrate only positive deltas on pool.Accepted, which is ckpool's
+	// accounted_diff_shares — the sum of each accepted share's
+	// difficulty, in diff-1-normalized units. pool.Shares is the raw
+	// per-share count and is useless for hashrate math. A decrease
+	// means ckpool restarted (or its state reset); we reset the
+	// baseline without touching the accumulated total. The first
+	// observation after load only establishes the baseline — the
+	// current counter was already integrated before we shut down.
 	if next.Pool != nil {
-		cur := float64(next.Pool.Shares)
+		cur := float64(next.Pool.Accepted)
 		if a.hasPoolSharesBaseline && cur >= a.lastPoolShares {
 			a.cumulativeShares += cur - a.lastPoolShares
 		}
diff --git a/ui/src/lib/PoolOverview.svelte b/ui/src/lib/PoolOverview.svelte
index 7d55f25..82c9aa3 100644
--- a/ui/src/lib/PoolOverview.svelte
+++ b/ui/src/lib/PoolOverview.svelte
@@ -26,11 +26,14 @@
     return expectedBlockSeconds(data.hashrate_hs_1m, data.network_hashrate_hs, diff);
   });
 
-  const effort = $derived.by(() => {
-    if (!isFinite(expected) || expected <= 0) return 0;
-    const uptime = data.uptime_seconds;
-    if (!uptime || uptime <= 0) return 0;
-    return (uptime / expected) * 100;
+  // Round effort: share of the expected work-to-find-a-block that the
+  // pool has already submitted, at the current network difficulty.
+  // Matches ckpool's own accounted_diff_shares / network_diff * 100
+  // (stratifier.c:8201).
+  const roundEffort = $derived.by(() => {
+    const d = data.chain?.difficulty ?? 0;
+    if (!d || d <= 0) return 0;
+    return (data.cumulative_shares / d) * 100;
   });
 
   // Blocks remaining + ETA until the retarget. The predicted adjustment
@@ -121,15 +124,15 @@
   <div class="card">
     <div class="stat-label">Total work</div>
     <div class="stat-value">{formatWork(totalHashes)}</div>
-    <div class="stat-sub">hashes submitted by pool</div>
+    <div class="stat-sub">
+      round effort {roundEffort.toFixed(1)}% of current difficulty
+    </div>
   </div>
 
   <div class="card">
     <div class="stat-label">Expected block</div>
     <div class="stat-value">{formatDuration(expected)}</div>
-    <div class="stat-sub">
-      effort {effort.toFixed(1)}% · uptime {formatUptime(data.uptime_seconds)}
-    </div>
+    <div class="stat-sub">uptime {formatUptime(data.uptime_seconds)}</div>
   </div>
 
   <div class="card">