diff --git a/pkg/workload/util.go b/pkg/workload/util.go
index f19d1d7..c81c769 100644
--- a/pkg/workload/util.go
+++ b/pkg/workload/util.go
@@ -65,6 +65,19 @@ func CalculateExpectedPartition(total *int32, expectedUpdatedReplicas, partition
 	return max(totalReplicas-expectedUpdatedReplicas, 0)
 }
 
+// CalculateProgressingPartition calculates the progressing partition based on the total replicas, expected replicas, and the partition in the spec.
+// In this function, partition means how many replicas need to be updated.
+func CalculateProgressingPartition(total *int32, expectedUpdatedReplicas, partitionInSpec int32) int32 {
+	totalReplicas := ptr.Deref(total, 0)
+
+	if partitionInSpec >= expectedUpdatedReplicas {
+		// already updated if the current updated partition is greater than or equal to the expected updated partition
+		return partitionInSpec
+	}
+
+	return min(expectedUpdatedReplicas, totalReplicas)
+}
+
 // PatchMetadata patches metadata with the given patch
 func PatchMetadata(meta *metav1.ObjectMeta, patch rolloutv1alpha1.MetadataPatch) {
 	if len(patch.Labels) > 0 {
diff --git a/pkg/workload/util_test.go b/pkg/workload/util_test.go
index 91ae3a7..b675427 100644
--- a/pkg/workload/util_test.go
+++ b/pkg/workload/util_test.go
@@ -86,3 +86,64 @@ func TestCalculateExpectedPartition(t *testing.T) {
 		})
 	}
 }
+
+func TestCalculatexProgressingPartition(t *testing.T) {
+	tests := []struct {
+		name             string
+		total            int32
+		expectedReplicas int32
+		partitionInSpec  int32
+		want             int32
+		wantErr          bool
+	}{
+		{
+			name:             "total 10, current partition 0, want to update 1",
+			total:            10,
+			expectedReplicas: 1,
+			partitionInSpec:  0,
+			want:             1,
+			wantErr:          false,
+		},
+		{
+			name:             "total 10, current partition 5, want to update 1",
+			total:            10,
+			expectedReplicas: 1,
+			partitionInSpec:  5,
+			want:             5,
+			wantErr:          false,
+		},
+		{
+			name:             "total 10, current partition 10, want to update 1",
+			total:            10,
+			expectedReplicas: 1,
+			partitionInSpec:  10,
+			want:             10,
+			wantErr:          false,
+		},
+		{
+			name:             "total 10, current partition 15, want to update 0",
+			total:            10,
+			expectedReplicas: 0,
+			partitionInSpec:  15,
+			want:             15,
+			wantErr:          false,
+		},
+		{
+			name:             "total 10, current partition 0, want to update 15",
+			total:            10,
+			expectedReplicas: 15,
+			partitionInSpec:  0,
+			want:             10,
+			wantErr:          false,
+		},
+	}
+	for i := range tests {
+		tt := tests[i]
+		t.Run(tt.name, func(t *testing.T) {
+			got := CalculateProgressingPartition(&tt.total, tt.expectedReplicas, tt.partitionInSpec)
+			if got != tt.want {
+				t.Errorf("CalculateExpectedPartition() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}