diff --git a/docker/client.go b/docker/client.go
index 63d0fea4..899cf02a 100644
--- a/docker/client.go
+++ b/docker/client.go
@@ -138,14 +138,20 @@ func (d *dockerClient) ContainerStats(ctx context.Context, id string, stats chan
 				log.Errorf("decoder for stats api returned an unknown error %v", err)
 			}
 
+			ncpus := uint8(v.CPUStats.OnlineCPUs)
+			if ncpus == 0 {
+				ncpus = uint8(len(v.CPUStats.CPUUsage.PercpuUsage))
+			}
+
 			var (
 				cpuDelta    = float64(v.CPUStats.CPUUsage.TotalUsage) - float64(v.PreCPUStats.CPUUsage.TotalUsage)
 				systemDelta = float64(v.CPUStats.SystemUsage) - float64(v.PreCPUStats.SystemUsage)
-				cpuPercent  = int64((cpuDelta / systemDelta) * float64(len(v.CPUStats.CPUUsage.PercpuUsage)) * 100)
+				cpuPercent  = int64((cpuDelta / systemDelta) * float64(ncpus) * 100)
 				memUsage    = int64(v.MemoryStats.Usage - v.MemoryStats.Stats["cache"])
 				memPercent  = int64(float64(memUsage) / float64(v.MemoryStats.Limit) * 100)
 			)
 
+
 			if cpuPercent > 0 || memUsage > 0 {
 				select {
 				case <-ctx.Done():