diff --git a/netutil/netspeed.go b/netutil/netspeed.go
index d9b1a2b..927b05a 100644
--- a/netutil/netspeed.go
+++ b/netutil/netspeed.go
@@ -49,7 +49,7 @@ func (n *NetSpeedReader) Read() ([]NetSpeed, error) {
 		return nil, err
 	}
 	sMap := convertToDevStatusMapWithFilter(s, n.targetDevs)
-	speedList := cal(sMap, ls, int((t.UnixNano()-lt.UnixNano())/1000))
+	speedList := cal(sMap, ls, int((t.UnixNano()-lt.UnixNano())/1000000))
 	n.recordTime = t
 	n.statusMap = sMap
 	return speedList, nil
diff --git a/netutil/netspeed_test.go b/netutil/netspeed_test.go
new file mode 100644
index 0000000..a4aeb10
--- /dev/null
+++ b/netutil/netspeed_test.go
@@ -0,0 +1,45 @@
+package netutil
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCal(t *testing.T) {
+	s1, err := ReadDevStatus(func(p string) (string, error) {
+		return data1, nil
+	})
+	assert.NoError(t, err)
+	s2, err := ReadDevStatus(func(p string) (string, error) {
+		return data2, nil
+	})
+	assert.NoError(t, err)
+	map1 := convertToDevStatusMap(s1)
+	map2 := convertToDevStatusMap(s2)
+	speeds := cal(map1, map2, 1000)
+	assert.Equal(t, len(speeds), 3)
+	var speed NetSpeed
+	for _, ss := range speeds {
+		if ss.DevName == "br-lan" {
+			speed = ss
+		}
+	}
+	assert.Equal(t, speed.DevName, "br-lan")
+	assert.Equal(t, speed.ReceiveSpeed, uint64(1000))
+	assert.Equal(t, speed.TransmitSpeed, uint64(2000))
+}
+
+const data1 = `Inter-|   Receive                                                |  Transmit
+ face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
+br-lan: 88232992879 78760799    0    0    0     0          0         0 99798877563 67202989    0    0    0     0       0          0
+ wlan0:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
+    lo: 2312260588 3252792    0    0    0     0          0         0 2312260588 3252792    0    0    0     0       0          0
+`
+
+const data2 = `Inter-|   Receive                                                |  Transmit
+ face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
+br-lan: 88232993879 78760799    0    0    0     0          0         0 99798879563 67202989    0    0    0     0       0          0
+ wlan0:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
+    lo: 2312260588 3252792    0    0    0     0          0         0 2312260588 3252792    0    0    0     0       0          0
+`