diff --git a/probe/host/reporter.go b/probe/host/reporter.go
index a3d738788..238a4bb84 100644
--- a/probe/host/reporter.go
+++ b/probe/host/reporter.go
@@ -20,7 +20,7 @@ const (
 	Load5         = "load5"
 	Load15        = "load15"
 	CPUUsage      = "cpu_usage_percent"
-	MemUsage      = "mem_usage_percent"
+	MemUsage      = "mem_usage_bytes"
 )
 
 // Exposed for testing.
@@ -76,7 +76,7 @@ func (r *Reporter) Report() (report.Report, error) {
 	metrics := GetLoad(now)
 	cpuUsage, max := GetCPUUsagePercent()
 	metrics[CPUUsage] = report.MakeMetric().Add(now, cpuUsage).WithMax(max)
-	memUsage, max := GetMemoryUsagePercent()
+	memUsage, max := GetMemoryUsageBytes()
 	metrics[MemUsage] = report.MakeMetric().Add(now, memUsage).WithMax(max)
 
 	rep.Host.AddNode(report.MakeHostNodeID(r.hostID), report.MakeNodeWith(map[string]string{
diff --git a/probe/host/reporter_test.go b/probe/host/reporter_test.go
index d5b83be9e..ed6ffd649 100644
--- a/probe/host/reporter_test.go
+++ b/probe/host/reporter_test.go
@@ -38,24 +38,24 @@ func TestReporter(t *testing.T) {
 	defer mtime.NowReset()
 
 	var (
-		oldGetKernelVersion      = host.GetKernelVersion
-		oldGetLoad               = host.GetLoad
-		oldGetUptime             = host.GetUptime
-		oldGetCPUUsagePercent    = host.GetCPUUsagePercent
-		oldGetMemoryUsagePercent = host.GetMemoryUsagePercent
+		oldGetKernelVersion    = host.GetKernelVersion
+		oldGetLoad             = host.GetLoad
+		oldGetUptime           = host.GetUptime
+		oldGetCPUUsagePercent  = host.GetCPUUsagePercent
+		oldGetMemoryUsageBytes = host.GetMemoryUsageBytes
 	)
 	defer func() {
 		host.GetKernelVersion = oldGetKernelVersion
 		host.GetLoad = oldGetLoad
 		host.GetUptime = oldGetUptime
 		host.GetCPUUsagePercent = oldGetCPUUsagePercent
-		host.GetMemoryUsagePercent = oldGetMemoryUsagePercent
+		host.GetMemoryUsageBytes = oldGetMemoryUsageBytes
 	}()
 	host.GetKernelVersion = func() (string, error) { return release + " " + version, nil }
 	host.GetLoad = func(time.Time) report.Metrics { return load }
 	host.GetUptime = func() (time.Duration, error) { return time.ParseDuration(uptime) }
 	host.GetCPUUsagePercent = func() (float64, float64) { return 30.0, 100.0 }
-	host.GetMemoryUsagePercent = func() (float64, float64) { return 60.0, 100.0 }
+	host.GetMemoryUsageBytes = func() (float64, float64) { return 60.0, 100.0 }
 
 	want := report.MakeReport()
 	want.Host.AddNode(report.MakeHostNodeID(hostID), report.MakeNodeWith(map[string]string{
diff --git a/probe/host/system_darwin.go b/probe/host/system_darwin.go
index e0a8278cb..e90528707 100644
--- a/probe/host/system_darwin.go
+++ b/probe/host/system_darwin.go
@@ -89,7 +89,7 @@ var GetCPUUsagePercent = func() (float64, float64) {
 	return 0.0, 0.0
 }
 
-// GetMemoryUsagePercent returns the percent memory usage and max (ie 100)
-var GetMemoryUsagePercent = func() (float64, float64) {
+// GetMemoryUsageBytes returns the bytes memory usage and max
+var GetMemoryUsageBytes = func() (float64, float64) {
 	return 0.0, 0.0
 }
diff --git a/probe/host/system_linux.go b/probe/host/system_linux.go
index 5c1a7846c..f28abb26e 100644
--- a/probe/host/system_linux.go
+++ b/probe/host/system_linux.go
@@ -13,6 +13,8 @@ import (
 	"github.com/weaveworks/scope/report"
 )
 
+const kb = 1024
+
 // Uname is swappable for mocking in tests.
 var Uname = syscall.Uname
 
@@ -102,13 +104,13 @@ var GetCPUUsagePercent = func() (float64, float64) {
 	return float64(totald-idled) * 100. / float64(totald), float64(len(stat.CPUStats)) * 100.
 }
 
-// GetMemoryUsagePercent returns the percent memory usage and max (ie 100)
-var GetMemoryUsagePercent = func() (float64, float64) {
+// GetMemoryUsageBytes returns the bytes memory usage and max
+var GetMemoryUsageBytes = func() (float64, float64) {
 	meminfo, err := linuxproc.ReadMemInfo(ProcMemInfo)
 	if err != nil {
 		return 0.0, 0.0
 	}
 
 	used := meminfo.MemTotal - meminfo.MemFree - meminfo.Buffers - meminfo.Cached
-	return float64(used) * 100. / float64(meminfo.MemTotal), 100.
+	return float64(used * kb), float64(meminfo.MemTotal * kb)
 }