diff --git a/net/sockstats/sockstats_tsgo.go b/net/sockstats/sockstats_tsgo.go
index c243b8161..80ff7084a 100644
--- a/net/sockstats/sockstats_tsgo.go
+++ b/net/sockstats/sockstats_tsgo.go
@@ -8,7 +8,6 @@ package sockstats
 import (
 	"context"
 	"fmt"
-	"math"
 	"net"
 	"strings"
 	"sync"
@@ -347,10 +346,12 @@ func (rm *radioMonitor) radioHighPercent() int64 {
 	}
 	periodStart := now - periodLength // start of current reporting period
 
-	// slices of radio usage, with values in chronological order
+	// split into slices of radio usage, with values in chronological order.
+	// split at now+1 so that the current second is in the second slice.
+	split := (now + 1) % radioSampleSize
 	slices := [2][]int64{
-		rm.usage[now%radioSampleSize:],
-		rm.usage[:now%radioSampleSize],
+		rm.usage[split:],
+		rm.usage[:split],
 	}
 	var highPowerSec int64 // total seconds radio was in high power (active or idle)
 	var c int              // counter
@@ -369,5 +370,8 @@ func (rm *radioMonitor) radioHighPercent() int64 {
 		}
 	}
 
-	return int64(math.Round(float64(highPowerSec) / float64(periodLength) * 100))
+	if highPowerSec == 0 {
+		return 0
+	}
+	return highPowerSec * 100 / periodLength
 }
diff --git a/net/sockstats/sockstats_tsgo_test.go b/net/sockstats/sockstats_tsgo_test.go
index 5f4c04d92..f85ab9fca 100644
--- a/net/sockstats/sockstats_tsgo_test.go
+++ b/net/sockstats/sockstats_tsgo_test.go
@@ -39,7 +39,7 @@ func TestRadioMonitor(t *testing.T) {
 				rm.active()
 				tt.Add(10 * time.Second)
 			},
-			50, // radio on 5 seconds of every 10 seconds
+			50, // radio on 5 seconds of 10 seconds
 		},
 		{
 			"400 iterations: 2 sec active, 1 min idle",
@@ -49,11 +49,19 @@ func TestRadioMonitor(t *testing.T) {
 					rm.active()
 					tt.Add(1 * time.Second)
 					rm.active()
-					tt.Add(1 * time.Minute)
+					tt.Add(59 * time.Second)
 				}
 			},
 			10, // radio on 6 seconds of every minute
 		},
+		{
+			"activity at end of time window",
+			func(tt *testTime, rm *radioMonitor) {
+				tt.Add(2 * time.Second)
+				rm.active()
+			},
+			50,
+		},
 	}
 
 	for _, tt := range tests {