diff --git a/lib/telemetry_ui/backend/ecto_postgres.ex b/lib/telemetry_ui/backend/ecto_postgres.ex
index 2b89cbb..71976f6 100644
--- a/lib/telemetry_ui/backend/ecto_postgres.ex
+++ b/lib/telemetry_ui/backend/ecto_postgres.ex
@@ -42,7 +42,7 @@ defmodule TelemetryUI.Backend.EctoPostgres do
         DO UPDATE SET
           max_value = GREATEST(telemetry_ui_events.max_value, EXCLUDED.value),
           min_value = LEAST(telemetry_ui_events.min_value, EXCLUDED.value),
-          value = ROUND((telemetry_ui_events.value + EXCLUDED.value)::numeric / 2, 4),
+          value = ROUND(((telemetry_ui_events.value * telemetry_ui_events.count) + (EXCLUDED.value * EXCLUDED.count))::numeric / (telemetry_ui_events.count + EXCLUDED.count), 4),
           count = telemetry_ui_events.count + EXCLUDED.count
         """,
         [entry.value, entry.date, entry.name, entry.tags, entry.count, entry.min_value, entry.max_value],
diff --git a/test/telemetry_ui/ecto_postgres_test.exs b/test/telemetry_ui/ecto_postgres_test.exs
index 425af38..32924e9 100644
--- a/test/telemetry_ui/ecto_postgres_test.exs
+++ b/test/telemetry_ui/ecto_postgres_test.exs
@@ -107,7 +107,7 @@ defmodule TelemetryUI.EctoPostgresTest do
 
       [event] = backend.repo.all(Entry)
 
-      assert event.value === 15.0
+      assert event.value === 16.6667
       assert event.tags === %{}
       assert event.count === 6
       assert event.date === ~U[2022-02-10T00:00:00Z]
@@ -136,7 +136,7 @@ defmodule TelemetryUI.EctoPostgresTest do
 
       [event] = backend.repo.all(Entry)
 
-      assert event.value === 15.0
+      assert event.value === 16.6667
       assert event.min_value === 10.0
       assert event.max_value === 20.0
       assert event.tags === %{}