diff --git a/go/src/infra/fleetconsole/internal/consoleserver/count_browser_devices.go b/go/src/infra/fleetconsole/internal/consoleserver/count_browser_devices.go
index c3b8ce6..6e582ce 100644
--- a/go/src/infra/fleetconsole/internal/consoleserver/count_browser_devices.go
+++ b/go/src/infra/fleetconsole/internal/consoleserver/count_browser_devices.go
@@ -8,16 +8,15 @@
 	"context"
 
 	"go.chromium.org/infra/fleetconsole/api/fleetconsolerpc"
+	browserdevicedb "go.chromium.org/infra/fleetconsole/internal/database/browser_devicedb"
+	"go.chromium.org/infra/fleetconsole/internal/ufsclient"
 )
 
 func (frontend *FleetConsoleFrontend) CountBrowserDevices(ctx context.Context, req *fleetconsolerpc.CountBrowserDevicesRequest) (_ *fleetconsolerpc.CountBrowserDevicesResponse, err error) {
-	return &fleetconsolerpc.CountBrowserDevicesResponse{
-		Total: 21345,
-		SwarmingState: &fleetconsolerpc.SwarmingStateCounts{
-			Alive:       16930,
-			Dead:        417,
-			Quarantined: 372,
-			Maintenance: 18,
-		},
-	}, nil
+	realms, err := ufsclient.GetUserRealms(ctx, frontend.cloudProject)
+	if err != nil {
+		return nil, err
+	}
+
+	return browserdevicedb.CountDevices(ctx, req.GetFilter(), realms)
 }
diff --git a/go/src/infra/fleetconsole/internal/database/browser_devicedb/count_devices.go b/go/src/infra/fleetconsole/internal/database/browser_devicedb/count_devices.go
new file mode 100644
index 0000000..f0c8cbe
--- /dev/null
+++ b/go/src/infra/fleetconsole/internal/database/browser_devicedb/count_devices.go
@@ -0,0 +1,81 @@
+// Copyright 2026 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package browserdevicedb
+
+import (
+	"context"
+
+	"entgo.io/ent/dialect/sql/sqljson"
+
+	"go.chromium.org/luci/common/errors"
+
+	"go.chromium.org/infra/fleetconsole/api/fleetconsolerpc"
+	"go.chromium.org/infra/fleetconsole/internal/database"
+	"go.chromium.org/infra/fleetconsole/internal/database/queryutils"
+	"go.chromium.org/infra/fleetconsole/internal/ent/entx"
+	ent "go.chromium.org/infra/fleetconsole/internal/ent/generated"
+	"go.chromium.org/infra/fleetconsole/internal/ent/generated/browserdevice"
+	"go.chromium.org/infra/fleetconsole/internal/ent/generated/migrate"
+	"go.chromium.org/infra/fleetconsole/internal/ent/generated/predicate"
+	"go.chromium.org/infra/fleetconsole/internal/swarmingclient"
+)
+
+type DeviceCounts struct {
+	Total       int32 `sql:"total"`
+	Alive       int32 `sql:"alive"`
+	Dead        int32 `sql:"dead"`
+	Quarantined int32 `sql:"quarantined"`
+	Maintenance int32 `sql:"maintenance"`
+}
+
+// CountDevices calculates browser devices related metrics.
+func CountDevices(ctx context.Context, filter string, realms []string) (*fleetconsolerpc.CountBrowserDevicesResponse, error) {
+	var rows []DeviceCounts
+	client := database.GetEntClient(ctx)
+
+	p, err := queryutils.ToEntPredicate(filter, migrate.BrowserDevicesTable)
+	if err != nil {
+		return nil, errors.Fmt("failed to parse filter: %w", err)
+	}
+
+	q := client.BrowserDevice.Query().Where(p)
+
+	if realms != nil {
+		realmChecks := []predicate.BrowserDevice{browserdevice.RealmIsNil()}
+		if len(realms) > 0 {
+			realmChecks = append(realmChecks, browserdevice.RealmIn(realms...))
+		}
+		q.Where(browserdevice.Or(realmChecks...))
+	}
+
+	jsonPath := sqljson.Path("state")
+	err = q.
+		Aggregate(
+			ent.As(ent.Count(), "total"),
+			ent.As(entx.CountIf(sqljson.ValueContains(browserdevice.FieldSwarmingLabels, string(swarmingclient.Alive), jsonPath)), string(swarmingclient.Alive)),
+			ent.As(entx.CountIf(sqljson.ValueContains(browserdevice.FieldSwarmingLabels, string(swarmingclient.Dead), jsonPath)), string(swarmingclient.Dead)),
+			ent.As(entx.CountIf(sqljson.ValueContains(browserdevice.FieldSwarmingLabels, string(swarmingclient.Quarantined), jsonPath)), string(swarmingclient.Quarantined)),
+			ent.As(entx.CountIf(sqljson.ValueContains(browserdevice.FieldSwarmingLabels, string(swarmingclient.Maintenance), jsonPath)), string(swarmingclient.Maintenance))).
+		Scan(ctx, &rows)
+
+	if err != nil {
+		return nil, err
+	}
+
+	if len(rows) == 0 {
+		return &fleetconsolerpc.CountBrowserDevicesResponse{}, nil
+	}
+
+	result := rows[0]
+	return &fleetconsolerpc.CountBrowserDevicesResponse{
+		Total: result.Total,
+		SwarmingState: &fleetconsolerpc.SwarmingStateCounts{
+			Alive:       result.Alive,
+			Dead:        result.Dead,
+			Quarantined: result.Quarantined,
+			Maintenance: result.Maintenance,
+		},
+	}, nil
+}
diff --git a/go/src/infra/fleetconsole/internal/database/browser_devicedb/count_devices_test.go b/go/src/infra/fleetconsole/internal/database/browser_devicedb/count_devices_test.go
new file mode 100644
index 0000000..b03cbd3
--- /dev/null
+++ b/go/src/infra/fleetconsole/internal/database/browser_devicedb/count_devices_test.go
@@ -0,0 +1,91 @@
+// Copyright 2026 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package browserdevicedb
+
+import (
+	"context"
+	"database/sql/driver"
+	"regexp"
+	"testing"
+
+	"github.com/DATA-DOG/go-sqlmock"
+
+	"go.chromium.org/luci/common/testing/truth/assert"
+	"go.chromium.org/luci/common/testing/truth/should"
+	"go.chromium.org/luci/server/sqldb"
+
+	"go.chromium.org/infra/fleetconsole/api/fleetconsolerpc"
+)
+
+func TestCountDevicesSQL(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name               string
+		filter             string
+		realms             []string
+		expectedSQL        string
+		expectedParameters []driver.Value
+	}{
+		{
+			name:   "no filter, no realms",
+			filter: "",
+			realms: nil,
+			expectedSQL: `SELECT COUNT(*) AS "total", ` +
+				`COUNT(*) FILTER (WHERE ("swarming_labels"->'state')::jsonb @> $1) AS "alive", ` +
+				`COUNT(*) FILTER (WHERE ("swarming_labels"->'state')::jsonb @> $2) AS "dead", ` +
+				`COUNT(*) FILTER (WHERE ("swarming_labels"->'state')::jsonb @> $3) AS "quarantined", ` +
+				`COUNT(*) FILTER (WHERE ("swarming_labels"->'state')::jsonb @> $4) AS "maintenance" ` +
+				`FROM "browser_devices"`,
+			expectedParameters: []driver.Value{`"alive"`, `"dead"`, `"quarantined"`, `"maintenance"`},
+		},
+		{
+			name:   "with filter, with realms",
+			filter: "id = 'device1'",
+			realms: []string{"realm1"},
+			expectedSQL: `SELECT COUNT(*) AS "total", ` +
+				`COUNT(*) FILTER (WHERE ("swarming_labels"->'state')::jsonb @> $1) AS "alive", ` +
+				`COUNT(*) FILTER (WHERE ("swarming_labels"->'state')::jsonb @> $2) AS "dead", ` +
+				`COUNT(*) FILTER (WHERE ("swarming_labels"->'state')::jsonb @> $3) AS "quarantined", ` +
+				`COUNT(*) FILTER (WHERE ("swarming_labels"->'state')::jsonb @> $4) AS "maintenance" ` +
+				`FROM "browser_devices" ` +
+				`WHERE "id" = $5 AND ("browser_devices"."realm" IS NULL OR "browser_devices"."realm" IN ($6))`,
+			expectedParameters: []driver.Value{`"alive"`, `"dead"`, `"quarantined"`, `"maintenance"`, "'device1'", "realm1"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ctx := context.Background()
+			db, mock, err := sqlmock.New()
+			if err != nil {
+				t.Fatalf("an error '%q' was not expected when opening a stub database connection", err)
+			}
+			defer db.Close()
+			ctx = sqldb.UseDB(ctx, db)
+
+			mock.ExpectQuery(regexp.QuoteMeta(tt.expectedSQL)).
+				WithArgs(tt.expectedParameters...).
+				WillReturnRows(sqlmock.NewRows([]string{"total", "alive", "dead", "quarantined", "maintenance"}).
+					AddRow(10, 5, 2, 1, 2))
+
+			res, err := CountDevices(ctx, tt.filter, tt.realms)
+			assert.NoErr(t, err)
+			assert.Loosely(t, res, should.Match(&fleetconsolerpc.CountBrowserDevicesResponse{
+				Total: 10,
+				SwarmingState: &fleetconsolerpc.SwarmingStateCounts{
+					Alive:       5,
+					Dead:        2,
+					Quarantined: 1,
+					Maintenance: 2,
+				},
+			}))
+
+			if err := mock.ExpectationsWereMet(); err != nil {
+				t.Errorf("there were unfulfilled expectations: %s", err)
+			}
+		})
+	}
+}
diff --git a/go/src/infra/fleetconsole/internal/ent/entx/builder.go b/go/src/infra/fleetconsole/internal/ent/entx/builder.go
index 9b619005..b677632 100644
--- a/go/src/infra/fleetconsole/internal/ent/entx/builder.go
+++ b/go/src/infra/fleetconsole/internal/ent/entx/builder.go
@@ -7,7 +7,10 @@
 import (
 	"fmt"
 
+	"entgo.io/ent/dialect"
 	"entgo.io/ent/dialect/sql"
+
+	ent "go.chromium.org/infra/fleetconsole/internal/ent/generated"
 )
 
 // True returns a standard SQL TRUE predicate.
@@ -32,3 +35,31 @@
 func Lateral(name string) *sql.SelectTable {
 	return sql.Table(fmt.Sprintf("LATERAL %s", name))
 }
+
+// CountIf generates COUNT(*) FILTER (WHERE <predicate>) or
+// COUNT(CASE WHEN <predicate> THEN 1 END) depending on the dialect.
+func CountIf(p *sql.Predicate) ent.AggregateFunc {
+	return func(s *sql.Selector) string {
+		// Sync the predicate's internal builder with the main query.
+		// We set Total() so the predicate generates placeholders ($5, $6)
+		// that continue from where the main query left off.
+		p.SetDialect(s.Dialect())
+		p.SetTotal(s.Total())
+
+		// Compile the predicate to SQL and arguments.
+		condition, args := p.Query()
+
+		// Inject the arguments into the main query.
+		// We use sql.Expr("", args...) to trick the builder into appending
+		// the arguments to its internal slice WITHOUT writing any new SQL
+		// text to the buffer (because the expr string is empty).
+		s.Arg(sql.Expr("", args...))
+
+		if s.Dialect() == dialect.Postgres {
+			// Return the standard Postgres aggregation SQL.
+			return fmt.Sprintf("COUNT(*) FILTER (WHERE %s)", condition)
+		}
+
+		return fmt.Sprintf("COUNT(CASE WHEN %s THEN 1 END)", condition)
+	}
+}