diff --git a/go.mod b/go.mod
index 475c3a9..3f6fb0b 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,4 @@ module github.com/tklauser/numcpus
 
 go 1.11
 
-require golang.org/x/sys v0.0.0-20210816074244-15123e1e1f71
+require golang.org/x/sys v0.0.0-20220111092808-5a964db01320
diff --git a/go.sum b/go.sum
index a3fe495..7094701 100644
--- a/go.sum
+++ b/go.sum
@@ -1,2 +1,2 @@
-golang.org/x/sys v0.0.0-20210816074244-15123e1e1f71 h1:ikCpsnYR+Ew0vu99XlDp55lGgDJdIMx3f4a18jfse/s=
-golang.org/x/sys v0.0.0-20210816074244-15123e1e1f71/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220111092808-5a964db01320 h1:0jf+tOCoZ3LyutmCOWpVni1chK4VfFLhRsDK7MhqGRY=
+golang.org/x/sys v0.0.0-20220111092808-5a964db01320/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
diff --git a/numcpus.go b/numcpus.go
index e5cc0ce..af59983 100644
--- a/numcpus.go
+++ b/numcpus.go
@@ -1,4 +1,4 @@
-// Copyright 2018 Tobias Klauser
+// Copyright 2018-2022 Tobias Klauser
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -15,8 +15,8 @@
 // Package numcpus provides information about the number of CPUs in the system.
 //
 // It gets the number of CPUs (online, offline, present, possible or kernel
-// maximum) on Linux, Darwin, FreeBSD, NetBSD, OpenBSD, DragonflyBSD or
-// Solaris/Illumos systems.
+// maximum) on Linux, Darwin, FreeBSD, NetBSD, OpenBSD, DragonflyBSD,
+// Solaris/Illumos or Windows systems.
 //
 // On Linux, the information is retrieved by reading the corresponding CPU
 // topology files in /sys/devices/system/cpu.
@@ -24,9 +24,12 @@
 // On BSD systems, the information is retrieved using the hw.ncpu and
 // hw.ncpuonline sysctls, if supported.
 //
+// On Windows systems, the information is retrieved using the
+// GetActiveProcessorCount and GetMaximumProcessorCount functions, respectively.
+//
 // Not all functions are supported on Darwin, FreeBSD, NetBSD, OpenBSD,
-// DragonflyBSD and Solaris/Illumos. ErrNotSupported is returned in case a
-// function is not supported on a particular platform.
+// DragonflyBSD, Solaris/Illumos and Windows. ErrNotSupported is returned in
+// case a function is not supported on a particular platform.
 package numcpus
 
 import "errors"
@@ -42,7 +45,7 @@ func GetConfigured() (int, error) {
 }
 
 // GetKernelMax returns the maximum number of CPUs allowed by the kernel
-// configuration. This function is only supported on Linux systems.
+// configuration. This function is only supported on Linux and Windows systems.
 func GetKernelMax() (int, error) {
 	return getKernelMax()
 }
diff --git a/numcpus_unsupported.go b/numcpus_unsupported.go
index ef79066..4a0b7c4 100644
--- a/numcpus_unsupported.go
+++ b/numcpus_unsupported.go
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build !darwin && !dragonfly && !freebsd && !linux && !netbsd && !openbsd && !solaris
-// +build !darwin,!dragonfly,!freebsd,!linux,!netbsd,!openbsd,!solaris
+//go:build !darwin && !dragonfly && !freebsd && !linux && !netbsd && !openbsd && !solaris && !windows
+// +build !darwin,!dragonfly,!freebsd,!linux,!netbsd,!openbsd,!solaris,!windows
 
 package numcpus
 
diff --git a/numcpus_windows.go b/numcpus_windows.go
new file mode 100644
index 0000000..f7d5b40
--- /dev/null
+++ b/numcpus_windows.go
@@ -0,0 +1,41 @@
+// Copyright 2022 Tobias Klauser
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package numcpus
+
+import "golang.org/x/sys/windows"
+
+func getConfigured() (int, error) {
+	return int(windows.GetActiveProcessorCount(windows.ALL_PROCESSOR_GROUPS)), nil
+}
+
+func getKernelMax() (int, error) {
+	return int(windows.GetMaximumProcessorCount(windows.ALL_PROCESSOR_GROUPS)), nil
+}
+
+func getOffline() (int, error) {
+	return 0, ErrNotSupported
+}
+
+func getOnline() (int, error) {
+	return int(windows.GetActiveProcessorCount(windows.ALL_PROCESSOR_GROUPS)), nil
+}
+
+func getPossible() (int, error) {
+	return int(windows.GetActiveProcessorCount(windows.ALL_PROCESSOR_GROUPS)), nil
+}
+
+func getPresent() (int, error) {
+	return int(windows.GetActiveProcessorCount(windows.ALL_PROCESSOR_GROUPS)), nil
+}