diff --git a/length.go b/length.go
index be87f62..24f1328 100644
--- a/length.go
+++ b/length.go
@@ -48,6 +48,7 @@ const (
 	// space
 	LunarDistance    = Kilometer * 384400
 	AstronomicalUnit = Meter * 149597870700
+	LightYear        = Meter * 9460730472580800
 )
 
 // Yoctometers returns the length in ym
@@ -229,3 +230,8 @@ func (l Length) LunarDistances() float64 {
 func (l Length) AstronomicalUnits() float64 {
 	return float64(l / AstronomicalUnit)
 }
+
+// LightYears returns the length in ly
+func (l Length) LightYears() float64 {
+	return float64(l / LightYear)
+}
diff --git a/length_test.go b/length_test.go
index 04f9aa6..e7da227 100644
--- a/length_test.go
+++ b/length_test.go
@@ -58,4 +58,5 @@ func TestLength(t *testing.T) {
 	// space
 	assert.Equal(t, 389.17240036420395, (1 * AstronomicalUnit).LunarDistances())
 	assert.Equal(t, 0.0025695552897999903, (1 * LunarDistance).AstronomicalUnits())
+	assert.Equal(t, 63241.07708426628, (1 * LightYear).AstronomicalUnits())
 }