diff --git a/py/hexagram/dial.py b/py/hexagram/dial.py
index 311dc1f..4c76584 100644
--- a/py/hexagram/dial.py
+++ b/py/hexagram/dial.py
@@ -3,6 +3,8 @@ import cairo
 
 from hexagram.gauge import Gauge
 
+RAD = math.pi / 180.0
+
 class Dial(Gauge):
     __slots = 'x', 'y', 'radius', 'min_angle', 'max_angle',
 
@@ -113,7 +115,7 @@ class Dial(Gauge):
         cr.set_source(gradient)
 
         cr.arc(self.x, self.y, self.radius * 0.713,
-               self.min_angle - self.ANGLE_OFFSET - (math.pi / 180.0) * 1.5,
+               self.min_angle - self.ANGLE_OFFSET - RAD * 1.5,
                angle)
 
         cr.stroke()
@@ -121,8 +123,8 @@ class Dial(Gauge):
         self.draw_needle(cr, 0.5, 0.89, angle)
 
 class BottomDial(Dial):
-    MIN_ANGLE = 144.0 * (math.pi / 180.0)
-    MAX_ANGLE = 216.0 * (math.pi / 180.0)
+    MIN_ANGLE = 144.0 * RAD
+    MAX_ANGLE = 216.0 * RAD
 
     def angle(self, value: float):
         return super().angle((self.max_value - value) + self.min_value)
@@ -142,8 +144,8 @@ class BottomDial(Dial):
         cr.arc(self.x,
                self.y,
                self.radius - 36,
-               self.MIN_ANGLE - self.ANGLE_OFFSET - 4 * (math.pi / 180.0),
-               self.MAX_ANGLE - self.ANGLE_OFFSET + 4 * (math.pi / 180.0))
+               self.MIN_ANGLE - self.ANGLE_OFFSET - 4 * RAD,
+               self.MAX_ANGLE - self.ANGLE_OFFSET + 4 * RAD)
         cr.stroke()
 
     def draw_fg(self, cr: cairo.Context):