diff -r 6310a0f98734 src/strings.cpp
--- a/src/strings.cpp	Sun Feb 26 18:46:36 2012 +0000
+++ b/src/strings.cpp	Mon Feb 27 03:58:35 2012 -0700
@@ -689,7 +689,9 @@
  */
 uint ConvertKmhishSpeedToDisplaySpeed(uint speed)
 {
-	return _units[_settings_game.locale.units].c_velocity.ToDisplay(speed * 10, false) / 16;
+	const uint64 A = 16 * (1 << _units[_settings_game.locale.units].c_velocity.shift);
+	const uint64 B = 10 * _units[_settings_game.locale.units].c_velocity.multiplier;
+	return speed * B / A;  // Rounds down
 }
 
 /**
@@ -699,7 +701,9 @@
  */
 uint ConvertDisplaySpeedToKmhishSpeed(uint speed)
 {
-	return _units[_settings_game.locale.units].c_velocity.FromDisplay(speed * 16) / 10;
+	const uint64 A = 16 * (1 << _units[_settings_game.locale.units].c_velocity.shift);
+	const uint64 B = 10 * _units[_settings_game.locale.units].c_velocity.multiplier;
+	return (speed * A + B-1) / B;  // Rounds up
 }
 /**
  * Parse most format codes within a string and write the result to a buffer.