No time for rack space math? Use the Rack Ruler instead. It's a genuinely handy tape measure incremented in both rack spaces (red) and inches (black) down to 1/32? scale. Measuring 1/2? wide by 96? (8 feet) long, its Mylar-coated retracting steel tape is housed in a tough ABS case with a thumb lock and belt clip. This is a rugged tool, not a toy.