"half the width of" is correct and usable in written English.
You can use it to compare the width of two things. For example, "The bridge was half the width of the nearby river."
Many of its keys (including, alas, the period and the comma) are mere slivers, half the width of normal keys.
Along one dirt road, a grower took up half the width of the road itself to dry his leaves.
A trench, 4 feet long and 2 feet deep, had been dug in advance, taking up half the width of the main street.
"It's hypnotic," said Mr. Almereyda, a New Yorker whose favorite part of the camera is the tiny plastic lens, which is half the width of a pencil eraser.
"Remember that before 1967, Israel was all of nine miles wide; it's half the width of the Washington Beltway," Mr. Netanyahu said.
Forty years later, we receive instead a $1,200 coach seat half the width of a human pelvis, a mismatched pair of circus peanuts and the in-flight director's recut of "Bicentennial Man".
In Venice, the razor clams are half the width of those sold here, sometimes no longer than three inches, and served grilled on the half shell with a gloss of butter.
LIGO's two detectors -- one in Hanford, Wash., the other in Livingston, La .-- will be able to spot a change as slight as half the width of an atom along the 2.5-mile-long paths traveled by the detectors' laser beams.
This deviation in dimension is equal to the half the width of the cut.
