Half of 1 5/16 inches is 21/32 inches (0.65625″, 16.67 mm).
How to Calculate It
Convert 1 5/16 to an improper fraction, divide by 2, then simplify. 1 5/16 = 21/16, divided by 2 = 21/32, simplified to 21/32.
On the Tape Measure
The mark at 21/32 inches (0.65625″) is a 1/32-inch mark found on many professional tapes. If your tape does not show 32nds, use the decimal 0.65625 with a digital caliper.
To find half of any tape measure measurement, enter it in TapeMath and tap the Half It button. The result appears instantly on the visual tape.