Convert 1/2 Inches to MM - Accurate Calculator
Convert 1/2" to millimeters with high precision
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1/2 inch to mm answer
1/2 inch = 12.7 mm exactly.
Exact conversion: 1/2 × 25.4 = 12.7 mm.
Exact formula
Why 25.4 is exact
A half inch is 0.5 inch, so 0.5 × 25.4 = 12.7 mm. The factor 25.4 is exact; rounding only affects optional displayed decimals.
Common approximation and closest metric size
12.7 mm is the exact and standard value. People may say about 13 mm for mental math, but 13 mm is 0.3 mm larger and should not be treated as exact.
Pipe, fittings, and lumber can use nominal sizes. A 1/2 inch label does not always mean the measured part is exactly 12.7 mm.
Where this size is used
Pipe, fittings, and hardware
1/2 inch appears often in fittings, fasteners, and hardware references. Confirm whether the label is nominal or measured before matching metric parts.
Tape measure midpoint and woodworking
Half-inch marks are common layout references. Use 12.7 mm when translating a measured half-inch spacing into metric notes.
Nearby fraction conversions
Nearby fractions give context: 3/8 inch is 9.525 mm, 5/8 inch is 15.875 mm, and 3/4 inch is 19.05 mm.
🔧 DIY & Hardware
For hardware and DIY projects, 1/2" equals 12.70 mm, which is essential when working with metric tools or international specifications.
⚙️ Engineering & Manufacturing
In engineering contexts, 1/2" converts to 12.700000 mm with high precision for accurate technical specifications.
Frequently Asked Questions
How many mm is 1/2 inch?
1/2 inch is 12.7 mm exactly.
Is 1/2 inch the same as 13 mm?
No. 1/2 inch is 12.7 mm. 13 mm is a rough nearby size and is 0.3 mm larger.
What is half an inch in millimeters?
Half an inch equals 12.7 millimeters.
Why can a 1/2 inch pipe be different from 12.7 mm?
Pipe and fitting labels are often nominal trade sizes, so actual inside or outside diameter may differ.
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