Convert 1/4 Inches to MM - Accurate Calculator
Convert 1/4" to millimeters with high precision
Results at Different Precisions
1/4 inch = 6.35 mm exactly.
Exact result
Exact conversion: 1/4 × 25.4 = 6.35 mm.
Approximation
Common approximation: 1/4 inch is normally written as 6.35 mm, not rounded further.
Fit caveat
6 mm is close visually, but it is 0.35 mm smaller than 1/4 inch. That difference can matter for hardware fit, holes, and sheet thickness.
Small hardware and fasteners
Use 6.35 mm when converting quarter-inch spacer thickness, small fasteners, router setup notes, and hardware dimensions.
Plywood and panel notes
Some sheet goods labeled 1/4 inch are nominal and may measure slightly under 6.35 mm, so check the actual measured thickness.
Compare nearby common fractions: 1/8 inch is 3.175 mm, 5/16 inch is 7.9375 mm, and 3/8 inch is 9.525 mm.
🔧 DIY & Hardware
For hardware and DIY projects, 1/4" equals 6.35 mm, which is essential when working with metric tools or international specifications.
⚙️ Engineering & Manufacturing
In engineering contexts, 1/4" converts to 6.350000 mm with high precision for accurate technical specifications.
Frequently Asked Questions
How many mm is 1/4 inch?
1/4 inch is 6.35 mm exactly.
Is 1/4 inch the same as 6 mm?
No. 1/4 inch is 6.35 mm. 6 mm is 0.35 mm smaller, so it is only a rough nearby size.
What is the closest metric size to 1/4 inch?
The exact conversion is 6.35 mm. In rough hardware discussions, 6 mm may be nearby, but it is not exact.
Why is 1/4 inch plywood not always exactly 6.35 mm?
Plywood and sheet goods can use nominal sizes. The label may say 1/4 inch even when the actual measured thickness is slightly different.
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