Inches to MM Conversion Chart
Generate and print custom inches to millimeters conversion charts. Support for both decimal and fractional inches with adjustable precision.
Chart Settings
Chart Preview: 0" to 12", step 0.5" • 25 rows
Chart Preview
How to use this inches to mm chart
Use this inches to mm chart when a plan, ruler, product listing, or classroom problem starts with inches and needs millimeters. The math is exact: millimeters = inches × 25.4. Decimal inch rows are useful for product dimensions and engineering notes, while fractional rows match common tape-measure marks.
Common fraction values
Popular ruler fractions include 1/4 inch = 6.35 mm, 5/16 inch = 7.9375 mm, 3/8 inch = 9.525 mm, 1/2 inch = 12.7 mm, and 7/8 inch = 22.225 mm.
Closest metric size caution
Nearby rounded metric sizes are convenient for quick checks, but they are not always substitutes. For hardware, drill bits, sockets, or tolerance-sensitive work, use the exact value or verify the specification.
When decimal inches are better
Decimal inch inputs such as 0.5, 1.25, or 2.75 produce clean millimeter values for CAD notes, product listings, packaging dimensions, and lab or manufacturing documentation.
Recommended chart ranges
Use 0–12 inches for most ruler and lumber references. Use 0–48 inches or 0–96 inches for sheet goods, large boards, and construction materials.
How to read fractional inches in the chart
Exact conversion first, rounding second
For fractional inch values, the chart is most useful when you need to compare exact millimeter results with familiar ruler marks. Use the exact value for specifications, then round only after deciding whether the measurement is for a drawing, a classroom problem, or a rough shop reference.
A rounded metric number can be convenient, but it should not replace the original fraction automatically. For example, 3/8 inch is 9.525 mm, so a 10 mm part is larger. A quarter inch is 6.35 mm, so 6 mm is smaller. Those differences may matter for holes, dowels, panels, fasteners, sockets, and replacement parts.
Use chart ranges that match your material
A short ruler chart is enough for craft pieces, model parts, and small hardware. Longer ranges are better for sheet goods, lumber, product dimensions, packaging, and construction notes. If you are preparing a worksheet, mix easy exact values such as 1 inch = 25.4 mm with common fractions so students practice both decimal and fractional thinking.
When copying chart values, keep units visible on every row or table heading. A clear label such as inches, fraction, and millimeters prevents readers from confusing input values with converted results, especially when decimal inches and fractional inches appear together.
Popular fractional inch conversions
These common tape-measure fractions convert to exact millimeter values using 25.4 mm per inch.
Related printable charts
Need more workshop, automotive, or measurement references? These printable chart resources pair well with this inches to mm chart.
Decimal & Fractions
Generate charts with decimal inches (2.5") or common fractions (1/2", 3/8", 5/16") for traditional measurements.
Flexible Ranges
Create charts from 0 to 200 inches with customizable intervals. Perfect for any project size.
Print Optimized
Clean, professional layout designed for printing. Save as PDF or print directly for reference.
Common Use Cases
🪵 Woodworking & Carpentry
Essential for woodworkers using imperial measurements who need metric equivalents for international plans or tools.
🔩 Hardware & Fasteners
Quick reference for bolt sizes, drill bits, and hardware when working with mixed measurement systems.
🏗️ Construction
Convert standard imperial building dimensions to metric for international projects or specifications.
🛠️ Manufacturing
Critical for manufacturing environments working with both imperial and metric tolerances and specifications.
Frequently Asked Questions
What is the formula behind the inches to mm chart?
The chart uses millimeters = inches × 25.4.
Should I use decimal or fractional inches?
Use decimal inches for precision work and engineering. Use fractional inches such as 1/2 inch or 3/8 inch when you are reading a tape measure or ruler.
What fraction precision should I choose?
For most woodworking and DIY, 1/16 inch is standard. For fine woodworking or precision work, use 1/32 inch. For rough framing, 1/8 inch may be enough.
Can I print this inches to mm chart?
Yes. Click Print Chart to open a print-friendly view, then print directly or save as PDF from your browser print dialog.
Need Quick Conversions?
Use our interactive converter for instant conversions without creating a full chart.
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