Inches to MM Conversion Chart(Printable & Professional Guide)

The essential reference for 3D printing, international manufacturing, and mechanical engineering. Convert fractional inches like 1/2", 1/4", or 1/8" to exact millimeter values instantly.

Maker Ready - 3D Print Verified
Exact - 25.4 Standard
Free PDF - Instant Access
3/3 free downloads today
Quick Presets:

Preview & Download

3D Printing 0-6"

ChartsPrintables.com

Inches to MM Conversion Chart

Range: 0-6" • Step: 0.125" • Precision: 1 decimal

Inches (Fraction)Inches (Decimal)Millimeters (mm)
0"0.0000"0 mm
1/8"0.1250"3.2 mm
1/4"0.2500"6.3 mm
3/8"0.3750"9.5 mm
1/2"0.5000"12.7 mm
5/8"0.6250"15.9 mm
3/4"0.7500"19 mm
7/8"0.8750"22.2 mm
1"1.0000"25.4 mm
1 1/8"1.1250"28.6 mm
1 1/4"1.2500"31.8 mm
1 3/8"1.3750"34.9 mm
1 1/2"1.5000"38.1 mm
1 5/8"1.6250"41.3 mm
1 3/4"1.7500"44.4 mm
1 7/8"1.8750"47.6 mm
2"2.0000"50.8 mm
2 1/8"2.1250"54 mm
2 1/4"2.2500"57.1 mm
2 3/8"2.3750"60.3 mm
2 1/2"2.5000"63.5 mm
2 5/8"2.6250"66.7 mm
2 3/4"2.7500"69.8 mm
2 7/8"2.8750"73 mm
3"3.0000"76.2 mm
3 1/8"3.1250"79.4 mm
3 1/4"3.2500"82.5 mm
3 3/8"3.3750"85.7 mm
3 1/2"3.5000"88.9 mm
3 5/8"3.6250"92.1 mm
3 3/4"3.7500"95.3 mm
3 7/8"3.8750"98.4 mm
4"4.0000"101.6 mm
4 1/8"4.1250"104.8 mm
4 1/4"4.2500"107.9 mm
4 3/8"4.3750"111.1 mm
4 1/2"4.5000"114.3 mm
4 5/8"4.6250"117.5 mm
4 3/4"4.7500"120.6 mm
4 7/8"4.8750"123.8 mm
5"5.0000"127 mm
5 1/8"5.1250"130.2 mm
5 1/4"5.2500"133.3 mm
5 3/8"5.3750"136.5 mm
5 1/2"5.5000"139.7 mm
5 5/8"5.6250"142.9 mm
5 3/4"5.7500"146 mm
5 7/8"5.8750"149.2 mm
6"6.0000"152.4 mm

Formula: mm = inches × 25.4

Generated by ChartsPrintables.com • Free to use and share

File Details

Rows

49

Range

0-6"

PDF FILE SIZE

0KB

Quality

300 DPI

Fixing the "25.4x" Scaling Error in 3D Printing

Did your 1-inch model import as tiny as a grain of rice? You likely hit the classic unit trap.

Common Nozzle Matches

  • 0.4mm Nozzle ≈ 0.0157"
  • 0.6mm Nozzle ≈ 0.0236"
  • 0.8mm Nozzle ≈ 0.0315"

Pro Tip for Slicers

If your slicer (Cura, Bambu Studio) defaults to mm but your STL was exported in inches, scale the model by 2540% to restore its original size. Always use our chart to verify critical clearances for hardware.

Warning: Nominal Pipe Sizes Are Not Actual

In plumbing and industrial gas lines, "inches" refer to flow capacity, not outer diameter.

Nominal SizeActual OD (Inch)Actual OD (MM)
1/2" Pipe0.840"21.34mm
3/4" Pipe1.050"26.67mm
1" Pipe1.315"33.40mm

Imperial to Metric Bolt Substitutes

Can you use a metric nut on an imperial bolt? Use this safety guide.

Closest Inch-to-MM Matches

  • 1/4" Bolt 6.35mm (M6 is loose)
  • 5/16" Bolt 7.94mm (M8 is perfect)
  • 1/2" Bolt 12.70mm (M13 is close)
  • 3/4" Bolt 19.05mm (M19 is perfect)
Note: Even if diameters are close, thread pitches (TPI vs mm pitch) are almost always different. Never mix fasteners in structural or engine applications.

Effective Inch-to-MM Conversion

Master technical measurements with our professional guide.

Fractional Reading

Supports 1/2, 1/4, 1/8, and 1/16 increments common in US blueprints and architectural drawings.

Precision Levels

Choose up to 4 decimal places for millimeter results, essential for CNC machining and engineering.

Print Settings

Always print at 100% scale on US Letter paper for workshop use. We recommend high-gsm paper.

Where Precision Matters

📐

CAD Design

Convert US architectural dimensions to metric for international manufacturing projects.

🔌

Electronics

Match imperial component leads (0.1" spacing) to metric PCB mounting hole grids.

🏎️

Automotive

Upgrade vintage US car parts with modern metric hardware without clearance issues.

The Math: How to Convert Inches to MM

Core Formula

MM = Inches × 25.4

The factor 25.4 is the international standard defined in 1959. It is an exact number, ensuring infinite precision in your workshop conversions.

Choosing the Right Chart

Use Inches-to-MM if:

  • • You have an American blueprint
  • • You are scaling 3D models
  • • You use US standard drill bits

Use MM-to-Inches if:

  • • You have a metric tool set
  • • You are assembling IKEA furniture
  • • You use digital calipers in mm

Related Technical Charts

Complete your garage reference wall with these printable guides.

CM → InchesSizing helper
CentimetersMetersDecimal (in)Fraction (in)ft'-in
50.051.971 15/16"0'2"
100.103.943 15/16"0'4"
200.207.877 7/8"0'8"
300.3011.8111 13/16"1'0"
500.5019.6919 11/16"1'8"
700.7027.5627 9/16"2'4"
900.9035.4335 7/16"2'11"
1001.0039.3739 3/8"3'3"
1301.3051.1851 3/16"4'3"
1801.8070.8770 7/8"5'11"

CM to Inches Chart

Convert centimeters to inches with precision for international sizing and measurements.

Customize & Download

Frequently Asked Questions

How many mm are in 1/4 inch?
1/4 inch is exactly 6.35 millimeters.
Is 1 inch exactly 25.4mm?
Yes. Since 1959, the international inch is defined as precisely 25.4mm. There is no rounding error in this conversion.
What is 0.001 inch in mm?
0.001 inch (known as 1 'thou') is exactly 0.0254 millimeters. This is a critical unit in precision machining.
Why did my 3D print import 25.4x too small?
This happens when your CAD software (Fusion 360, etc.) exports in inches but your slicer (Cura, Bambu Studio) defaults to millimeters. Simply scale the model by 2540% to fix it.
What is 1/16 inch in mm?
1/16 inch is exactly 1.5875 millimeters. This is the smallest common increment on standard US tape measures.
Is 5mm the same as 3/16 inch?
No. 3/16 inch is 4.76mm. While they are close, using a 3/16" bit for a 5mm hole will result in a tight, impossible fit for most hardware.