Millimeters to Inches Converter

How to use this calculator

1. Enter the measurement in millimeters.
2. We divide by 25.4 to convert to inches.
3. Use the inch value in US-based plans or shopping lists.

Inputs explained

Millimeters

Length in millimeters. Decimals welcome for precise parts; convert from cm by multiplying by 10 first.

When to use it

• Checking imported hardware dimensions against imperial designs.
• Preparing shop drawings or cut lists in inches when the source is metric.
• Comparing metric 3D print models to imperial build volume constraints.
• Converting metric spec sheets into inch-based part catalogs.
• Translating metric furniture dimensions into inches for US shoppers.

Tips & cautions

• Translate decimal inches into the nearest fraction (e.g., 0.375 = 3/8) if your tools prefer fractions.
• Match rounding to your tolerance—tight fits may need four decimals.
• Verify conversions both directions if you’re machining critical components.
• Be careful not to confuse mm with cm—1 cm = 10 mm. Always convert to mm first before using this tool.
• For bolt and screw diameters, compare converted inches to standard imperial sizes (e.g., 1/4", 3/8").
• Outputs decimal inches only; fractional formatting is manual.
• Assumes positive measurements.
• Rounding may differ from your CAD or CAM precision settings.
• Does not snap to standard imperial lumber sizes or hardware increments.
• Does not include tolerance analysis; treat it as a raw unit conversion.

Worked examples

Deep dive

FAQs

Can I express fractional inches?

Convert decimals to fractions manually (e.g., 0.5 inch = 1/2 inch).

How do I handle cm values?

Convert centimeters to millimeters first (cm × 10), then divide by 25.4 here.

What precision should I use?

For carpentry, hundredths (0.01) of an inch are usually enough. For machining, use more decimals to match your tolerance and tool capabilities.

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