Calculator
Use single input or batch mode for many values.
Exports use your most recent calculation.
Example Data Table
| Millimeters (mm) | Inches (decimal) | Centimeters | Meters |
|---|---|---|---|
| 1 | 0.039370 | 0.100 | 0.0010 |
| 10 | 0.393701 | 1.000 | 0.0100 |
| 12.7 | 0.500000 | 1.270 | 0.0127 |
| 25.4 | 1.000000 | 2.540 | 0.0254 |
| 100 | 3.937008 | 10.000 | 0.1000 |
Example: 25.4 mm equals exactly 1.000000 in.
Formula Used
This converter turns millimeters into a decimal value using fixed unit relationships. The core conversion is dividing by the millimeters-per-unit constant.
- inches = mm ÷ 25.4
- centimeters = mm ÷ 10
- meters = mm ÷ 1000
- feet = mm ÷ 304.8
Rounding is applied after conversion using your chosen decimal places and mode.
How to Use This Calculator
- Enter a millimeter value, or enable batch mode.
- Select the target unit and decimal places.
- Pick a rounding method for your tolerance needs.
- Press Convert to see results above the form.
- Use the download buttons to export CSV or PDF.
FAQs
1) What does “decimal” mean here?
It means the result is shown as a decimal number, not a fraction. For example, 12.7 mm becomes 0.5000 inches when using four decimal places.
2) Why is 25.4 used for inches?
Because one inch is defined as exactly 25.4 millimeters. Dividing millimeters by 25.4 converts the length into decimal inches.
3) Which rounding option should I choose?
Use Nearest for general work. Use Up to avoid undersizing a measurement, and Down to avoid oversizing. Pick what matches your tolerance requirement.
4) Can I convert many values at once?
Yes. Turn on batch mode, then paste a list of millimeter values separated by spaces, commas, or new lines. The results will appear as a numbered table.
5) What precision should I use for machining?
Common choices are 3 to 4 decimals for inches, depending on your drawing and tools. If you need tighter control, increase decimals and use Up or Down rounding.
6) Are negative millimeter values allowed?
Yes. Negative values can represent direction, offsets, or relative positions. The converter keeps the sign and converts the magnitude using the same unit constants.
7) Why do exports require a recent calculation?
The CSV and PDF downloads use your latest computed result set for accuracy and convenience. If you change settings, press Convert again before exporting.
8) How do I verify the conversion quickly?
Use a known reference: 25.4 mm equals 1 inch exactly, and 10 mm equals 1 centimeter. If your outputs match these, your settings are correct.