4 mm to Inches
Convert 4 millimeters to inches — instant, accurate, and easy
The Answer
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📄 Free printable mm to inches chart (PDF) — every mm from 1 to 300.
How to Convert 4 mm to Inches
To convert 4 millimeters to inches, divide the millimeter value by 25.4. This is because one inch equals exactly 25.4 millimeters — a standard defined by international agreement.
The Calculation
Applying the formula to 4 mm:
Result Summary for 4 mm
- Decimal inches: 0.1575″
- Fractional inches: 5/32″ (nearest 1/64)
- Feet and inches: 0 ft 0.16 in
4 mm Compared With 5/32 Inch
4 mm is approximately 0.1575 inches. The nearest 1/16-inch mark is 3/16 inch (4.7625 mm), 0.7625 mm above 4 mm.
A 5/32-inch drill bit is 3.9688 mm, so it is 0.0313 mm smaller than 4 mm. The two are close enough that a 5/32-inch bit is often used where a 4 mm hole is called for.
An M4 screw has a nominal major diameter of 4 mm. The closest inch machine screw is #8, which is 0.164 inch (4.17 mm).
Reference Table — Values Near 4 mm
| Millimeters | Decimal Inches | Fractional Inches |
|---|---|---|
| 1 mm | 0.0394″ | 3/64″ |
| 2 mm | 0.0787″ | 5/64″ |
| 3 mm | 0.1181″ | 1/8″ |
| 4 mm | 0.1575″ | 5/32″ |
| 5 mm | 0.1969″ | 13/64″ |
| 6 mm | 0.2362″ | 15/64″ |
| 7 mm | 0.2756″ | 9/32″ |
4 mm in Other Units
Millimeters convert cleanly into every other length unit. Here is 4 mm expressed seven different ways — useful when a drawing, spec sheet or supplier quotes a unit other than inches.
| Unit | 4 mm equals |
|---|---|
| Centimeters (cm) | 0.4 cm |
| Meters (m) | 0.004 m |
| Inches (in) | 0.1575 in |
| Feet (ft) | 0.0131 ft |
| Yards (yd) | 0.00437 yd |
| Thousandths of an inch (mil) | 157.5 mil |
| Typographic points (1/72 in) | 11.34 pt |
How Accurate Is Each Fraction of 4 mm?
4 mm equals 0.1575″ (rounded to four decimal places). Any fraction is a further rounding of the full-precision value, so each one carries a small error. This table shows the closest fraction at each common denominator and how far it actually sits from 4 mm.
| Rounded to | Fraction | Decimal | Fraction vs. original |
|---|---|---|---|
| Nearest 1/2″ | 0″ | 0.0000″ | −4.000 mm (below original) |
| Nearest 1/4″ | 1/4″ | 0.2500″ | +2.350 mm (above original) |
| Nearest 1/8″ | 1/8″ | 0.1250″ | −0.825 mm (below original) |
| Nearest 1/16″ | 3/16″ | 0.1875″ | +0.763 mm (above original) |
| Nearest 1/32″ | 5/32″ | 0.1563″ | −0.031 mm (below original) |
| Nearest 1/64″ | 5/32″ | 0.1563″ | −0.031 mm (below original) |
For woodworking, DIY and general workshop use, 5/32″ is the practical choice — it lands within 0.4 mm of 4 mm. For machining, toolmaking or CAD, use the decimal value 0.1575″ rather than any fraction.
FAQ About 4 mm to Inches
How many inches is 4 mm?
4 millimeters equals 0.1575 inches (rounded to 4 decimal places), or approximately 5/32″ (nearest 1/64 inch).
How accurate is the 4 mm to inches conversion?
The conversion of 4 mm to 0.1575 inches uses the exact definition 1 inch = 25.4 millimeters; the four-decimal result is rounded, so it is approximate.
Can I convert 4 mm to feet?
Yes. 4 millimeters equals approximately 0 ft 0.16 in.
📏 Need to measure 4mm accurately?
Digital calipers typically display readings to 0.01 mm resolution, enough to check 4 mm (≈ 0.1575″). See current options:
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