MM to Inches Converter — Engineering, Screen Sizes & Jewelry Table
Convert millimeters to inches with a precision reference table. Covers engineering tolerances, screen dimensions, ring sizes, and drill bits. Includes reverse inches-to-mm.
One millimeter equals 0.0393701 inches, or about 1/25th of an inch. The precise conversion: 1 inch = 25.4 mm exactly. So going mm → inches means dividing by 25.4.
CalcHub's mm to inches converter handles any precision you need. The table below covers the ranges most useful in engineering, electronics, and jewelry.The Formula
inches = millimeters ÷ 25.4Reverse:
millimeters = inches × 25.4MM to Inches Reference Table (1–50 mm)
| mm | inches | mm | inches |
|---|---|---|---|
| 1 | 0.0394 | 14 | 0.5512 |
| 2 | 0.0787 | 15 | 0.5906 |
| 3 | 0.1181 | 16 | 0.6299 |
| 4 | 0.1575 | 17 | 0.6693 |
| 5 | 0.1969 | 18 | 0.7087 |
| 6 | 0.2362 | 19 | 0.7480 |
| 7 | 0.2756 | 20 | 0.7874 |
| 8 | 0.3150 | 25 | 0.9843 |
| 9 | 0.3543 | 30 | 1.1811 |
| 10 | 0.3937 | 35 | 1.3780 |
| 11 | 0.4331 | 40 | 1.5748 |
| 12 | 0.4724 | 45 | 1.7717 |
| 13 | 0.5118 | 50 | 1.9685 |
Screen & Display Sizes
Monitor and phone bezels, screen borders, and camera sensor sizes are specified in mm by manufacturers but often need conversion for US consumers.
| Device | mm | Inches |
|---|---|---|
| Phone width (typical) | 70–77 mm | 2.76–3.03" |
| Laptop bezel | 5–15 mm | 0.20–0.59" |
| Camera sensor (Micro 4/3) | 17.3 × 13 mm | 0.68" × 0.51" |
| Full-frame sensor | 36 × 24 mm | 1.42" × 0.94" |
| Credit card thickness | 0.76 mm | 0.030" |
Jewelry & Ring Sizes
Ring sizes in India and internationally are measured in mm (inner circumference or diameter). US ring sizes use a different numeric system.
| Ring Diameter (mm) | US Ring Size |
|---|---|
| 14.9 mm | Size 4 |
| 15.7 mm | Size 5 |
| 16.5 mm | Size 6 |
| 17.3 mm | Size 7 |
| 18.2 mm | Size 8 |
| 19.0 mm | Size 9 |
| 19.8 mm | Size 10 |
Drill Bits & Fasteners
US drill bits use fractional inches; metric drill bits use mm. Common overlap sizes:
| mm | Closest Imperial Fraction | Decimal Inches |
|---|---|---|
| 3 mm | 1/8" | 0.125" |
| 4 mm | 5/32" | 0.156" |
| 5 mm | 13/64" | 0.203" |
| 6 mm | 15/64" | 0.234" |
| 8 mm | 5/16" | 0.313" |
| 10 mm | 25/64" | 0.391" |
| 12 mm | 15/32" | 0.469" |
How many mm is 1/4 inch?
1/4 × 25.4 = 6.35 mm.
What is 10mm in inches?
10 ÷ 25.4 = 0.3937 inches, approximately 25/64" or just under 13/32".
Is 25mm the same as 1 inch?
Close — 25 mm = 0.984 inches. 1 inch = 25.4 mm. They're nearly identical but not the same.