10 mm is about 0.394 inches, or about 25/64 inch (slightly more). It is exactly 1 cm. Divide millimeters by 25.4, because 1 inch is defined as exactly 25.4 mm.
10 mm ≈ 25/64″
Slightly more than 25/64″ (by 0.08 mm) · ≈ 0.394 in
- Inches
- ≈ 0.3937 in
- Nearest 1/16″
- 3/8″ 10 mm is 0.48 mm longer
- Nearest 1/32″
- 13/32″ 10 mm is 0.32 mm shorter
- Nearest 1/64″
- 25/64″ 10 mm is 0.08 mm longer
How big is 10 mm?
10 mm = 10 ÷ 25.4 in ≈ 0.39370 in. On a tape measure that is 25/64 in (0.3906 in, 9.922 mm), and 10 mm is longer than that by about 0.08 mm, less than the thickness of a sheet of paper. In other metric units, 10 mm is exactly 1 cm and exactly 0.01 m.
Compared with other common fractions: 3/8 in is 9.525 mm, so 10 mm is about 0.48 mm more; 13/32 in is 10.319 mm, so 10 mm is about 0.32 mm less.
Things that are about 10 mm
These are nominal sizes. Real parts vary a little with the maker, so check the part when fit matters.
An M10 bolt or screw
The “M10” label means a thread diameter of 10 mm. A standard hex head M10 bolt takes a 16 mm or 17 mm wrench depending on the standard, and an M10 socket head screw takes an 8 mm hex key.
A 10 mm drill bit
A standard metric bit size. The closest fraction bit, 25/64 in, drills a hole about 0.08 mm smaller. A 3/8 in bit drills one about 0.48 mm smaller.
10 mm panel board
Plywood, MDF and similar boards are sold in 10 mm thickness. Compared with inch sizes, 10 mm is a little more than 3/8 in (9.525 mm).
One centimeter on a ruler
The gap between two numbered marks on a metric ruler is exactly 10 mm, about 0.39 of an inch.
A 10 mm bead
10 mm is a common round bead size in jewelry and crafts, about 0.39 of an inch across.
Nearby millimeter sizes
Decimals are rounded to 3 places. In the fraction columns, + means the value is slightly longer than the fraction, − slightly shorter, and = exact.
| Millimeters (mm) | Inches (decimal) | Nearest 1/16″ | Nearest 1/32″ |
|---|---|---|---|
| 5 mm | 0.197 | 3/16″ + | 3/16″ + |
| 6 mm | 0.236 | 1/4″ − | 1/4″ − |
| 7 mm | 0.276 | 1/4″ + | 9/32″ − |
| 8 mm | 0.315 | 5/16″ + | 5/16″ + |
| 9 mm | 0.354 | 3/8″ − | 11/32″ + |
| 10 mm | 0.394 | 3/8″ + | 13/32″ − |
| 11 mm | 0.433 | 7/16″ − | 7/16″ − |
| 12 mm | 0.472 | 1/2″ − | 15/32″ + |
| 13 mm | 0.512 | 1/2″ + | 1/2″ + |
| 14 mm | 0.551 | 9/16″ − | 9/16″ − |
| 15 mm | 0.591 | 9/16″ + | 19/32″ − |
Frequently asked questions
How many inches is 10 mm?
10 mm is about 0.394 inches (0.3937 in), or about 25/64 inch, slightly more.
What is 10 mm as a fraction of an inch?
About 25/64 inch. 10 mm is 0.3937 in and 25/64 in is 0.390625 in, so 10 mm is slightly more.
Is 10 mm the same as 3/8 inch?
No. 3/8 inch is 9.525 mm, so 10 mm is about 0.48 mm larger.
How many cm is 10 mm?
10 mm is exactly 1 cm, because 1 cm is 10 mm.
Can I use a 3/8 inch drill bit for a 10 mm hole?
The hole will be about 0.48 mm smaller than 10 mm, which is too tight for a 10 mm bolt. Use a 10 mm bit, or a 13/32 inch bit (10.319 mm) for a loose fit.
How do I convert mm to inches?
Divide the millimeters by 25.4. For 10 mm, 10 ÷ 25.4 ≈ 0.394 inches.