20 mm is about 0.787 inches, or about 25/32 inch (slightly more). It is exactly 2 cm. Divide millimeters by 25.4, because 1 inch is defined as exactly 25.4 mm.
20 mm ≈ 25/32″
Slightly more than 25/32″ (by 0.16 mm) · ≈ 0.787 in
- Inches
- ≈ 0.7874 in
- Nearest 1/16″
- 13/16″ 20 mm is 0.64 mm shorter
- Nearest 1/32″
- 25/32″ 20 mm is 0.16 mm longer
- Nearest 1/64″
- 25/32″ 20 mm is 0.16 mm longer
How big is 20 mm?
20 mm = 20 ÷ 25.4 in ≈ 0.78740 in. On a tape measure that is 25/32 in (0.7812 in, 19.844 mm), and 20 mm is longer than that by about 0.16 mm. In other metric units, 20 mm is exactly 2 cm and exactly 0.02 m.
Compared with common fractions: 25/32 in is 19.844 mm, so 20 mm is about 0.16 mm more; 3/4 in is 19.05 mm, so 20 mm is 0.95 mm more.
Things that are about 20 mm
These are nominal sizes. Real parts vary a little with the maker, so check the part when fit matters.
An M20 bolt or screw
The “M20” label means a thread diameter of 20 mm, about 0.79 of an inch.
A US penny
A US one-cent coin is 19.05 mm across (exactly 0.75 in), so it is 0.95 mm narrower than 20 mm.
A US nickel
A US five-cent coin is 21.21 mm across, so it is 1.21 mm wider than 20 mm.
Three quarters of an inch
3/4 in is exactly 19.05 mm, so 20 mm is 0.95 mm longer. 20 mm and 3/4 in are close but not the same size.
20 mm electrical conduit
Conduit sold as 20 mm has a nominal outer diameter of 20 mm, about 0.79 in.
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″ |
|---|---|---|---|
| 15 mm | 0.591 | 9/16″ + | 19/32″ − |
| 16 mm | 0.63 | 5/8″ + | 5/8″ + |
| 17 mm | 0.669 | 11/16″ − | 21/32″ + |
| 18 mm | 0.709 | 11/16″ + | 23/32″ − |
| 19 mm | 0.748 | 3/4″ − | 3/4″ − |
| 20 mm | 0.787 | 13/16″ − | 25/32″ + |
| 21 mm | 0.827 | 13/16″ + | 13/16″ + |
| 22 mm | 0.866 | 7/8″ − | 7/8″ − |
| 23 mm | 0.906 | 7/8″ + | 29/32″ − |
| 24 mm | 0.945 | 15/16″ + | 15/16″ + |
| 25 mm | 0.984 | 1″ − | 31/32″ + |
Frequently asked questions
How many inches is 20 mm?
20 mm is about 0.787 inches (0.7874 in), or about 25/32 inch, slightly more.
What is 20 mm as a fraction of an inch?
About 25/32 inch. 20 mm is 0.7874 in and 25/32 in is 0.78125 in, so 20 mm is slightly more.
Is 20 mm the same as 3/4 inch?
No. 3/4 inch is 19.05 mm, so 20 mm is 0.95 mm bigger. For a close fit you may need a 25/32 inch size (19.844 mm).
How many mm is a US penny?
A US penny is 19.05 mm across, which is exactly 0.75 inch.
How many cm is 20 mm?
20 mm is exactly 2 cm, because 1 cm is 10 mm.
How do I convert mm to inches?
Divide the millimeters by 25.4. For 20 mm, 20 ÷ 25.4 ≈ 0.787 inches.