| metric inch | 1 in (metric) | 2 in (metric) | 3 in (metric) | 4 in (metric) | 5 in (metric) | 6 in (metric) | 7 in (metric) | 8 in (metric) | 9 in (metric) | 10 in (metric) | 11 in (metric) | 12 in (metric) | 13 in (metric) | 14 in (metric) | 15 in (metric) | 16 in (metric) | 17 in (metric) | 18 in (metric) | 19 in (metric) | 20 in (metric) | 21 in (metric) | 22 in (metric) | 23 in (metric) | 24 in (metric) | 25 in (metric) | 26 in (metric) | 27 in (metric) | 28 in (metric) | 29 in (metric) | 30 in (metric) | 31 in (metric) | 32 in (metric) | 33 in (metric) | 34 in (metric) | 35 in (metric) | 36 in (metric) | 37 in (metric) | 38 in (metric) | 39 in (metric) | 40 in (metric) | 41 in (metric) | 42 in (metric) | 43 in (metric) | 44 in (metric) | 45 in (metric) | 46 in (metric) | 47 in (metric) | 48 in (metric) | 49 in (metric) | 50 in (metric) | 51 in (metric) | 52 in (metric) | 53 in (metric) | 54 in (metric) | 55 in (metric) | 56 in (metric) | 57 in (metric) | 58 in (metric) | 59 in (metric) | 60 in (metric) | 61 in (metric) | 62 in (metric) | 63 in (metric) | 64 in (metric) | 65 in (metric) | 66 in (metric) | 67 in (metric) | 68 in (metric) | 69 in (metric) | 70 in (metric) | 71 in (metric) | 72 in (metric) | 73 in (metric) | 74 in (metric) | 75 in (metric) | 76 in (metric) | 77 in (metric) | 78 in (metric) | 79 in (metric) | 80 in (metric) | 81 in (metric) | 82 in (metric) | 83 in (metric) | 84 in (metric) | 85 in (metric) | 86 in (metric) | 87 in (metric) | 88 in (metric) | 89 in (metric) | 90 in (metric) | 91 in (metric) | 92 in (metric) | 93 in (metric) | 94 in (metric) | 95 in (metric) | 96 in (metric) | 97 in (metric) | 98 in (metric) | 99 in (metric) | 100 in (metric) |
| french; charriere | 1.2 F | 2.4 F | 3.6 F | 4.8 F | 6 F | 7.2 F | 8.4 F | 9.6 F | 10.8 F | 12 F | 13.2 F | 14.4 F | 15.6 F | 16.8 F | 18 F | 19.2 F | 20.4 F | 21.6 F | 22.8 F | 24 F | 25.2 F | 26.4 F | 27.6 F | 28.8 F | 30 F | 31.2 F | 32.4 F | 33.6 F | 34.8 F | 36 F | 37.2 F | 38.4 F | 39.6 F | 40.8 F | 42 F | 43.2 F | 44.4 F | 45.6 F | 46.8 F | 48 F | 49.2 F | 50.4 F | 51.6 F | 52.8 F | 54 F | 55.2 F | 56.4 F | 57.6 F | 58.8 F | 60 F | 61.2 F | 62.4 F | 63.6 F | 64.8 F | 66 F | 67.2 F | 68.4 F | 69.6 F | 70.8 F | 72 F | 73.2 F | 74.4 F | 75.6 F | 76.8 F | 78 F | 79.2 F | 80.4 F | 81.6 F | 82.8 F | 84 F | 85.2 F | 86.4 F | 87.6 F | 88.8 F | 90 F | 91.2 F | 92.4 F | 93.6 F | 94.8 F | 96 F | 97.2 F | 98.4 F | 99.6 F | 100.8 F | 102 F | 103.2 F | 104.4 F | 105.6 F | 106.8 F | 108 F | 109.2 F | 110.4 F | 111.6 F | 112.8 F | 114 F | 115.2 F | 116.4 F | 117.6 F | 118.8 F | 120 F |
A metric inch is a nickname for a preferred 1⁄4 subdivision of an ISO 2848 basic module, or 1⁄12 of a metric foot measuring 25 millimetres (0.984 in). A metric inch is 0.4 millimetres (0.016 in) shorter than an inch.
The term was similarly used to refer to the historical Soviet Bloc practice of spacing integrated circuit pins at 1⁄10 of a 25 mm "metric inch" length, instead of the western practice of 1⁄10 of an imperial inch.
| Name of unit | Symbol | Definition | Relation to SI units | Unit System |
|---|---|---|---|---|
| metric inch | in (metric) | = 0.016 in | = 0.0004 m | Metric system SI |
| metric inches | french; charriere | metric inches | french; charriere |
|---|---|---|---|
| 1 | = 1.2 | 4 | = 4.8 |
| 1.5 | = 1.8 | 4.5 | = 5.4 |
| 2 | = 2.4 | 5 | = 6 |
| 2.5 | = 3 | 5.5 | = 6.6 |
| 3 | = 3.6 | 6 | = 7.2 |
The French scale or French gauge system is commonly used to measure the size of a catheter. It is most often abbreviated as Fr, but can often be seen abbreviated as Fg, Ga, FR or F. It may also be abbreviated as CH or Ch (for Charrière, its inventor).
| Name of unit | Symbol | Definition | Relation to SI units | Unit System |
|---|---|---|---|---|
| french; charriere | F | ≡ 1⁄3 mm | = 0.3×10−3 m | Other (Length) |
| french; charriere | metric inches | french; charriere | metric inches |
|---|---|---|---|
| 1 | = 0.83333333333333 | 4 | = 3.3333333333333 |
| 1.5 | = 1.25 | 4.5 | = 3.75 |
| 2 | = 1.6666666666667 | 5 | = 4.1666666666667 |
| 2.5 | = 2.0833333333333 | 5.5 | = 4.5833333333333 |
| 3 | = 2.5 | 6 | = 5 |
| metric inches | french; charriere |
|---|---|
| 1 | = 1.2 |
| 0.8333333 | = 1 |
| Symbol | Definition |
|---|---|
| ≡ | exactly equal |
| ≈ | approximately equal to |
| = | equal to |
| digits | indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369 …) |