Metric Conversion Table
In industries such as electrical engineering, construction, and other technical fields, converting between metric and imperial units is a routine task. These conversions can be crucial for maintaining accuracy of designs, calculations, and projects. This guide below offers a detailed table for converting square millimeters to square inches in circular mils, as well as other key conversions for length, area, volume, and mass.
A common requirement in electrical work is converting between square millimeters (mm2), square inches (in2), and circular mils (CM). Circular mils are a unit of area specifically used for measuring the cross-sectional area of electrical conductors. One circular mil is the area of a circle with a diameter of one mil (one-thousandth of an inch).
Square Millimeters to Square Inches / Circular Mils
| Square Millimeters | Square Inches | Circular Mils | Square Millimeters | Square Inches | Circular Mils | Square Millimeters | Square Inches | Circular Mils |
|---|---|---|---|---|---|---|---|---|
| 1,000 | 1.550 | 1,974,000 | - | - | - | - | - | - |
| 975 | 1.511 | 1,924,700 | 95 | 0.1472 | 187,530 | 9.5 | 0.01472 | 18,753 |
| 950 | 1.472 | 1,875,300 | 90 | 0.1395 | 177,660 | 9.0 | 0.01395 | 17,766 |
| 925 | 1.434 | 1,826,000 | 85 | 0.1317 | 167,790 | 8.5 | 0.01317 | 16,779 |
| 900 | 1.395 | 1,776,600 | 80 | 0.1240 | 157,920 | 8.0 | 0.01240 | 15,792 |
| 875 | 1.356 | 1,727,300 | 75 | 0.1163 | 148,050 | 7.5 | 0.01163 | 14,805 |
| 850 | 1.317 | 1,677,900 | 70 | 0.1085 | 138,180 | 7.0 | 0.01085 | 13,818 |
| 825 | 1.240 | 1,579,200 | 60 | 0.0930 | 118,440 | 6.0 | 0.00930 | 11,844 |
| 775 | 1.201 | 1,529,900 | 55 | 0.0853 | 108,570 | 5.5 | 0.00853 | 10,857 |
| 750 | 1.163 | 1,480,500 | 50 | 0.0775 | 98,700 | 5.0 | 0.00775 | 9,870 |
| 725 | 1.124 | 1,431,200 | 45 | 0.0698 | 88,830 | 4.75 | 0.00736 | 9,377 |
| 700 | 1.085 | 1,381,800 | 40 | 0.0620 | 78,960 | 4.50 | 0.00698 | 8,883 |
| 675 | 1.046 | 1,332,500 | 35 | 0.0542 | 69,090 | 4.25 | 0.00659 | 8,390 |
| 650 | 1.008 | 1,283,100 | 30 | 0.0465 | 59,220 | 4.00 | 0.00620 | 7,896 |
| 625 | 0.969 | 1,233,800 | 25 | 0.0388 | 49,350 | 3.75 | 0.00581 | 7,403 |
| 600 | 0.930 | 1,184,400 | 20 | 0.0310 | 39,480 | 3.50 | 0.00542 | 6,909 |
| 575 | 0.891 | 1,135,100 | 19.5 | 0.0302 | 38,490 | 3.25 | 0.00504 | 6,416 |
| 550 | 0.891 | 1,085,700 | 19.0 | 0.0294 | 37,510 | 3.00 | 0.00465 | 5,922 |
| 525 | 0.814 | 1,036,400 | 18.5 | 0.0287 | 35,530 | 2.75 | 0.00426 | 4,935 |
| 500 | 0.775 | 987,000 | 18.0 | 0.0279 | 35,530 | 2.50 | 0.00388 | 4,935 |
| 475 | 0.736 | 937,700 | 17.5 | 0.0271 | 34,550 | 2.25 | 0.00349 | 4,442 |
| 450 | 0.698 | 888,300 | 17.0 | 0.0264 | 33,560 | 2.00 | 0.00310 | 3,948 |
| 425 | 0.659 | 839,000 | 16.5 | 0.0256 | 32,560 | 1.75 | 0.00271 | 3,455 |
| 400 | 0.620 | 789,600 | 16.0 | 0.0248 | 31,580 | 1.50 | 0.00233 | 2,961 |
| 375 | 0.581 | 740,300 | 15.5 | 0.0240 | 30,600 | 1.25 | 0.00194 | 2,468 |
| 350 | 0.542 | 690,900 | 15.0 | 0.0233 | 29,610 | 1.00 | 0.00155 | 1,974 |
| 325 | 0.504 | 641,600 | 14.5 | 0.0225 | 28,620 | 0.90 | 0.00140 | 1,777 |
| 300 | 0.465 | 592,200 | 14.0 | 0.0217 | 27,640 | 0.80 | 0.00124 | 1,579 |
| 275 | 0.426 | 542,900 | 13.5 | 0.0209 | 26,650 | 0.75 | 0.00116 | 1,481 |
| 250 | 0.388 | 493,500 | 13.0 | 0.0201 | 26,650 | 0.70 | 0.00109 | 1,481 |
| 225 | 0.349 | 444,200 | 12.5 | 0.0194 | 24,680 | 0.60 | 0.000930 | 1,184 |
| 200 | 0.310 | 394,800 | 12.0 | 0.0186 | 23,690 | 0.50 | 0.000775 | 987 |
| 175 | 0.291 | 345,500 | 11.5 | 0.0178 | 22,700 | - | - | - |
| 150 | 0.233 | 296,100 | 11.0 | 0.0171 | 21,700 | - | - | - |
| 125 | 0.1938 | 246,800 | 10.5 | 0.0163 | 20,730 | - | - | - |
| 100 | 0.1550 | 197,400 | 10.0 | 0.0155 | 19,740 | - | - | - |
*Based on 1000 sq. mm = 1,974,000 circular mils.
Specialized Electrical Conversions: Resistance and Wire Sizing
For electrical professionals, understanding resistance and wire sizing conversions is essential:
- Resistance Conversion: To convert Ohms per kilometer to Ohms per kilofeet, multiply by 0.3048.
- Circular Mil to Square Mil Conversion: Multiply circular mils by 0.7854 to find the equivalent square mils.
- Calculating Circular Mil Area (CMA): The CMA of a conductor is calculated using the formula:
CMA = (average strand size in mils)² × 1,000,000 × total number of strands
| Length | Area | Volume | Mass |
|---|---|---|---|
| Inch x 25.40 = Millimeters | Sq. Inch x 6.452 = Sq. Centimeter | Cu. Inch x 16.39 = Cu. Centimeter | Ounce x 28.35 = Gram |
| Millimeters x 0.03937 = Inches | Sq. Centimeter x 0.1550 = Sq. Inch | Cu. Centimeter x 0.06102 = Cu. Inch | Gram x 0.03527 = Ounce |
| Feet x 0.3048 = Meters | Sq. Foot x 0.0929 = Sq. Meter | Cu. Foot x 0.02832 = Cu. Meter | Pound x 0.4536 = Kilogram |
| Meters x 3.281 = Kilometers | Sq. Meter x 10.76 = Sq. Foot | Cu. Meter x 35.31 = Cu. Foot | Kilogram x 2.205 = Pound |
| Miles x 1.609 = Kilometers | Sq. Mile x 2.590 = Sq. Kilometer | - | Kilogram/km x 0.6214 = Pounds/kft |
| Kilometers x 0.6214 = Miles | Sq. Kilometer x 0.3861 = Sq. Mile | - | Pounds/kft x 1.4881 = Kilogram/km |
| OHMS/km x 0.3048 = OHMS/kft | Circular Mil x 0.7854 = Sq. Mil | - | - |
Circular Mil Area (CMA) = (average strand size in Mils)2 x 1,000,000 x total number of strands