Square Millimeter (mm²)
A square one millimeter on a side. Used for the cross-section of wires and small parts.
1 square millimeter = 0.000001 square meters (exactly).
About the square millimeter
Gauss gets the credit for putting the millimeter at the base of a scientific measuring system. His 1832 proposal for absolute units used the millimeter, milligram and second, although the centimeter-based CGS system later won out among scientists. The square millimeter is a one-thousandth-by-one-thousandth square of a meter, so it takes a million of them to make a square meter, and it has no famous inventor of its own.
Electricians know it best. Wire and cable sizes are given as the cross-sectional area of the copper conductor, and the standard sizes listed for UK domestic wiring are 1, 1.5, 2.5, 4, 6 and 10 mm². Twin and earth cable of 2.5 mm² typically serves sockets on a 16 A radial or 32 A ring circuit, 1 mm² serves lighting on a 6 A breaker, and 4 mm² feeds a cooker or shower. Conductor size depends on current capacity and allowed voltage drop, not on voltage alone. One square inch is exactly 645.16 mm², so small parts in either system compare easily.
Sources: Wikipedia: Electrical wiring in the United Kingdom; Wikipedia: Centimetre-gram-second system of units; Wikipedia: Square metre
Square Millimeter conversion chart
1 square millimeter expressed in every other area unit:
| Unit | 1 square millimeter |
|---|---|
| Square Meters | 0.000001 |
| Square Kilometers | 1×10⁻¹² |
| Hectares | 1×10⁻¹⁰ |
| Square Inches | 0.0015500031 |
| Square Feet | 0.00001076391042 |
| Square Yards | 0.000001195990046 |
| Acres | 2.471053815×10⁻¹⁰ |
| Square Miles | 3.861021585×10⁻¹³ |
| Square Centimeters | 0.01 |
| Tsubo | 3.025×10⁻⁷ |
| Pyeong | 3.025×10⁻⁷ |
| Rai (Thai) | 6.25×10⁻¹⁰ |
| Barns | 1×10²² |
| Ares | 1×10⁻⁸ |
| Square Rods | 3.953686103×10⁻⁸ |
| Square Chains | 2.471053815×10⁻⁹ |
| Roods | 9.884215259×10⁻¹⁰ |
| Oxgangs | 1.64736921×10⁻¹¹ |
| Virgates | 8.236846049×10⁻¹² |
| Hides | 2.059211512×10⁻¹² |
| US Survey Acres | 2.47104393×10⁻¹⁰ |
| Sections | 3.861006141×10⁻¹³ |
| Townships | 1.072501706×10⁻¹⁴ |
| Iugera | 3.963000162×10⁻¹⁰ |
| Jō (tatami Mat) | 6.05×10⁻⁷ |
| Se | 1.008333333×10⁻⁸ |
| Tan | 1.008333333×10⁻⁹ |
| Chō (area) | 1.008333333×10⁻¹⁰ |
| Mu (Chinese) | 1.5×10⁻⁹ |
| Qing (Chinese) | 1.5×10⁻¹¹ |
| Ngan (Thai) | 2.5×10⁻⁹ |
| Square Wa (Thai) | 2.5×10⁻⁷ |
| Guntha | 9.884215259×10⁻⁹ |
| Cents (India) | 2.471053815×10⁻⁸ |
| Marlas | 3.953686103×10⁻⁸ |
| Kanals | 1.976843052×10⁻⁹ |
| Dunams | 1×10⁻⁹ |
| Feddans | 2.380952381×10⁻¹⁰ |
| Arpents | 2.924925926×10⁻¹⁰ |
More Metric (SI) units
- square meter (area)
- square kilometer (area)
- hectare (area)
- square centimeter (area)
- are (area)
- meter (length)
- kilometer (length)
- centimeter (length)
- millimeter (length)
- micrometer (length)
- nanometer (length)
- picometer (length)
- decimeter (length)
- hectometer (length)
- decameter (length)
- kilogram (weight & mass)
Browse all area units.