Convert Square millimetres to Square kilometres
1 square millimetre is 1.00e-12 km². One square millimetre is exactly 1e-12 square kilometres.
One square millimetre is 1.0000 × 10^-12 square kilometres. To convert square millimetres to square kilometres, multiply by 1.0000 × 10^-12; to go the other way, divide by 1.0000 × 10^-12 or multiply by 1000000000000. The relation is exact but the figure is not: it is a rounding of a number that does not terminate, and it follows from NIST Office of Weights and Measures. A millionth of a square metre, because the millimetre is a thousandth of a metre and area squares the factor.
Factor checked against the defining standard · How we check
- Square millimetres × 1.0000 × 10^-12
1 * 1e-120 km²
1 square millimetre in every area unit
| Unit | Value | Exact factor |
|---|---|---|
| square inches | 0.0015500031 sq in | × 0.00155000310001 |
| square feet | 0.00001076391042 sq ft | × 0.0000107639104167 |
| square yards | 0.000001195990046 sq yd | × 0.0000011959900463 |
| acres | 0.0000000002471053815 ac | × 0.000000000247105381467 |
| square meters | 0.000001 m² | × 0.000001 |
| square millimetres (as entered) | 1 mm² | — |
| square centimetres | 0.01 cm² | × 0.01 |
| square kilometres | 0.000000000001 km² | × 0.000000000001 |
| square miles | 0 mi² | × 0.000000000000386102158542 |
| hectares | 0.0000000001 ha | × 0.0000000001 |
Factors are entered by hand from NIST Office of Weights and Measures rather than derived from a units library, so the ones that terminate are exact rather than rounded.
The same converter answers this pair however it is written: sqmm to sqkm is how the symbols are typed on a keyboard with no superscript on it.
How do you convert square millimetres to square kilometres? The converter and the working
- 1.Take the measurement in square millimetres.
- 2.Multiply by 1.0000 × 10^-12 — that is how many square kilometres fit in one square millimetre.
- 3.To go back the other way, divide by 1.0000 × 10^-12, or multiply by 1000000000000.
Worked example: 25 square millimetres to square kilometres
- Formula
- mm² × 1.0000 × 10^-12 = km²
- Arithmetic
- 25 × 1.0000 × 10^-12 = 2.50e-11 km²
- Answer
- 25 mm² = 2.50e-11 km²
The factor is rounded for display; the figure above is computed from the full value.
Square millimetres to square kilometres conversion table
| Square millimetres | Square kilometres |
|---|---|
| 1 mm² | 1.00e-12 km² |
| 2 mm² | 2.00e-12 km² |
| 3 mm² | 3.00e-12 km² |
| 4 mm² | 4.00e-12 km² |
| 5 mm² | 5.00e-12 km² |
| 6 mm² | 6.00e-12 km² |
| 7 mm² | 7.00e-12 km² |
| 8 mm² | 8.00e-12 km² |
| 9 mm² | 9.00e-12 km² |
| 10 mm² | 1.00e-11 km² |
| 12 mm² | 1.20e-11 km² |
| 15 mm² | 1.50e-11 km² |
| 20 mm² | 2.00e-11 km² |
| 25 mm² | 2.50e-11 km² |
| 50 mm² | 5.00e-11 km² |
| 100 mm² | 1.00e-10 km² |
| 200 mm² | 2.00e-10 km² |
| 300 mm² | 3.00e-10 km² |
| 500 mm² | 5.00e-10 km² |
| 1000 mm² | 1.00e-9 km² |
| 2000 mm² | 2.00e-9 km² |
| 5000 mm² | 5.00e-9 km² |
| 10000 mm² | 1.00e-8 km² |
What is a square millimetre?
A millionth of a square metre, because the millimetre is a thousandth of a metre and area squares the factor. The working unit of engineering drawings and of cable cross-sections.
What is a square kilometre?
A million square metres, or 100 hectares. The unit land area and population density are published in everywhere except the US.
How many square kilometres are in a square millimetre?
One square millimetre is 1.0000 × 10^-12 square kilometres. Going the other way, one square kilometre is 1000000000000 square millimetres. Both figures come from the same defined relation rather than from a measurement, which is why they are the same today as they were in 1959.
Every area unit here
The whole group — 10 units with their symbols and the size of each one in square meters — is on the conversion index, along with every pair it makes. The table above already gives each of them relative to a square millimetre.
Cite this page
- APA
- Rule Calculator. (2026). Convert Square millimetres to square kilometres. Rule Calculator. https://rulecalculators.com/convert/square-millimeter-to-square-kilometer
- MLA
- "Convert Square millimetres to square kilometres." Rule Calculator, August 16, 2026, https://rulecalculators.com/convert/square-millimeter-to-square-kilometer.
- Chicago
- Rule Calculator. "Convert Square millimetres to square kilometres." Rule Calculator. Last reviewed August 16, 2026. https://rulecalculators.com/convert/square-millimeter-to-square-kilometer.
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Questions people actually ask
- How many square kilometres are in a square millimetre?
- 1.0000 × 10^-12. A million square metres, or 100 hectares. The unit land area and population density are published in everywhere except the US.
- How do I convert square kilometres back to square millimetres?
- Divide by 1.0000 × 10^-12, or multiply by 1000000000000 — they are the same operation.
Other area conversions
Square kilometres to square millimetres — the same conversion the other way.