Square Mm to Square Km Converter (mm² to km²)

How to convert square millimeters to square kilometers

Formulakm² = mm² × 1×10⁻¹²

Multiply the value in square millimeters by 1×10⁻¹². To go the other way, multiply by 1,000,000,000,000 (or divide by 1×10⁻¹²).

A square millimeter is smaller than a square kilometer: it takes 1,000,000,000,000 square millimeters to make one square kilometer.

Worked examples

1 square millimeter1 mm² × 1×10⁻¹² = 1×10⁻¹² km²
5 square millimeters5 mm² × 1×10⁻¹² = 5×10⁻¹² km²
10 square millimeters10 mm² × 1×10⁻¹² = 1×10⁻¹¹ km²
20 square millimeters20 mm² × 1×10⁻¹² = 2×10⁻¹¹ km²
100 square millimeters100 mm² × 1×10⁻¹² = 1×10⁻¹⁰ km²

Square millimeters to square kilometers conversion table

Values are calculated by the conversion engine and rounded to 8 significant figures.

Square millimeters to square kilometers: 0.1–10 mm²
Square millimeters (mm²)	Square kilometers (km²)
0.1 mm²	1×10⁻¹³ km²
0.25 mm²	2.5×10⁻¹³ km²
0.5 mm²	5×10⁻¹³ km²
1 mm²	1×10⁻¹² km²
2 mm²	2×10⁻¹² km²
3 mm²	3×10⁻¹² km²
4 mm²	4×10⁻¹² km²
5 mm²	5×10⁻¹² km²
6 mm²	6×10⁻¹² km²
7 mm²	7×10⁻¹² km²
8 mm²	8×10⁻¹² km²
9 mm²	9×10⁻¹² km²
10 mm²	1×10⁻¹¹ km²

Square millimeters to square kilometers: 12–1,000 mm²
Square millimeters (mm²)	Square kilometers (km²)
12 mm²	1.2×10⁻¹¹ km²
15 mm²	1.5×10⁻¹¹ km²
20 mm²	2×10⁻¹¹ km²
25 mm²	2.5×10⁻¹¹ km²
30 mm²	3×10⁻¹¹ km²
40 mm²	4×10⁻¹¹ km²
50 mm²	5×10⁻¹¹ km²
75 mm²	7.5×10⁻¹¹ km²
100 mm²	1×10⁻¹⁰ km²
250 mm²	2.5×10⁻¹⁰ km²
500 mm²	5×10⁻¹⁰ km²
1,000 mm²	1×10⁻⁹ km²

About the units

Square millimeter (mm²)

Used for wire cross-sections in metric countries (e.g. 2.5 mm² cable). One square millimeter equals 0.000001 square meters (m²).

Square kilometer (km²)

One million square metres or 100 hectares; used for city, lake and country areas. One square kilometer equals 1,000,000 square meters (m²).

Frequently asked questions

How many square kilometers are in one square millimeter?

There are 1×10⁻¹² square kilometers in one square millimeter, and this value is exact by definition.

How do I convert square millimeters to square kilometers?

Multiply the number of square millimeters by 1×10⁻¹². For example, 10 mm² × 1×10⁻¹² = 1×10⁻¹¹ km².

How many square millimeters are in one square kilometer?

One square kilometer equals 1,000,000,000,000 square millimeters. That is the reverse factor, 1 ÷ 1×10⁻¹².

What is 10 square millimeters in square kilometers?

10 mm² = 1×10⁻¹¹ km².

Is this mm² to km² converter accurate?

Yes. Both units are defined exactly in terms of SI units, so the conversion factor is exact; results are shown to 12 significant figures by default and you can change precision in the converter. Calculations run in your browser using the same tested engine that generated this page.

Square Mm to Square Km Converter