kilogram per square metre

SI coherent derived unit

Name	Symbol	Quantity	Base units
kilogram per square metre	kg m⁻²	surface density	kg m⁻²
The kilogram per square metre, symbol kg m⁻², is the SI coherent derived unit of surface density. An area of one square metre with a mass of one kilogram has a surface density of one kilogram per square metre.
Definition			h c^-4 Δν_Cs³
$1 \mspace{4mu} \text{kg} \mspace{4mu} \text{m}^{-2} \mspace{6mu} = \dfrac{(299 \mspace{4mu} 792 \mspace{4mu} 458)^4}{(6.626 \mspace{4mu} 070 \mspace{4mu} 15 \times 10^{-34})(9 \mspace{4mu} 192 \mspace{4mu} 631 \mspace{4mu} 770)^3} \mspace{6mu} \dfrac{h \mspace{4mu} {\Delta \nu _{Cs}}^3}{c^4}\\ \\ \\ 1 \mspace{4mu} \text{kg} \mspace{4mu} \text{m}^{-2} \mspace{6mu} \approx 1.569 \mspace{4mu} 304 \mspace{4mu} 393 \mspace{4mu} 397 \mspace{4mu} 563 \mspace{4mu} 377 \times10^{37} \mspace{6mu} h \mspace{4mu} c^{-4} \mspace{4mu} {\Delta \nu _{Cs}}^3$

Paper

The surface density of paper is measured in units of grams per square metre, symbol g/m².

Body mass index

Body mass index (BMI) is defined as body mass divided by the square of body height. BMI is expressed in units of kg/m², although in common use the units are generally omitted.