What is the density of gypsum board (drywall)?

700 kg/m³ (640–800), or 0.70 g/cm³.

Does gypsum board (drywall) float?

Yes. At 700 kg/m³ it is less dense than water's 1,000.

Gypsum board (drywall)

Density of gypsum board (drywall)

700 kg/m³ (640–800)

0.70 g/cm³ · 43.7 lb/ft³

A 12.5 mm sheet weighs about 9 kg/m², so a standard 2400 × 1200 board is roughly 25 kg — right at the edge of a one-person lift, which is why 9.5 mm exists. Its fire rating comes entirely from the chemically bound water in the gypsum core boiling off and holding the far face near 100 °C, which is why fire-rated partitions are specified as layers of board rather than as any special material. It has almost no structural strength, so anything heavy hung on it needs a fixing that reaches the stud or a proper cavity anchor.

Properties

Density: 700 kg/m³ (640–800) — 0.70 g/cm³
Tensile strength: 1–3 MPa
Thermal conductivity: 0.17 W/(m·K)
Floats in water: Yes
Magnetic: No

What it is used for

Internal wall and ceiling linings
Fire-rated partitions and shaft walls
Suspended ceiling tiles
Acoustic separating walls

How it compares

Water is 1,000 kg/m³. Anything with a shorter bar than water floats in it.

air 1.2 kg/m³

expanded polystyrene foam 20 kg/m³

rigid polyurethane foam 40 kg/m³

gypsum board (drywall) 700 kg/m³

Water — the float line 1,000 kg/m³

tungsten 19,250 kg/m³

gold 19,300 kg/m³

platinum 21,450 kg/m³

Water is 1,000 kg/m³. Anything below that floats.
Material	Density	Relative to water
rigid polyurethane foam	40 kg/m³	0.04×
expanded polystyrene foam	20 kg/m³	0.02×
air	1.2 kg/m³	0.00×
gypsum board (drywall) ←	700 kg/m³	0.70×
platinum	21,450 kg/m³	21.45×
gold	19,300 kg/m³	19.30×
tungsten	19,250 kg/m³	19.25×

Does it rust?

Gypsum board (drywall) contains no iron, so it cannot rust. Whether it degrades depends on the material, not on oxidation.

Is it magnetic?

Gypsum board (drywall) is not a metal and has no ferromagnetic response.

Common questions

What is the density of gypsum board (drywall)?: 700 kg/m³ (640–800), or 0.70 g/cm³.
Does gypsum board (drywall) float?: Yes. At 700 kg/m³ it is less dense than water's 1,000.
Is gypsum board (drywall) magnetic?: Gypsum board (drywall) is not a metal and has no ferromagnetic response.

Does gypsum board (drywall) float? Yes
Concrete 2,400 kg/m³
Brick 1,900 kg/m³
Tungsten carbide 14,900 kg/m³
Reinforced concrete 2,500 kg/m³
Graphite 2,200 kg/m³
Porcelain 2,400 kg/m³
Plaster 1,100 kg/m³
Silicon carbide 3,210 kg/m³

Sources

Typical range compiled from manufacturer specifications — At One Place

How these figures are compiled and checked