How much does a sheet of 12.5mm plasterboard weigh?

A standard 12.5mm 1200×2400 board is roughly 19–23 kg, depending on brand and board type (density). Moisture, fire and acoustic boards of the same size weigh more.

When is a plasterboard a two-person lift?

As boards get thicker, denser and longer, weight rises fast — a 15mm dense acoustic board in a long length can exceed 50 kg. Heavy or awkward boards should be treated as two-person handling under HSE guidance.

Why do two brands quote different weights for similar boards?

Partly real differences, partly declaration basis: British Gypsum quote a minimum, Siniat a nominal mass, Knauf a weight. A fair comparison keeps track of which basis each figure is on.

Plasterboard weight: kg/m² and per board

How heavy is a plasterboard, and why do brands declare it differently?

Weight per square metre. Declaration bases differ by manufacturer — British Gypsum declare a minimum, Siniat a nominal mass, Knauf a weight. A value marked * is calculated by drywallDB (declared per-board weight ÷ nominal board area) because the manufacturer declares no kg/m² figure — it is not a manufacturer figure, and it inherits the nominal character of its inputs.

Weight looks like the simplest number on a data sheet and is quietly one of the most slippery: it drives manual handling, delivery and structural loading, yet the three UK manufacturers declare it on three different bases — so a fair cross-brand comparison has to know which basis it is reading.

kg/m² and per-board weight

Data sheets usually quote weight per square metre (kg/m²). The number that actually lands on someone’s shoulder is the per-board weight — kg/m² multiplied by the sheet’s nominal area. A standard 12.5mm 1200×2400 board covers 2.88 m², so at roughly 8 kg/m² it weighs about 19–23 kg depending on brand and type.

Heavier boards climb quickly. A 15mm dense acoustic board in a long length can exceed 50 kg — a genuine two-person lift, and a manual-handling consideration under HSE guidance, not just a logistics detail.

Why the declared basis differs

The three manufacturers do not declare weight the same way, and the difference is not rounding:

British Gypsum declare a minimum weight.
Siniat declare a nominal mass.
Knauf declare a weight.

Physical boards also vary within manufacturing tolerances, so two boards quoted at the same figure on different bases are not being measured identically. When a like-for-like weight is used as a proxy — for cost, for mass, for handling — that basis has to be carried along with the number, not dropped.

Declared vs calculated weight

Some data sheets declare a per-board weight directly; where they do not, it can be calculated from the declared kg/m² and the nominal area. drywallDB shows a declared figure verbatim with its citation, and marks any figure it has calculated itself with an asterisk — so you can always see which numbers are the manufacturer’s and which are drywallDB’s arithmetic over the manufacturer’s inputs.

That transparency matters most in a substitution, where a small weight delta is often the cost proxy that separates an over-specified alternative from a genuine like-for-like.

Frequently asked questions

How much does a sheet of 12.5mm plasterboard weigh?: A standard 12.5mm 1200×2400 board is roughly 19–23 kg, depending on brand and board type (density). Moisture, fire and acoustic boards of the same size weigh more.
When is a plasterboard a two-person lift?: As boards get thicker, denser and longer, weight rises fast — a 15mm dense acoustic board in a long length can exceed 50 kg. Heavy or awkward boards should be treated as two-person handling under HSE guidance.
Why do two brands quote different weights for similar boards?: Partly real differences, partly declaration basis: British Gypsum quote a minimum, Siniat a nominal mass, Knauf a weight. A fair comparison keeps track of which basis each figure is on.

Related guides

Rw — airborne sound insulation — What does the Rw number on a partition system mean?
EN 520 board types explained — What do EN 520 Type A, D, E, F, H, I, P and R mean?
Tapered edge vs square edge — TE or SE — which edge profile do I need?

This copy powers drywallDB’s in-app tooltips. The product behind it searches every UK plasterboard, compares cross-brand equivalents and cites every value to its manufacturer data sheet. Start free — 7 days, no card.