Wall, paint and plasterboard calculators

Which wall calculator do I need?

Decide whether you are building the wall, lining it or finishing it. Building a masonry wall is a count of units and mortar. Lining a framed wall is a count of sheets plus the fixings and joint materials that go with them. Finishing is paint or paper, and both depend on the surface you finish more than on the room size alone.

All four tools take the same measurements: the length of each wall, its height and the openings in it. What you do with the openings differs. Paint and plasterboard counts usually subtract large doors and windows. Wallpaper makers often tell you not to, and brick counts subtract openings and then add back the extra for cut bricks around them. The table shows which tool answers which job.

Wall and paint pages

How far does a gallon or litre of paint go?

Less far than the biggest number on the tin, and the spread between products is wide. Coverage is quoted per coat at the film thickness the maker tested for, and it falls on rough, porous or new surfaces. The table lists what several makers publish. Note that the UK figures are maximums, given as "up to", while US data sheets usually give a range.

Two coats is the normal system on both sides of the Atlantic. Sherwin-Williams specifies 2 topcoats on drywall, either self-primed or over 1 coat of primer. Dulux Trade's normal finishing system is 2 full coats; 1 may do on sound, similar-colour paintwork. Texture matters even more than the number of coats. Dulux Trade Weathershield Smooth Masonry covers 4-6 m2/L on textured surfaces such as pebbledash. Gallons and litres also differ by more than people think: One US gallon is 3.785412 litres. The measuring walls, ceiling and trim guide shows how to get the area that these figures divide into.

What sheet, brick and roll sizes do the calculators assume?

The ones the main makers sell, in both markets. For framed walls the US default is a four-foot-wide sheet. Standard US gypsum panels are 4 ft (48 in, 1219 mm) wide; USG also lists a 54 in width for UltraLight panels. 4x8, 4x10 and 4x12 ft sheets are the sizes National Gypsum uses in its per-area estimating table. UK board is metric throughout. The standard UK plasterboard sheet is 1200 x 2400 mm, made by both British Gypsum and Knauf. UK standard wallboard is sold in 9.5, 12.5 and 15 mm thicknesses. National Gypsum's planning table gives a quick cross-check for large jobs: National Gypsum estimates 32 4x8, 25 4x10 or 21 4x12 sheets per 1,000 sq ft. It also covers finishing. Paper joint tape use is about 350-370 ft (107-113 m) per 1,000 sq ft of board. About 9 US gallons (34 L) of ready-mixed all-purpose joint compound finishes 1,000 sq ft (93 m2) of board.

Bricks differ more between markets than sheets do. A US modular brick is nominally 4 x 2 2/3 x 8 in (102 x 68 x 203 mm), sized so three courses equal 8 in. The standard UK brick is 215 x 102.5 x 65 mm. About 60 standard UK bricks are needed per square metre of half-brick (stretcher bond) wall. Both counts are for a single skin, before breakage. Add at least 5% to net brick quantities for breakage and waste. The brick quantity for gables and openings guide works through walls that are not plain rectangles.

Wallpaper rolls look alike in both markets but are not quite the same. A 20.5 in x 33 ft roll covers about 56.4 sq ft (5.24 m2) before pattern and trimming waste. The common UK/European roll is 0.53 m wide x 10.05 m long. The usable area is lower than either figure once each strip is matched to the next. Wallpaper comes in free, straight or offset (drop) match; offset match wastes more per strip. Read pattern repeat and drop matching before ordering a bold print.

Should I subtract doors and windows?

It depends on the material, and the common habit of always subtracting them is wrong for wallpaper. Graham & Brown recommends not deducting doors and windows, so the excess acts as a margin. Graham & Brown advises allowing an extra 10% for waste and mistakes. The leftover from around openings is what covers the pattern match and the odd mis-cut strip.

For paint, the calculator subtracts whatever openings you enter. Entering only the large ones, such as patio doors, leaves a small margin for cutting in around the rest. For plasterboard, an offcut from a window opening is often too small or the wrong shape to reuse, so counting sheets as if the wall were solid is the cautious choice. For brick, subtract the opening and then allow for the cut bricks at the reveals; that is the extra the brick calculator adds.

What do the data say about walls and wall materials?

On new US houses brick is now a minority finish. Brick was the primary exterior wall on 16% of new US single-family homes completed in 2025, down from 20% in 2023 and 35% in 1973 (Census Bureau, Characteristics of New Housing). Vinyl siding and stucco were each the primary exterior wall material on 26% of new US single-family homes completed in 2025, ahead of fiber cement (23%) and brick (16%), per the Census Bureau. These shares describe the main exterior wall material on newly completed single-family homes, not the existing housing stock.

Indoors, drywall has become one of the steepest price rises among building materials. US producer prices for gypsum products, which include drywall, were 51.8% above the 2020 average in September 2026, the highest reading since at least 2019, and 1.4% up on a year earlier (BLS PPI). A producer price index tracks what manufacturers charge, not the shelf price, but it shows why a sheet count worth getting right is worth a second check. In the UK, wallpaper has gone the other way. UK manufacturers sold £73.2 million of wallpaper and similar wall coverings in 2025, down from a peak of £136.4 million in 2021 (−46%), per ONS Prodcom (product 17241100; 2025 figures provisional). That is a value of factory sales, not of rolls hung.

The building material price index page carries the full price series, and the jobsite waste data page shows how much drywall and brick end up as debris.

Where do the wall calculators stop?

They count finishes and units for a wall that is already designed. They do not decide stud spacing, fire ratings or whether a brick wall needs a structural design. Stud spacing does affect fixings, though, and code sets the limits. On walls framed at 16 in on centre, screws for 1/2 or 5/8 in board go at most 16 in (406 mm) apart without adhesive. On walls framed at 24 in on centre, IRC limits screw spacing to 12 in (305 mm) for 1/2 and 5/8 in board without adhesive. Where a fire-rated board is required, the code names it. 5/8 in (15.9 mm) is the Type X fire-rated thickness; the IRC requires 5/8 in Type X on garage ceilings beneath habitable rooms.

Paint calculators assume a sound, primed surface. Bare plaster, patched board or a strong colour change can need an extra coat that no area formula predicts. Free-standing brick walls, retaining walls and anything carrying a load need local code checks or an engineer, not a quantity tool.

Every number here comes from a code, a standard or a maker's data sheet, listed in the sources below. Read our calculation methodology for how conflicts are handled. Walls often come with insulation: see the thermal insulation category. Floors are in the square footage for flooring section.

Wall calculator questions