How much paint for a 10 × 12 room?

Measure every surface

Confirm whether 10 × 12 is feet or metres, then measure wall height. Add the ceiling only when it will be painted.

Subtract openings

Subtract measured door and window area from the gross wall and ceiling area.

Use product coverage and coats

Enter the coverage from the paint data sheet for the surface and application method, then apply the planned number of coats and visible wastage.

Worked wall-area example

Assume the room is 10 ft × 12 ft with an 8 ft wall height. Gross wall area is perimeter × height = 2 × (10 + 12) × 8 = 352 sq ft. If one door and windows total 50 sq ft, net wall area is 302 sq ft. A ceiling would add 120 sq ft only if it is included in the work.

Turn area into litres

If the selected product sheet states an applicable coverage of 100 sq ft per litre per coat, two coats on 302 sq ft require 302 × 2 ÷ 100 = 6.04 litres before wastage or pack rounding. The 100 sq ft value is an example input, not a universal paint rating; substrate and application conditions must match the product information.

Surface condition matters

New plaster, porous repairs, dark-to-light colour changes, texture and application method can change primer and paint use. Follow the selected system’s preparation, primer, dilution, drying and coverage guidance. Do not hide uncertainty by adding an unexplained large wastage value.

Separate colours and products

Calculate walls, ceiling, trim and accent surfaces separately when they use different products or colours. A combined litre total cannot be rounded sensibly if each paint comes in separate pack sizes. Keep primer outside the finish-coat total unless the product system explicitly combines them.

Check before ordering

Re-measure openings and height, confirm the unit, coats and product coverage, then round to available pack sizes. Supplier tinting and return rules may affect how conservatively you buy. The calculator estimates quantity and does not rate brands or guarantee finish.

Room-paint measurement sheet

Record the room unit, all four wall lengths, height, each opening, ceiling inclusion, number of coats, primer treatment, product coverage, application method, wastage and pack sizes. Separate products and colours into different rows. This gives a painter or supplier something specific to correct and lets you update only the changed assumption instead of accepting an unexplained litres-per-room shortcut.

• Use coverage for the chosen product and surface.
• Do not count openings or ceiling twice.
• Round by product pack only after the net calculation.