Paint calculator

How to use this paint calculator

Enter the room size, the doors and windows, the number of coats and your paint's coverage. The calculator shows the paintable area, the litres you need and how many cans that comes to.

Inputs: room size, doors, windows, coats

Use metres for every measurement.

• Room size. The room's length, width and height in metres, or a wall area in square metres if you already know it.
• Ceiling. Choose yes to include the ceiling, or no for walls only.
• Doors and windows. How many there are and the size of each, as width x height in metres. The calculator subtracts them from the wall area.
• Coats. The default is 2 coats.
• Coverage. Nippon Odour-less All-in-1 at 10 to 12 square metres per litre, Nippon EasyWash & Clean Matt at about 13 square metres per litre, or your own paint's figure from its data sheet.

To measure a door, take the full width of the frame, then the height from the floor to the upper edge of the frame. Measure a window the same way: the full width of the frame, then from its lower edge to its upper edge. Measure the room's length and width along the floor, and the height from floor to ceiling.

Result in litres and cans

This is a paint litres calculator first, so the main figure is in litres. You get:

• Paintable area in square metres, after doors and windows are taken off.
• Litres needed, worked out as area x coats / coverage. For a paint with a coverage range, you see two figures: one at the higher coverage (fewer litres) and one at the lower coverage (more litres).
• Cans, with the litres rounded up into 5 litre and 1 litre cans, or into 5 litre cans only.

Here is a short worked example using a made-up room: 4.5 metres long, 3.5 metres wide and 2.75 metres high, with one door, one window and no ceiling.

So this example room needs 6.7 to 8 litres for 2 coats. For 8 litres, that is one 5 litre can and three 1 litre cans, or two 5 litre cans.

How the calculation works (method and sources)

Like any how much paint calculator, this one rests on two numbers: the area you paint and how far a litre goes.

• Walls: 2 x (length + width) x height, minus doors and windows.
• Ceiling, if included: length x width.
• Litres: area x coats / coverage per litre.

For Odour-less All-in-1, Nippon lists a theoretical coverage of 10 to 12 square metres per litre by roller or brush, and an overcoating time of 2 hours minimum. Its technical data sheet recommends 1 coat of sealer and 2 coats of the paint, and lists 1 litre and 5 litre packs. The product page also shows Nippon's own estimated cans by HDB room type, which you can compare with your result.

For EasyWash & Clean (Matt), Nippon lists a theoretical coverage of approximately 13 square metres per litre at 30 microns dry film thickness, by roller, brush or spray.

These are the makers' theoretical figures. Real coverage is usually lower on rough or porous walls, so the calculator rounds up.

Limits of this calculator

The result is a planning figure, not an exact count.

• Theoretical coverage. Nippon says the number of cans may vary with the way you paint.
• Preparation is not included. Sealer, primer, putty and repairs are not part of the result. If a wall has mould, read about painting over mould first, and see mould on the ceiling for ceilings.
• No prices. The cost depends on the job. For labour, see handyman rates.

Before you paint

Look at the walls first. HDB explains that cracks along joints between block walls and concrete form because different materials expand and contract with temperature changes. For hairline cracks, HDB says to re-paint the wall with a flexible sealant or elastomeric paint. For wider cracks, engage a contractor. HDB's preventive measures are cross-ventilation in the flat and re-painting the walls regularly.

Check the ceilings too. HDB says spalling concrete is common in older buildings, especially in damp areas such as kitchens and toilets, and the home owner is responsible for preventing it through regular maintenance. Prevention includes painting ceilings regularly, sealing cracks and unused drilled holes, and opening windows, vents or doors to reduce humidity in kitchens, toilets and bathrooms.

Keep your painting inside your flat. HDB lists painting external parts of the building, such as common corridor walls and ceilings, as disallowed building works. If you paint yourself, HDB asks residents to keep DIY works to 7am to 10.30pm and keep noise to a minimum.

To hand the job over, compare painting services, or read handyman or painting contractor to decide who suits it. For small fixes before painting, see handyman services.

Questions