Two rooms with the same floor area can need different amounts of paint. Height, the number of walls being painted, openings and ceiling work all change the surface area.
The Whatson Paint Calculator lets each room have its own wall counts. This is useful for a repaint where only part of the room is included, rather than automatically pricing all four walls.
Read the room row from left to right
Enter length, width and height in the selected measurement unit. Long wall count multiplies length × height; short wall count multiplies width × height. For a complete rectangular room, both counts are normally two.
The opening deduction stays in square feet. It is removed from the selected wall area. Optional ceiling area is then added from room length × width.
Ceiling inclusion is one setting for the entire calculation. If only some ceilings are being painted, run those rooms separately rather than including every room’s ceiling.
The result for one living room
Use a 12 × 10 ft room with 10 ft height, two long walls and two short walls. Deduct a 3 × 7 ft doorway by entering 21 sq ft. Include the ceiling.
The walls contribute 419 sq ft after deduction; the ceiling adds 120 sq ft. The total is 539 sq ft. With two coats, assumed coverage of 10 m² per litre per coat and 5% allowance, the checked requirement is 10.52 litres.
At 4 litres per container, buy three containers, containing 12 litres in total. The 10.52 litres is the estimated consumption; 12 litres is the rounded purchase.
Coverage belongs to the actual product
The 10 m² setting is an example assumption. Replace it with the intended paint’s stated coverage per coat and consider the substrate described in its instructions. A claimed combined coverage for two coats cannot be used as though it were per coat.
Container size is editable and can be a decimal. Enter the size printed on the product, not a rounded size from memory. Mixing different container sizes is outside this tool’s single size purchase calculation.
Separate the finish from the preparation
Primer, repairs, putty and labour are not included in the paint litres. Nor does an opening deduction account for trim paint that may use a different product.
The container rate produces a PKR cost for the rounded purchase. Check whether the quote is for the same finish, colour and size. For surface levelling quantities, use the Wall Putty Calculator with its own product consumption instead of treating putty as another paint coat.