Room area
For each rectangular room, Paintwise estimates wall area as perimeter × height. Ceiling area is length × width. The calculator deducts standard openings when you enter doors and windows. Because real opening sizes vary, inspect the result and use manual coverage when accuracy matters.
Paint quantity
Paintable area is multiplied by the chosen number of coats, then divided by the coverage figure. Paintwise applies a 10% planning buffer to help account for cutting-in, uneven absorption, touch-ups and small measurement errors. The exact paint label always takes priority.
Multiple products and rooms
Rooms are totalled in the selected unit system. When you add separate products—for example primer, ceiling paint and wall paint—each product can use its own coverage and price. This prevents a high-coverage wall paint from being used to estimate a specialty primer.
Can-size suggestions and supplies
The can-size helper compares typical purchase sizes to the calculated quantity. It is a purchasing guide, not stock availability. The supply list suggests commonly needed tools based on room and paint choices; it does not diagnose surface problems or replace professional advice.
Paintwise is a planning tool. It does not assess moisture, lead paint, ventilation, surface compatibility, building regulations or the structural condition of a property.