Paint Calculator

A paint calculator turns wall dimensions into an estimated coating volume. This tool multiplies wall length by wall height and by the number of similar walls, then subtracts the combined area of doors, windows, and other surfaces that will not be painted. It multiplies the remaining paintable area by the number of coats and divides by the product coverage rate in square meters per liter. The result is the theoretical liters required before an allowance for waste and touch-ups. Coverage varies considerably between products and surfaces. Smooth, sealed drywall may approach the rate printed on the can, while porous masonry, fresh plaster, textured walls, rough timber, and dramatic color changes can consume more paint. Use the manufacturer value for the exact product and application method. Primer and finish paint normally have different coverage rates and should be estimated separately. If several rooms or wall heights differ, calculate each group and add the results. Measure along the actual wall faces rather than using floor area. For equal walls, the Number of Walls field provides a quick multiplier. For a mixed room, calculate one wall group at a time or enter an equivalent total length with one wall. Subtract openings only when their combined area is significant. Small openings can be left in the estimate because paint used around reveals, edges, brushes, rollers, and trays often offsets the apparent saving. The number of coats should reflect the complete specification. Two finish coats are common, but a well-matched repaint may cover sooner and a strong color transition may need an additional coat. Do not count primer as finish paint unless one product is explicitly designed and rated for both functions. Round the calculated volume up to available container sizes and keep enough matching batch paint for repairs. This estimate supports budgeting and purchasing but cannot predict every site condition. Application loss depends on roller nap, brush technique, spray transfer efficiency, masking, mixing, and leftover paint in containers. A reserve of roughly five to fifteen percent is often practical, with more for rough or highly absorbent surfaces. Confirm moisture conditions, preparation, drying times, and compatible primers before work begins. Proper cleaning, filling, sanding, and sealing usually improve both real coverage and the quality of the finished surface.