Paint Calculator — Fast, Accurate Paint Estimates for Every Project

Planning a paint job? Use the BritishInterior.com Paint Calculator — a simple, reliable paint estimator that tells you how much paint do I need in seconds. Whether you’re doing an interior bedroom, an exterior façade, a fence, or a deck, this paint coverage calculator converts your room and wall measurements into the exact gallons of paint or liters of paint you should buy.

Our room paint calculator handles metric and imperial units, so you can enter metres or feet and get accurate results. Add walls, ceilings, and floors, then subtract doors and windows to produce a true paint quantity calculator output. Choose the number of coats, factor in primer, and the tool adjusts coverage per gallon for different surfaces: drywall, plaster, masonry, stucco, wood, metal, and rough decking all behave differently — our estimator lets you set realistic coverage rates.

Why this paint estimator saves time and money

Manually calculating paint needed often leads to overbuying or running out mid-job. The wall paint calculator and ceiling paint calculator on BritishInterior.com eliminate guesswork. Want an interior paint calculator for living rooms and bedrooms? Or an exterior paint calculator for rendered walls and stucco? This single tool does both, giving you total paint required and an optional paint cost calculator so you can budget by price per gallon or per litre.

How to use the paint calculator (3 easy steps)

1. Measure each wall and the ceiling, entering dimensions in metric or imperial.

2. Enter doors and windows to subtract non-paintable areas. Include trim and baseboards if you plan to paint them.

3. Select surface type and finish (eggshell, satin, matte, or semi-gloss), number of coats, and whether you’ll use latex, oil-based, or emulsion paint. The calculator then shows paint needed by gallons or liters and a cost estimate.

Real-world accuracy

Coverage per gallon is affected by texture and finish. Smooth plaster or emulsion often yields higher coverage than rough masonry or textured stucco. If you’re switching from a dark colour to a pale one, add a primer coat in the calculator — primer reduces the total number of finish coats and improves coverage. For decks and fences, the deck paint calculator and fence paint calculator modes adjust for horizontal surfaces and increased absorption.

Pro tips for best results

• Add 10%–15% extra for touch-ups and future repairs.

• Use the paint cost calculator to compare brands and finishes by price per gallon or per litre.

• For trim, doors, and windows, choose semi-gloss or satin for durability — the paint estimator will factor different coverage rates.

• New wood or porous floors and fences may require primer; set the primer option to get realistic paint quantities.

Built for every project

This paint quantity calculator works for single rooms, whole-house repaints, or specialty tasks like painting a floor or a decorative feature wall. Choose imperial or metric units, set your preferred coverage per gallon, and get a precise answer to how much paint do I need — no complicated math required.

Ready to plan with confidence? Try the BritishInterior.com Paint Calculator now to get a fast, budget-aware paint estimate — gallons or liters, interior or exterior, one coat or two. Paint smarter, buy exactly what you need, and spend less time in the store and more time finishing your project.