Paint for 300 Sq Ft - How Many Gallons Do You Need?

The wall is half done and the can is empty

Running out of paint mid-project means a second trip to the store, a potential color mismatch between batches, and wasted time. This calculator takes four inputs - area, paint type, number of coats and safety margin - and returns the exact number of gallons to buy. Add a price per gallon and it shows total material cost too.

A 400 sq ft room (typical 12x14 ft with 8 ft ceilings) with 2 coats of latex paint and a 10% margin needs about 2.3 gallons - so you buy 3 gallons. At $35/gallon that is $105 in paint. The leftover covers touch-ups for years.

How to use - step by step

Area to paint - measure each wall (height x width) and add them up. Subtract windows and doors for precision. A 12x14 ft room with 8 ft ceilings has about 416 sq ft of wall.
Paint type - latex is the most popular and easiest to clean. Oil-based covers more per gallon but needs mineral spirits. Acrylic is more durable for high-traffic areas.
Number of coats - 2 coats is standard. Use 3 when changing from dark to light or covering stains.
Safety margin - 10% for smooth drywall. 15-20% for textured, brick or rough surfaces.
Price per gallon (optional) - enter to get total cost and cost per square foot.
Read results - gallons needed, coverage comparison across 5 paint types, and cost breakdown.

Coverage rates by paint type

Paint type	Coverage (sq ft/gal)	Best for	Cleanup
Latex	350-400	Walls, ceilings	Water
Acrylic	300-350	High-traffic, exteriors	Water
Emulsion	350-400	Budget projects	Water
Oil-based	400-450	Trim, doors, cabinets	Mineral spirits
Chalk	350-400	Furniture, decorative	Water

The problem - and how the calculator solves it

The problem

You guess how much paint you need. You buy 2 gallons. Halfway through the second coat the roller starts dragging. The store is closed. Tomorrow you get a new can from a different batch - and the color is slightly off. Every painter has this story.

The solution

Measure the area. Enter paint type and coats. Add a margin for texture and waste. Buy the exact number of gallons - rounded up. The leftover is your touch-up reserve. One trip. One batch. One consistent color on every wall.

How much does surface texture affect paint usage?

Surface type	Extra paint needed	Recommended margin
Smooth drywall (painted)	0%	5-10%
New drywall (primed)	+5-10%	10-15%
Light texture (orange peel)	+10-15%	15%
Heavy texture (knockdown)	+15-25%	20%
Brick or stucco	+20-35%	20%
Bare wood (unprimed)	+25-40%	20%

Practical examples

Example 1: Small bedroom - 300 sq ft walls, latex, 2 coats, 10% margin
Need: 1.8 gal - buy 2 gallons. At $35/gal = $70

Example 2: Living room - 600 sq ft walls, acrylic, 2 coats, 10% margin
Need: 4.1 gal - buy 5 gallons. At $45/gal = $225

Example 3: Entire house interior - 2,400 sq ft, latex, 2 coats, 15% margin
Need: 14.7 gal - buy 15 gallons (3 x 5-gal bucket). At $30/gal = $450

Example 4: Kitchen cabinets - 80 sq ft, oil-based, 3 coats, 15% margin
Need: 0.6 gal - buy 1 gallon. At $55/gal = $55

Example 5: Color change (dark to light) - 500 sq ft, latex, 3 coats, 10% margin
Need: 4.4 gal - buy 5 gallons. At $40/gal = $200

FAQ - Frequently asked questions

How much does one gallon of paint cover?

One gallon covers 350-400 sq ft on smooth, previously painted drywall. That is roughly the walls of a 10x12 ft room with 8 ft ceilings (one coat). Textured surfaces, bare wood or brick can reduce coverage by 20-40%.

Do I need a primer coat?

Use primer on: bare drywall, bare wood, stains you want to block, and when going from very dark to very light. Modern paint-and-primer combos reduce the need, but a dedicated primer still gives better adhesion and color accuracy. Primer is a separate purchase - this calculator covers topcoat only.

Is expensive paint worth it?

Generally yes. Premium paints ($50-80/gal) have higher pigment concentration, which means better coverage in fewer coats, better washability, and longer life. A $70 gallon that covers in one coat can be cheaper than two coats of $30 paint - and the result looks better. The cost difference over a whole room is often just $50-100.

How do I calculate wall area for a room?

Measure the perimeter (sum of all wall lengths) and multiply by ceiling height. Example: a 12x14 ft room has a perimeter of 52 ft. At 8 ft ceilings: 52 x 8 = 416 sq ft. Subtract windows (~15 sq ft each) and doors (~20 sq ft each) for a more precise number.

Roller vs brush vs sprayer - does it affect paint usage?

Yes. A roller uses the least paint and gives even coverage. A brush uses 10-15% more due to thicker application but is needed for edges and trim. A sprayer uses 20-30% more because of overspray - but covers large areas much faster. For whole rooms, roll the walls and brush the edges.

Should I buy one big bucket or several small cans?

If you need 4+ gallons of the same color, buy a 5-gallon bucket. It is 15-25% cheaper per gallon than individual cans, and - critically - all the paint comes from the same batch so there is zero color variation. For smaller jobs, single gallons are fine. Always buy from the same batch number.

Related tools

House Building Cost Calculator

Estimate total build cost by construction type, finish level and region. Materials vs labor split and 9-cell comparison - See calculator

How much paint do you need for 300 sq ft of wall?

Parameters