# Paint Quantity Calculator

Paint quantity calculator for any room, wall, or exterior. Returns gallons, liters, and order quantity with waste allowance. Handles interior, exterior, and masonry surfaces.

## What this calculates

The paint quantity you need is a simple function of paintable square footage, number of coats, and coverage rate. This paint quantity calculator handles all three plus standard deductions for doors and windows and a waste allowance for touch-ups, then tells you exactly how many gallons to order. Input either total wall square footage or room dimensions.

## Inputs

- **Input Method** — options: Total wall square footage, Room dimensions (L x W x H) — Pick the input method that matches what you know.
- **Total Wall Area** (sq ft) — min 0 — Only used when input method = area.
- **Room Length** (ft) — min 0
- **Room Width** (ft) — min 0
- **Ceiling Height** (ft) — min 0
- **Surface Type** — options: Interior smooth drywall (350 sq ft/gal), Exterior primed siding (300 sq ft/gal), Textured wall (250 sq ft/gal), Rough masonry / stucco (200 sq ft/gal), Ceiling flat paint (400 sq ft/gal)
- **Number of Coats** — min 1, max 5 — 2 coats is standard. Use 3 for dark-to-light color changes.
- **Doors to Subtract** — min 0, max 20 — Each standard door = 21 sq ft.
- **Windows to Subtract** — min 0, max 30 — Each standard window = 15 sq ft.
- **Waste Allowance** (%) — min 0, max 30 — 10% typical; 15% for complex cut-ins and trim work.
- **Price per Gallon** ($) — min 0

## Outputs

- **Gross Wall Area** (sq ft)
- **Paintable Area** (sq ft) — After door and window deductions
- **Paint Quantity (exact)** (gal)
- **Paint Quantity with Waste** (gal)
- **Gallons to Order** (gal) — Rounded up to whole gallons
- **Paint Quantity (liters)** (L)
- **Estimated Cost** — formatted as currency

## Details

## Paint Quantity Formula

The paint quantity formula every paint store teaches:

**Paint Quantity (gallons) = (Paintable Area x Coats) / Coverage Rate**

Coverage rate depends on the surface. Standard values published by Sherwin-Williams, Benjamin Moore, and Behr:

| Surface | Coverage per Gallon |
|---|---|
| Interior smooth drywall | 350 sq ft |
| Exterior primed siding | 300 sq ft |
| Textured wall | 250 sq ft |
| Rough masonry / stucco | 200 sq ft |
| Ceiling flat paint | 400 sq ft |
| Split-face block / brick | 150 sq ft |

## Paint Quantity by Input Method

This calculator accepts two input styles:

**Total wall square footage** is best when you already measured the room on a floor plan or walked the walls with a laser distance meter. Enter the number and go.

**Room dimensions** works when you just need the paint quantity for a standard rectangular room. Enter length, width, and ceiling height; the calculator computes perimeter x height as gross wall area, then subtracts openings.

## Example: 14x16 Master Bedroom

- Length 14 ft, width 16 ft, ceiling 8 ft
- Perimeter: (14+16+14+16) = 60 ft
- Gross wall area: 60 x 8 = 480 sq ft
- Openings: 1 door (21) + 2 windows (30) = 51 sq ft
- Paintable area: 480 - 51 = 429 sq ft
- Paint quantity: (429 x 2) / 350 = 2.45 gallons
- With 10% waste: 2.70 gallons
- **Order: 3 gallons**

Three gallons covers the room at 2 coats with a small amount left over for touch-ups.

## Paint Quantity for Common Rooms

| Room | Area | Gallons (2 coats, no openings) |
|---|---|---|
| 10 x 10 bedroom | 320 sq ft | 2 |
| 12 x 14 bedroom | 416 sq ft | 3 |
| 14 x 16 master | 480 sq ft | 3 |
| 16 x 20 living room | 576 sq ft | 4 |
| 10 x 14 kitchen | 384 sq ft | 3 |
| 8 x 12 bathroom | 320 sq ft | 2 |

## Paint Quantity for Exterior Jobs

A 2,000 sq ft two-story home has about 2,500-3,000 sq ft of exterior wall after deducting windows and doors. At 300 sq ft/gal and 2 coats:

- 2,750 x 2 = 5,500 sq ft total coverage
- 5,500 / 300 = 18.3 gallons
- With 10% waste: 20.2 gallons
- **Order: 21 gallons (four 5-gallon buckets plus one gallon)**

Buy one 5-gallon bucket at a time. Mix buckets in a clean tub before rolling to eliminate color-batch variation.

## Coverage Rate Corrections

Published coverage rates are achievable on ideal surfaces. Real-world paint quantity should account for:

- **New drywall:** 15-20% more paint; bare drywall is thirstier than primed or previously-painted
- **Rough cedar or redwood:** 20-30% more paint; grain soaks up primer and first coat
- **Stucco or split-face block:** double the smooth-wall quantity for the first coat
- **Cut-ins and trim:** add 1 extra gallon per 1,000 sq ft paintable area for brush work around edges

## Primer Is Separate Paint Quantity

Primer has its own coverage rate (200-300 sq ft/gal) and is calculated as a single extra coat. For new drywall or repaint projects where you are blocking stains, add a primer line item: paintable area / 250 = gallons of primer.

## Container Sizing

Paint retails in three US container sizes:

- **Quart (0.25 gal):** covers ~88 sq ft. For trim, touch-ups, or an accent wall under 40 sq ft.
- **1-gallon can:** covers 350 sq ft on smooth interior drywall. The default residential size.
- **5-gallon bucket:** covers 1,750 sq ft. Saves 20-30% per gallon vs 1-gallon cans.

Buy 5-gallon buckets whenever paint quantity is 3+ gallons. The per-gallon savings pays back a single bucket in one project.

## Paint Quantity Tips

- Always measure wall by wall, then add. For vaulted walls, break the shape into a rectangle plus a triangle (base x height / 2).
- Subtract only openings you are not painting. Trim and the inside face of doors are usually painted and should not be deducted.
- Round up to the nearest whole gallon, always. A half-gallon left over is worthless; a quart for touch-ups is gold.
- If you buy two brands or two runs of the same color, mix them in a 5-gallon bucket before rolling. This eliminates subtle color-batch variation that shows up under raking side-light.

## Frequently Asked Questions

**Q: How do I calculate paint quantity?**

A: Paint quantity formula: (Paintable Area x Coats) / Coverage Rate. Paintable area is gross wall area minus door (21 sq ft each) and window (15 sq ft each) openings. Coverage rate is 350 sq ft/gal for interior smooth drywall, 300 for exterior siding, 250 for textured, and 200 for masonry. Multiply paintable area by coats, divide by coverage, round up to whole gallons.

**Q: What is the paint quantity for a 12x14 room?**

A: A 12 x 14 room with 8 ft ceilings has 416 sq ft of gross wall area (perimeter 52 ft x 8 ft). Subtract 1 door (21 sq ft) and 2 windows (30 sq ft) = 365 sq ft paintable. At 350 sq ft/gal and 2 coats: (365 x 2) / 350 = 2.09 gallons. Add 10% waste, round up to 3 gallons. That's the paint quantity for a typical bedroom.

**Q: How much paint quantity for a 2,000 sq ft house interior?**

A: Wall area for a single-story 2,000 sq ft home is roughly 2,400-2,800 sq ft depending on ceiling height and interior layout. After deducting doors and windows, plan on 2,100-2,400 sq ft paintable. At 2 coats and 350 sq ft/gal: 12-14 gallons interior paint quantity. For the full house, add 4-6 gallons of ceiling paint and 2-3 gallons of trim paint.

**Q: What is the paint quantity per square foot?**

A: At standard interior coverage (350 sq ft/gal) and 2 coats, paint quantity per square foot of paintable wall area is about 0.006 gallons, or about 0.76 fluid ounces per sq ft. Stated differently: 1 gallon of interior paint covers 175 sq ft of wall at 2 coats, 1 gallon covers 350 sq ft at 1 coat.

**Q: Does paint quantity change for textured walls?**

A: Yes. Textured walls drop coverage from 350 to 250 sq ft/gal, meaning paint quantity increases 40%. Rough stucco or masonry drops to 200 sq ft/gal, increasing paint quantity 75% compared to smooth drywall. Split-face block drops to 150 sq ft/gal, more than doubling the paint quantity needed.

**Q: Should I add waste to my paint quantity?**

A: Yes, always. Add 10% waste for standard jobs, 15% for jobs with heavy cut-ins (trim around windows, doors, cabinets). The waste allowance covers spills, brushes, rollers left in paint, and end-of-job touch-ups. A full gallon or quart left over is perfect insurance against future scratches and nail holes.

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Source: https://vastcalc.com/calculators/construction/paint-quantity
Category: Construction
Last updated: 2026-04-08