construction calculator

Paint Calculator

Estimate paint from room dimensions, coat count, and opening area so you can buy once and finish the job.

Important Use Notice

Planning calculator only. Do not rely on this page alone for structural design, permitting, code compliance, engineering signoff, procurement quantities, or contractual commitments.

Context

The calculator uses room perimeter and wall height, subtracts doors/windows area, then applies coats and coverage.

Estimate

Enter job values, review the estimate, then use the decision hints before ordering or quoting.

Estimate Results

Enter values to see the result.

Next Step

Bedroom repaint where doors and windows should be excluded
Quick store run check for liters and gallon equivalent
Scope check before contractor material order

Check

Using one wall length as if it were full room perimeter
Ignoring openings and overbuying paint

Reference

room Lengthroom Widthwall Heightcoatsliters
1210827
15129210

Example

Room 12×10 ft, wall 8 ft, openings 20 sq ft, 2 coats -> paintable area 332 sq ft -> total 664 sq ft -> 7 L
Room 15×12 ft, wall 9 ft, openings 30 sq ft, 2 coats -> paintable area 456 sq ft -> total 912 sq ft -> 10 L

Formula

Liters = ((2 × (Room Length + Room Width) × Wall Height - Openings Area) × Coats) / 100

100 sq ft per liter is used as a practical planning value for interior wall coverage.

Round up the final value. Coverage differs by brand, finish, and surface texture.

Next Step

Next Calc

Drywall Calculator

Estimate 4×8 drywall sheets for a room or wall so you can plan coverage, cuts, and a small waste allowance.

Next Calc

Wallpaper Calculator

Estimate wallpaper rolls for a room, including a planning allowance for pattern repeat and waste.

Next Calc

Flooring Calculator

Estimate boxes of laminate, vinyl, or tile needed for a room so you can plan coverage and waste more realistically.

System note: validate this estimate against local code and supplier requirements before ordering.

FAQ

How many coats do I really need?

2 coats for most colors. Dark-to-light change may need 3.

What about ceiling paint?

Calculate ceiling area separately (same length × width).