Paint Calculator

What Is a Paint Calculator?

This free paint calculator tells you exactly how many litres of paint to buy for any room. It accounts for wall area, ceiling height, number of coats, paint coverage rate, door and window deductions, and automatically adds a 10% waste buffer. In short, this paint calculator means you buy the right amount first time — no costly extra trips to the hardware store, and no risk of running out with a discontinued colour.

Guessing paint quantities is surprisingly easy to get wrong. Too little and you run out mid-wall. Too much and you waste money. Furthermore, paint colours from different production batches often have subtle variations — making a second order potentially impossible to match exactly. This paint calculator solves all of these problems.

How Does the Paint Calculator Work?

For example, a 4 m × 3.5 m room with 2.4 m ceilings, one door and one window, painted with 2 coats at 12 m²/L: wall area = (2 × 7.5 × 2.4) − 3.5 = 32.5 m². Paint needed = 32.5 × 2 ÷ 12 × 1.1 = 5.96 L. This paint calculator rounds up and recommends buying 6 litres.

How to Use This Paint Calculator

1. Enter room length and width in metres.
2. Enter ceiling height — 2.4 m is standard in most Australian homes. Adjust for older high-ceiling properties.
3. Select number of coats — 2 coats is standard for most painting jobs.
4. Enter paint coverage rate — check the label on your specific paint tin. Default 12 m²/L is typical for interior wall paint.
5. Select doors and windows — the paint calculator deducts these from your total wall area.
6. Click Calculate — litres needed including a 10% buffer appear instantly.

What Does the 10% Buffer in This Paint Calculator Mean?

This paint calculator adds 10% to the calculated amount to account for drips, roller nap absorption, uneven surfaces, touch-ups after the job, and small measurement inaccuracies. Never buy the exact minimum this paint calculator shows — always round up to the next available tin size. Leftover paint stored in a well-sealed tin can be kept for years for future touch-ups.

Is This Paint Calculator Accurate?

This paint calculator is accurate for standard rectangular rooms. For unusual shapes, arches, or built-in wardrobes, calculate each wall section separately and add the results. According to Dulux’s paint quantity guide, coverage rates vary significantly between product types — always use your specific product’s rate in this paint calculator for the most accurate result.

Paint Calculator for Different Room Types

• Bedroom: Standard 4 m × 3.5 m room with 2.4 m ceiling needs approximately 5–6 L for 2 coats.
• Living room: Larger rooms with more doors and windows — use this paint calculator with actual measurements for accuracy.
• Bathroom: Select semi-gloss or gloss paint; coverage rates are lower. Adjust the coverage field in this paint calculator accordingly.
• Ceiling only: Enter room length × width as Length × Width and set height to 1 m — this paint calculator works for any flat surface.

Paint Calculator — Frequently Asked Questions