The practical toolbox
Paint calculator for walls & ceilings
Work out how many litres of paint to buy for your rooms. Build the room shapes, deduct doors and windows, and use your paint label’s coverage to estimate coats and whole tins.
Save this version with its URL. Bookmark this page or copy its link to reopen your inputs later. Save a new link after making changes. Anyone with the link can read your inputs. Results are recalculated on reopening; print a copy if you need a fixed record.
Create a saved link with AI
Give your AI assistant your measurements or figures and the instructions below. It can create a ready-to-open link for this paint estimate. Open the link, check the inputs, then bookmark it or copy the URL to reuse it later.
Copy this prompt and add your information:
Read https://www.lejnel.com/paint-quantity-url-guide.txt and generate a clickable saved-plan URL for my paint estimate. Convert my units to the guide’s required units. Ask for missing inputs instead of guessing, and explain any assumptions. Return the link and a summary of the inputs used.
Read the URL format and examples · AI instructions for all tools
The URL contains your inputs. Anyone with the link can read them. Future calculator updates may change results; retain a printed copy when you need a fixed record.
Your paint estimate
Each room outline follows its joined sections. Walls are numbered to match the length list. Solid outlines show walls; dotted dimensions show overall edge-to-edge size. Printed diagrams are not full-size templates.
Ceiling uses the same product, coverage and coats. Calculate a different ceiling paint separately. Excludes trim, primer and sloped surfaces.
How much paint do I need?
Divide your paintable wall and ceiling area by the coverage on your paint label, multiply by the number of coats, then add your chosen extra allowance. This free paint calculator does the area calculation for rectangular, L-shaped and stepped rooms and rounds the result up to whole tins. It estimates quantity for one paint product at a time.
How to measure a room for paint
- Build the room outline. Enter the first section’s across and depth measurements. For an alcove, L-shape or stepped room, select a section and use an arrow to add another rectangle. Resize it or drag it to snap onto a valid edge. Use wall-to-wall measurements.
- Enter the wall height and openings. Use one height for each room. Add together the width × height of doors, windows and other surfaces you will leave unpainted, and enter that area for the room.
- Choose walls only or walls and ceiling. Include a flat ceiling only if it uses the same paint and coat count. Add separate rooms for spaces divided by walls; shared edges between sections of one open room are not counted as walls.
- Read your paint label. Enter coverage in square metres per litre per coat, the required number of coats and your tin size. Choose an extra allowance for the job.
- Review the shopping estimate. Check each room’s numbered walls and area breakdown, then the combined litres, whole tins and estimated leftover. Copy the estimate link or print it before shopping.
Wall paint and ceiling paint formulas
- Net wall area
- Exposed wall perimeter × wall height − unpainted opening area.
- Flat ceiling area
- Sum of the non-overlapping rectangular section areas for each included ceiling.
- Paint including allowance
- (Total paintable area × coats ÷ coverage per litre) × (1 + allowance ÷ 100).
- Whole tins to buy
- Round the required litres ÷ tin size up to the next whole tin.
The calculator removes shared section edges before measuring the perimeter. Separate rooms each include their own face of dividing walls. All rooms share one paint specification; use separate estimates when products or coat requirements differ.
Worked examples: paint litres for a room
These examples use a 2.4 m wall height, 4 m² of unpainted openings, two coats, an illustrative coverage of 10 m² per litre per coat, a 10% extra allowance and 2.5-litre tins. These are calculation examples, not product specifications.
| Room and surfaces | Paintable area | Litres with allowance | Whole tins |
|---|---|---|---|
| 4 × 3 m room, walls only | 29.6 m² | 6.512 litres | 3 × 2.5 litres |
| 4 × 3 m room, walls and ceiling | 41.6 m² | 9.152 litres | 4 × 2.5 litres |
| L-shaped room, walls and ceiling | 54.2 m² | 11.924 litres | 5 × 2.5 litres |
The rectangular room has a 14 m wall perimeter: 14 × 2.4 − 4 = 29.6 m² of walls. Its ceiling adds 12 m². The L-shaped example joins a 2 × 1.5 m section to the right side of the 4 × 3 m section, aligned at the top. Its 1.5 m shared join is excluded from the wall perimeter, leaving an 18 m perimeter and 15 m² ceiling: (18 × 2.4 − 4) + 15 = 54.2 m².
Check the paint label before buying
Use the coverage, substrate suitability, preparation and required coats for your chosen paint. Defaults are illustrative, not verified product requirements. Surface condition and application can change consumption. The allowance is your choice, not a guaranteed waste rate. This estimate excludes primer, trim and separate door paint.
For preparation and the order of work, read how to paint a room. If you are also changing the floor, use the vinyl and laminate flooring layout planner to work out board cuts and packs.
Paint calculator questions
How do I calculate how much paint I need for a room?
Multiply the room’s exposed wall perimeter by its height, then subtract unpainted doors and windows. Add the ceiling area if you will use the same paint on it. Multiply the total area by your coat count, divide by the paint label’s coverage per litre, add your chosen allowance, then round up to whole tins.
How much wall area does 5 litres of paint cover?
It depends on your product’s coverage and the number of coats. At an illustrative 10 square metres per litre per coat, 5 litres covers 50 square metres once, or 25 square metres with two coats, before any extra allowance. A 2.5-litre tin at that same example rate covers 12.5 square metres with two coats. Use your actual paint label rather than these example rates.
How do I calculate paint for an L-shaped room?
Add edge-connected rectangular sections until the sketch matches your room. The calculator counts the exposed outline as walls and excludes joins between sections. It uses the combined section area for a selected flat ceiling, rather than the surrounding bounding rectangle.
Should I subtract doors and windows from the paint area?
Enter the total area you will leave unpainted for each room. Do not deduct doors or reveals that will use the same paint. Deduct the relevant opening on each painted side of a doorway when calculating separate rooms.
Can I calculate wall paint and ceiling paint separately?
Yes. Leave the ceiling excluded for a wall-only estimate. Include it only when the same paint, coverage and coat count apply. For a different ceiling product, calculate its area from the room diagram and use that product’s coverage and coat requirements separately; this tool does not have a ceiling-only mode.
How much extra paint should I allow?
Enter the percentage you want to reserve for application losses or touch-ups. The default 10% is an editable example, not a product recommendation or guarantee. Wall condition, application and the job’s scope affect what you need; check your product guidance.
Can I measure the room in feet?
Yes. Select Imperial for decimal-foot room dimensions and wall height. Saved dimensions remain in metres. Opening area is entered in square metres and paint quantities in litres in either display mode; gallons are not used.
Can I estimate several rooms and save the result?
Add up to 12 rooms with individual shapes, wall heights, openings and ceiling selections. They share one paint, coverage, coat count and tin size. The calculator adds their paint requirements before rounding to tins. Copy the estimate link or bookmark the complete URL to reopen the inputs; print a copy for a fixed record.
Limitations and responsibility
This estimate supports 1–12 separate rooms, each with 1–6 edge-connected, non-overlapping rectangular sections, vertical walls of one height per room, and an optional flat ceiling. Shaped rooms must fit within 20 × 20 m; each section must be 0.3–20 m in both directions. Single rectangles support 0.1–100 m to preserve older saved estimates. No sloped walls, diagonal walls, internal partitions, or automatic doorway deductions are modelled. Each separate room includes its own face of shared dividing walls. Join rectangles only within a single open room. It does not select paint or specify preparation, drying times or safety procedures. Independently verify inputs and quantities before purchase or work. Results may contain errors. To the extent permitted by law, lejnel.com disclaims warranties and liability for wasted materials, costs and damage resulting from use. Statutory rights remain unaffected. See Terms of Use.
Continue with the flooring planner, gallery wall planner or all tools.