Number of coats
Every additional coat repeats the full surface area. Two coats need roughly twice the paint of one coat.
Choosing Your Paint
How Much Paint Will I Need?
Estimate how many 400ml aerosols you need from the area, number of coats and an allowance for overspray, edges and application losses. For planning, one aerosol is treated as covering approximately 1.5m² for one coat.
Plan the area, coats and real-world application allowance
Coverage is an estimate, not a fixed guarantee
The 1.5m² figure is a useful planning rate for one coat from one 400ml aerosol. Actual coverage changes with surface texture, shape, colour change, coat thickness, spraying distance, overspray and the number of test passes.
Calculate each coating layer separately and round up to complete cans. When the project is complex or appearance is critical, include a sensible allowance so the final coat is not interrupted.
400ml aerosol quantity estimator
How many aerosols do I need?
Enter the total surface area, choose the number of coats and add an allowance for real-world application losses.
Why coverage changes
Factors that affect how much paint you will use
The theoretical calculation is only the starting point. Project shape, surface condition and application losses determine the realistic quantity.
Surface texture and porosity
Rough, porous or absorbent surfaces usually use more paint than smooth sealed panels.
Edges, profiles and recesses
Frames, railings, mesh, curves and detailed shapes create more overspray and application loss than flat panels.
Colour change and primer
Large colour changes, weak-hiding colours and an unsuitable primer shade can require additional coats.
Spray technique and overspray
Distance, speed, overlap, wind and access all affect how much paint reaches the surface.
Testing and reserve quantity
Test cards, edge coating and keeping enough material for the uninterrupted final coat all need allowance.
Quantity checks
What to confirm before calculating
Measure the correct area, count all coated faces and calculate every product layer separately.
01
Painted area
Measure the surfaces that will receive paint rather than the object's floor footprint or overall room size.
02
All sides and faces
Add front, back, sides, edges, returns and separate parts where they will be coated.
03
Product coat count
Use the coat count stated on the product label or Technical Data Sheet, not a guess from another coating.
04
Separate coating layers
Calculate primer, colour coat and clearcoat separately because each product has its own coats and coverage.
05
Application allowance
Use a higher allowance for detailed shapes, outdoor spraying, texture, mesh, edges or difficult access.
06
Order enough together
Ordering enough at the start helps avoid running out during the final coat and reduces the risk of batch variation.
Step-by-step
How to plan your aerosol quantity
Measure, calculate, add an allowance and repeat the process separately for every coating product in the system.
Measure every painted surface
Measure the width and height of each flat face and record the dimensions in metres. Include edges, returns and the reverse side only where they will also be painted.
For repeated items, calculate one item and multiply by the quantity.
Add all areas together
For rectangles, multiply width by height. Add the area of every separate face or component to produce the total square metres for one coat.
Do not subtract small openings unless they are genuinely left unpainted and represent a meaningful area.
Confirm the number of coats
Use the product label or Technical Data Sheet to confirm whether one, two or more coats are required.
Primer, colour coat and clearcoat may all have different coat requirements.
Calculate the total coated area
Multiply the measured surface area by the number of coats. A 6m² project receiving two coats represents 12m² of coated area.
This coated-area figure is the basis of the aerosol calculation.
Divide by the planning coverage rate
Divide the total coated area by 1.5m² per 400ml aerosol. Always round the theoretical result up to the next complete can.
This gives the minimum planning quantity before application allowance.
Add an allowance and round up
Add an allowance for overspray, edges, texture, test passes and the complexity of the item. Fifteen per cent is a useful general starting point; complex work may need more.
Round up again to a complete aerosol.
Repeat the calculation for each product
Calculate primer, colour and clearcoat as separate products. Do not combine their coat counts into a single aerosol total.
Use the coverage and coat instructions for each exact product.
Order enough and test before the full project
Order enough material to complete the final coat without interruption, then test the spray pattern, colour and finish on a representative panel.
If the test shows extra coats or unusual loss, revise the quantity before continuing.
Measuring and examples
Useful area formulas and planning examples
Measure in metres so the answer is already in square metres. Use the calculator after adding every painted face.
Flat rectangleWidth × height. Example: 2m × 1.5m = 3m² for one face.
Door or panel, both sidesCalculate one face, multiply by two, then add the edges if they are being painted.
Several identical itemsArea of one complete item × number of items.
Frames, railings and open workMeasure the approximate coated area and select a higher allowance because edges and gaps create more overspray.
3m² × 2 coatsMinimum 4 aerosols; approximately 5 aerosols with a 15% allowance.
6m² × 2 coatsMinimum 8 aerosols; approximately 10 aerosols with a 15% allowance.
Important: The calculator uses a planning rate of 1.5m² per 400ml aerosol for one coat. Actual usage can be higher or lower, so check the exact product information and project conditions.
Useful answers
Frequently asked questions
How far will one 400ml aerosol cover?
For planning, use approximately 1.5m² for one coat from one 400ml aerosol. This is not a guaranteed yield: surface texture, shape, product, colour change, coat build and spraying technique can all alter the actual result.
How many coats should I calculate for?
Use the coat count stated on the exact product label or Technical Data Sheet. Do not assume every primer, colour coat or clearcoat requires the same number of coats.
Should primer and clearcoat be included in the same total?
No. Calculate primer, colour coat and clearcoat separately because they are different products and may have different coat counts, coverage rates and application losses.
Why do gates, railings and furniture use more paint than a flat panel?
Edges, tubes, mesh, curves, gaps and multiple spraying angles create more overspray and make it harder to transfer all the paint onto the surface. Use a higher allowance for detailed or open-work items.
What should I do if the result falls between two cans?
Always round up to a complete aerosol, then consider the application allowance. It is safer to have one can remaining than to run out partway through the final coat.
Measure carefully and order enough to finish the final coat
Use the calculator as a planning guide, round up to full cans and include an allowance for the way the project will actually be sprayed.