Paint Calculator South Africa: How Much Paint Do You Need
Work out exactly how many litres of paint to buy before you head to the paint shop. Enter your room size, deduct your doors and windows, choose a coverage rate and number of coats, and get an instant litres, tins and cost estimate.
Calculate My Paint ↓Paint Calculator
Enter your room dimensions and coverage details, then press Calculate to see how much paint and how many tins you need.
Paint You Need to Buy
0 litres
Room summary
Full breakdown
| Item | Value |
|---|
This total adds your chosen wastage allowance to the base litres required to cover the paintable wall area for the number of coats selected.
To work out how much paint you need, calculate your paintable wall area, multiply it by the number of coats, then divide by your paint’s coverage rate and add a wastage allowance. For a 4m x 3m room with a 2.7m ceiling, one door and one window, using a standard 10 m² per litre coverage rate, 2 coats and 10% wastage, you would need roughly 7.6 litres. Use the calculator above for an exact figure, tin count and cost based on your own room and paint.
How to Use the Paint Calculator
Five quick steps to an accurate paint quantity for your project.
- 1 Enter your room dimensions. Measure the length, width and wall height in metres. The calculator uses these to work out the full perimeter wall area of the room.
- 2 Enter your doors and windows. Each door and window is deducted from the wall area, since these are not painted.
- 3 Choose your coverage rate and coats. Pick a coverage rate based on your surface condition, or select “Custom coverage rate” to enter the exact m² per litre figure printed on your paint tin. Two coats is standard for most jobs.
- 4 Set your wastage allowance. 10% is standard and covers touch-ups and a small reserve for future repairs.
- 5 Press Calculate. Your total litres needed appears instantly, along with the paintable area, wastage added, and tins and cost if you fill in the optional cost estimate fields.
The Paint Calculation Formula
Paint quantities are based on the paintable wall area, the number of coats, your paint’s coverage rate and a wastage allowance.
Openings Deduction (m²) = (Doors × 2) + (Windows × 1.5)
Paintable Area (m²) = Wall Area − Openings Deduction
Area With Coats (m²) = Paintable Area × Number of Coats
Area With Wastage (m²) = Area With Coats × (1 + Wastage %)
Total Litres Needed = ROUND UP( Area With Wastage ÷ Coverage Rate, to 1 decimal )
Tins Needed = ROUND UP( Total Litres Needed ÷ Litres per Tin )
Total Cost = Tins Needed × Price per Tin
The wastage allowance is applied after the coats have been factored in, then the result is rounded up to the nearest tenth of a litre. Tins are rounded up to the next whole tin, since suppliers sell paint in fixed tin sizes.
Worked Examples
Real calculations using the formula above, so you can see exactly how the total is built.
Example 1: 4m x 3m room, 2.7m walls, 1 door, 1 window, 10 m²/L, 2 coats, 10% wastage
| Wall area | 2 x (4.00 + 3.00) x 2.70 = 37.80 m² |
| Openings deduction | (1 x 2) + (1 x 1.5) = 3.50 m² |
| Paintable area | 37.80 − 3.50 = 34.30 m² |
| Area with 2 coats | 34.30 x 2 = 68.60 m² |
| Area with 10% wastage | 68.60 x 1.10 = 75.46 m² |
| Total litres needed | 75.46 ÷ 10 = 7.546, rounded up to 7.6 litres |
Example 2: 5m x 4m room, 2.4m walls, 2 doors, 2 windows, 8 m²/L, 2 coats, 10% wastage
| Wall area | 2 x (5.00 + 4.00) x 2.40 = 43.20 m² |
| Openings deduction | (2 x 2) + (2 x 1.5) = 7.00 m² |
| Paintable area | 43.20 − 7.00 = 36.20 m² |
| Area with 2 coats | 36.20 x 2 = 72.40 m² |
| Area with 10% wastage | 72.40 x 1.10 = 79.64 m² |
| Total litres needed | 79.64 ÷ 8 = 9.955, rounded up to 10.0 litres |
Example 3: 6m x 5m room, 2.7m walls, 2 doors, 3 windows, 10 m²/L, 2 coats, 10% wastage, with cost estimate
| Wall area | 2 x (6.00 + 5.00) x 2.70 = 59.40 m² |
| Openings deduction | (2 x 2) + (3 x 1.5) = 8.50 m² |
| Paintable area | 59.40 − 8.50 = 50.90 m² |
| Area with 2 coats | 50.90 x 2 = 101.80 m² |
| Area with 10% wastage | 101.80 x 1.10 = 111.98 m² |
| Total litres needed | 111.98 ÷ 10 = 11.198, rounded up to 11.2 litres |
| Litres per tin | 5 |
| Tins needed | 11.2 ÷ 5 = 2.24, rounded up to 3 tins |
| Total cost | 3 x R650.00 = R1,950.00 |
Paint Calculator Guide: How Much Paint Do You Really Need
Buying the right amount of paint keeps a painting job on budget and avoids running short partway through a wall, where a batch or colour match can be hard to repeat exactly. The calculation is straightforward in principle, wall area divided by coverage rate, multiplied by the number of coats, but getting the openings deduction and coverage rate right is what stops you buying too little or paying for tins you never open.
Why coverage rate matters more than room size
Two rooms of identical size can need very different amounts of paint depending on the surface. New or bare plaster is highly absorbent and can soak up nearly double the paint of a smooth, previously painted wall in good condition. Textured or rough walls sit in between. Always check the spreading rate printed on the back of the specific tin you plan to buy, since this varies by brand and product line, and use the custom coverage option if your paint’s rate differs from the presets.
Typical paint coverage rates
| Surface Condition | Typical Coverage | Notes |
|---|---|---|
| New or bare plaster | 6-8 m² per litre | Highly porous, absorbs the first coat |
| Textured or rough walls | 8-10 m² per litre | Uneven surface reduces spread |
| Standard smooth plastered wall | 10-12 m² per litre | Most common residential surface |
| Previously painted, good condition | 10-14 m² per litre | Sealed surface gives the best coverage |
How many coats do you need
- 1 coat: Only suitable for a light touch-up on an existing colour in good condition.
- 2 coats: The standard for most interior and exterior walls, giving even colour and adequate protection.
- 3 coats: Needed when changing from a dark colour to a light colour, on new or bare plaster, or in coastal areas where paint is exposed to salt air and humidity.
Deducting doors and windows
Doors and windows are not painted with wall paint, so their area is deducted from the total wall area before working out how much paint is needed. This calculator uses a standard allowance of 2 m² per door and 1.5 m² per window, which covers typical residential door and window frame sizes. For unusually large openings, such as sliding doors or bay windows, measure the actual opening and adjust your room dimensions accordingly for a more accurate result.
Working out tins and cost
Paint is sold in fixed tin sizes, commonly 1L, 5L and 20L, so always confirm the tin size and price from the actual product you plan to buy rather than assuming a standard size. Once you know the total litres needed, divide by the litres in one tin and round up, since suppliers do not sell partial tins. Multiply the tins needed by the price per tin for a total material cost estimate, keeping in mind that primer, filler, brushes, rollers and labour are separate costs.
Methodology
This calculator applies the standard trade formula of multiplying the paintable wall area by the number of coats, adding your chosen wastage percentage, then dividing by the coverage rate of your paint and rounding up to the next tenth of a litre and the next whole tin. It does not account for surface preparation losses beyond the coverage rate you select, colour-specific opacity requirements, or costs such as primer, filler, brushes, rollers or labour.
Assumptions used in this calculator
- The room being painted is treated as a single rectangular area based on the length, width and height entered.
- Each door deducts 2 m² and each window deducts 1.5 m² from the total wall area.
- Ceilings, trim and skirting are not included and should be calculated separately.
- Litres are rounded up to the nearest tenth, and tins are rounded up to the next whole tin, since suppliers sell fixed tin sizes.
- The cost estimate uses the price per tin you enter and does not include primer, filler, brushes, rollers or labour.
Frequently Asked Questions
Using a 2.7m ceiling, one door, one window, a standard 10 m² per litre coverage rate, 2 coats and 10% wastage, a 4m x 3m room needs roughly 7.6 litres. The exact figure depends on your ceiling height, openings, coverage rate and number of coats, so use the calculator above for a precise amount.
Two coats is standard for most interior and exterior walls. Use three coats when changing from a dark colour to a light colour, when painting new or bare plaster, or in coastal areas exposed to salt air and humidity.
10 m² per litre is a reasonable default for a standard smooth plastered wall. Check the back of your specific paint tin for the manufacturer’s spreading rate, and use the custom coverage option if it differs from the presets, since coverage varies by brand and product line.
Divide the total litres needed by the litres in one tin, then round up, since suppliers sell fixed tin sizes only. Confirm the tin size with your supplier, as this varies by brand and product range.
No. This calculator covers wall area only. Ceilings are usually painted with a different product and should be calculated separately using the ceiling’s floor area as the paintable area.
This calculator deducts 2 m² for each standard door and 1.5 m² for each standard window. For unusually large openings such as sliding doors or bay windows, measure the actual opening and adjust your room dimensions for a more accurate result.
The cost estimate covers paint only, based on the price per tin you enter. It does not include primer, filler, sandpaper, brushes, rollers, masking tape or labour, all of which should be budgeted for separately.