· Built around the Paint calculator
Photo: Malte Luk on Pexels (free licence)
The most expensive DIY mistake is the second trip to the hardware store - or the five bags of cement left hardening in the garage. Every count below is worked from the measurements, the way our paint, tiles, area, bricks, plaster, concrete, paving and roof sheets calculators do it, with the supplier figures each one rests on.
Run your own numbers
The calculator starts on the example room: 4 m x 3 m, 2.6 m high, one door, 2 m² of windows, two coats. Measure your room and type it in.
Checked against published figures
There is no SANS table for a DIY shopping list, so CalcSA checked each calculator against the maker's or supplier's own published figures:
- Concrete: 20-25 MPa is 1 : 2.5 : 2.5 at 7.5 bags of cement a cubic metre (25-30 MPa is 1 : 2 : 2 at 9 bags) - Sephaku Cement's mix table. Our concrete calculator gives 1.2 m³ x 7.5 = 9 bags for the slab below - the same.
- Roof sheets: IBR covers 686 mm a sheet and corrugated 762 mm - Clotan Steel product pages. Our roof sheets calculator gives 10 m / 0.686 = 14.58, so 15 sheets a side.
- Paint: South African enamel covers about 8 to 10 m² a litre a coat, two coats recommended - Dulux's South African product page. Our paint calculator uses the rate you type: 6.55 L at 10 m²/L, 8.19 L at 8 m²/L.
- Grout: kg a m² = 1.8 x joint x depth x (tile length + width) / (length x width) - Weber's grout data sheet. Our tiles calculator gives 0.144 kg a m², 1.73 kg for 12 m².
Not verified from a primary source: the Weber grout formula and Clotan's corrugated cover width were read from search excerpts and product pages, not the full data sheets. The brick count is geometry on a standard 222 x 106 x 73 mm brick - the Clay Brick Association's site could not be reached. Plaster dry-volume (1.27) and the 32.5 litre bag and 65 litre wheelbarrow are trade rules of thumb.
Worked example 1: paint and tile one room
- Floor: 4 m x 3 m = 12 m² - 129.17 square feet if the tile box is imported (area calculator).
- Walls: 14 m around x 2.6 m = 36.4 m², less a door and 2 m² of windows = 32.75 m² (paint calculator).
- Two coats at 10 m² a litre: 6.55 litres - buy one 5 L and two 1 L tins. On rough plaster or light over dark, plan for 8 m² a litre: 8.19 litres.
- Tiles: 12 m² / 0.36 m² a 600 x 600 tile = 33.3, so 34 - plus 10% for cuts = 38 tiles (tiles calculator). At 4 a box that is 10 boxes.
- Adhesive at 4 kg a m²: 48 kg = three 20 kg bags. Your trowel sets the real figure - check the bag.
- Grout for a 3 mm joint on 8 mm tiles: 1.73 kg - one 5 kg bag.
Photo: Kartik Das on Pexels (free licence)
Worked example 2: a garden wall and a slab
- Wall 10 m long, 2 m high, less 2 m² for a gate = 18 m² (bricks calculator).
- A standard brick with 10 mm joints covers 0.232 x 0.083 m: 51.9 bricks a m² for a half-brick wall. 18 x 51.9 = 935, plus 5% for breakage = 982 bricks. A one-brick wall doubles it.
- Plaster 20 m² at 15 mm in a 1 : 5 mix: 3 bags of cement and 0.35 m³ of plaster sand - 5.4 wheelbarrows (plaster calculator).
- Slab 4 m x 3 m x 100 mm = 1.2 m³. At 20-25 MPa that is 9 bags of cement, and 0.73 m³ each of sand and 19 mm stone - about 11 wheelbarrows of each (concrete calculator).
- Add 5% for spillage and uneven ground and it is 10 bags. Cement goes off in damp storage, so buy what the pour needs.
Worked example 3: a patio and a roof
- Patio 6 m x 4 m = 24 m². Pavers of 200 x 100 mm: 50 a m², 1 200 pavers, 1 260 with 5% extra (paving calculator).
- Bedding sand 25 mm deep: 24 x 0.025 = 0.60 m³ - about 9 wheelbarrows, on a compacted base of 100-150 mm.
- Gable roof, 10 m along the eaves, 4.5 m from eaves to ridge: 15 IBR sheets a side, 30 sheets of 4.5 m - 90 m² of roof and 10 m of ridge capping (roof sheets calculator).
- Corrugated sheets cover more width: 14 a side, 28 sheets. A slope longer than the longest sheet you can carry needs two sheets lapped 150 mm.
- Price the job before you start - every calculator above takes a unit price, and the building cost calculator gives the rand a m² for a full extension.
Before you buy
- Measure twice and write it down - every count above moves with the metres.
- Buy tiles, bricks and pavers from one batch - colour changes between batches, and a top-up order may not match.
- Structural work needs plans: walls over the height in your municipality's by-laws, roofs and slabs carrying a load are for a builder and an engineer, not a calculator.
Sources
- Sephaku Cement, concrete mix table (25-30 MPa 1:2:2 at 9 bags, 20-25 MPa 1:2.5:2.5 at 7.5 bags, 10-15 MPa 1:3.5:3.5 at 5 bags per cubic metre): sephakucement.co.za, read by CalcSA 16 October 2026.
- Clotan Steel, IBR and corrugated roof sheet product pages (686 mm and 762 mm effective cover): clotansteel.co.za. Corrugated cover from a single supplier source.
- Dulux South Africa, gloss enamel product page - about 8-10 m² a litre a coat, two coats: dulux.co.za, read 16 October 2026.
- Saint-Gobain Weber, weberjoint grout consumption formula. Read from a search excerpt; the data sheet PDF was not opened.
Calculators used in this post
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