Concrete & Mortar Calculator (South Africa)

It depends on the volume of concrete and the strength grade, not a single rule of thumb. PPC's own published mix figures put a standard 20 to 29 MPa mix for slabs, driveways and general concrete work at roughly 6,7 bags of 50kg cement per cubic metre, plus a 10% on-site ordering buffer. As a worked example, a 4m by 3m slab at 100mm thick, 1.20 m3 of concrete, needs about 9 bags. The calculator above works this out for your own dimensions and strength grade rather than a flat per-square-metre guess.

It depends much more on how you buy the sand, stone and cement than on the slab itself. Using this calculator's own reference prices, that same 4m by 3m slab, 12 m2, works out to about R163 per square metre if you buy bagged cement plus loose sand and stone collected in bulk, about R180 to R280 per square metre for a ready-mix truck at this calculator's reference delivered rate, or about R324 per square metre if you buy every material, cement, sand and stone, in retail bags. A ready-mix truck or a bulk-collected load can genuinely work out cheaper per square metre than bagged materials, even for a fairly small pour like this one, since retail bag prices carry a bigger markup than bulk or delivered concrete. The calculator above works this out for your own slab size, strength grade and buying method side by side, rather than a single flat per-square-metre figure.

A standard fence post hole, about 300mm across and 0.6m deep, a common rule of thumb of roughly a third of the post's height above ground, needs about 1 bag of cement using the foundation-strength mix PPC recommends for post holes. For 6 holes at that size, that's about 2 bags in total. The calculator above works this out for your own hole size, depth and post count, and adds sand and stone too, since post holes still need a proper concrete mix, not just neat cement.

No, they call for different strength grades. PPC's own guide puts foundations, post holes, paths and patios at a lower 10 to 15 MPa strength using a 1:4:4 mix, while driveways, slabs and general concrete work call for a stronger 20 to 29 MPa mix at 1:3:3, and heavy-duty floors or structural work need the strongest, 30 to 35 MPa at 1:2:2. A stronger mix needs noticeably more cement per cubic metre, low strength is about 5,3 bags/m3 against high strength's roughly 9,5 bags/m3 for the same volume. The calculator above suggests the right grade for what you've selected, foundation, slab or structural, but lets you override it.

Because loose, dry materials don't add up to the volume of concrete they make once mixed and compacted, roughly 1,5 cubic metres of loose cement, sand and stone yields only about 1 cubic metre of set concrete. PPC's own published guide confirms this directly, stating that producing 1 cubic metre of concrete requires 1000 litres of mix, while its own worked example for a medium-strength 1,5 cubic metre pour lists 10 bags of cement plus 1,0 cubic metre of sand plus 1,0 cubic metre of stone, over 2,3 cubic metres of loose material for 1,5 cubic metres of set concrete. A calculator that just splits your target volume by the raw ratio numbers will under-order every time. The calculator above uses PPC's own per-cubic-metre-of-finished-concrete figures instead, not a hand-derived ratio split.

Both, and it depends on the size of your job and whether you're loading it yourself. Chamberlains, Cashbuild and Builders all sell building sand and concrete stone in 40kg bags for small DIY quantities, and most yards also sell loose sand and stone by the cubic metre for you to load onto a bakkie yourself, usually with a minimum order size, Cashbuild sells from a quarter of a cubic metre upwards, though this varies by supplier. As a worked example, that 1.20 m3 slab above needs about 36 x 40kg bags of sand and 35 x 40kg bags of stone, costing about R2 942 at this calculator's reference bag prices, versus about R1 009 buying the same 1.00 m3 of sand and 1.00 m3 of stone loose at this calculator's reference bulk yard-collection rate. The calculator above shows both totals side by side with an editable minimum order size, so you can compare which actually works out cheaper for your quantity and your own supplier's pricing. Worth knowing if you're collecting it yourself, a standard 1-ton bakkie can only safely carry about half a cubic metre of sand or stone in one load, since loose sand weighs around 1.5 to 1.6 tons per cubic metre, so that half a cube is usually the practical ceiling per trip regardless of what your yard is willing to sell you.

That's a separate, on-site mixing question from what you buy, not a purchase amount. A standard South African builder's concrete wheelbarrow holds about 65 litres, the size sold by Builders, Cashbuild and most hardware stores, so once you've bought your bags or bulk load, this tells you roughly how many wheelbarrow loads of each you're combining per mix on site. As a worked example, that 1.20 m3 slab above works out to about 13.5 wheelbarrows of sand and 14.1 wheelbarrows of stone in total. No supplier sells by the wheelbarrow, so use the bag or bulk cubic metre figures above when you're actually buying.

It comes down to volume, and to what a ready-mix truck will actually deliver. For a small job, under about 0,3 cubic metres, bagged 40kg pre-mix concrete is usually the easiest, you're only carrying and mixing a handful of bags and the convenience is worth more than the small saving. For a mid-sized job, mixing your own cement, sand and stone separately is usually the cheapest option, buying dozens of pre-mix bags gets expensive fast, and a truck genuinely won't come out for most jobs this size, Instant Readymix's own published minimum delivery is 1 cubic metre, and AfriSam's own policy charges a part-load surcharge on anything under about 5 cubic metres. Once you're ordering more than roughly 1,5 to 2 cubic metres, it's worth getting a delivered quote, buying and hand-mixing that many bags becomes impractical, and a truck can work out cheaper once you count your own time, but treat the ready-mix figure as a starting point below 5 cubic metres and confirm the real price with a supplier. The calculator above shows all three costs side by side for your exact volume, billing the ready-mix option at a realistic minimum load rather than an unrealistically small delivered amount, so you're comparing real numbers rather than guessing.

Not quite. What Builders, Cashbuild and similar yards sell as "concrete mix" or "builders mix" priced per cubic metre is a dry sand-and-stone aggregate blend for bulk yard collection, you still add your own cement and mix it, the same bulk sand and stone this calculator already prices, not wet, ready-batched concrete delivered ready to pour. For that you need a dedicated ready-mix concrete supplier, PPC, AfriSam or a local independent redi-mix company, most of which have a real minimum load, commonly around 1 cubic metre, with a part-load surcharge under about 5 cubic metres, and typical trucks carrying roughly 6 to 8 cubic metres. At this calculator's reference R1 800 to R2 800 per cubic metre range, a full truckload works out to roughly R10 800 to R22 400. The calculator above bills the ready-mix option at a realistic minimum load rather than assuming a small delivered amount.

A standard South African brick, laid as a single-leaf wall with a 10mm joint, covers about 52 bricks per square metre, according to AfriSam's own published masonry reference table. A double-leaf or cavity wall uses roughly double that, about 105 bricks per square metre, since it's effectively two brick skins. As a worked example, a 6m by 1.8m garden wall, 10.8 m2, needs about 562 bricks for a single-leaf wall. The calculator above works this out for your own wall dimensions and brick or block choice.

About 5 bags of 50kg cement and 47 x 40kg bags of sand, using PPC's Class II mortar mix and 20% bricklaying wastage allowance, for 1000 bricks laid as a single-leaf wall, roughly 19.2 m2 at AfriSam's 52-bricks-per-square-metre rate, costing about R2 264 for the cement and sand at this calculator's reference prices. A double-leaf or cavity wall covers less area for the same 1000 bricks, about 9.5 m2, but needs more mortar per brick, roughly 7 bags of cement and 69 x 40kg bags of sand. The calculator above works this out for your own wall area rather than a fixed number of bricks, since real walls are rarely an exact round thousand.

PPC's own published guide for a Class II (1:6 cement to sand) mortar mix puts a single-leaf brick wall at about 0,2 bags of cement and 0,05 cubic metres of sand per square metre, and a double-leaf wall at about 0,6 bags of cement and 0,15 cubic metres of sand per square metre, plus PPC's own recommended 20% wastage allowance for the bricklaying process. As a worked example, that 10.8 m2 garden wall above needs about 3 bags of cement and 0.65 cubic metres of sand for a single-leaf brick wall. The calculator above applies the right rate for whichever brick or block you choose.

Yes, a wider block needs more mortar per square metre of wall, even though the number of blocks per square metre stays the same regardless of width, since all standard South African blocks share the same face size and only the wall thickness changes. PPC's own figures show a 90mm block needing about 0,06 bags of cement per square metre, a 140mm block about 0,09 bags, and a 190mm block about 0,11 bags, for the exact same 12,5 blocks per square metre. The calculator above adjusts the mortar quantity automatically for whichever block width you select.

South African guidance, including PPC's own published mix tables and the SANS 10400 building regulations, puts driveways, slabs and general concrete work at 20 to 29 MPa, using a 1:3:3 mix, noticeably stronger than the 10 to 15 MPa mix recommended for a foundation, post hole or garden path, but less than the 30 to 35 MPa mix used for heavy-duty floors or precast structural work. Using a foundation-strength mix under a driveway that will carry vehicle weight risks premature cracking. The calculator above defaults to the medium-strength mix when you choose a slab, but lets you pick a different grade if your project calls for it.

A common rule of thumb is about a third of the post's height above ground, so a 1,8m fence post typically needs a hole around 600mm deep. Concreting the base gives a post far more resistance to wind and leaning over time than backfilled soil alone, using the same foundation-strength mix PPC recommends for post holes. The calculator above defaults to a 300mm hole at 0.6m deep, a common size for a standard residential fence post, but both are editable for a taller or heavier post.

Yes. The brick and block coverage rates come from AfriSam's published masonry unit reference table for standard South African sizes, and every price field, cement, sand and the brick or block itself, is editable, so it works whether you're pricing clay stock bricks, concrete stock bricks, maxi bricks priced as a standard brick equivalent, or a 90, 140 or 190mm concrete block. It's brand-neutral by design, you enter your own supplier's price.