Mortar & Cement Mix Calculator, South Africa
Calculate cement bags and building sand for brickwork mortar. Enter wall area or brick count with your mix ratio for the quantities to order.
Quick answer: For every 1,000 standard stock bricks (222×106×73mm) at a 1:4 mix, you need about 4 bags of 50kg cement and 0.45m³ of building sand at the default 10% wastage. Maxi bricks (290×140×90mm) take more mortar: about 6 bags and 0.75m³. Figures follow the Concrete Society of Southern Africa's 2024 mortar leaflet, as at October 2026.
Mortar Calculator
A 1:4 mix takes about 10 bags of cement and 1.25m³ of sand per m³ of mortar
For planning purposes only. Consult a registered contractor for structural brickwork specifications.
How to Use This Calculator
- Choose your input methodSwitch between Wall Area (m²) and Number of Bricks using the toggle. Both give the same result, so use whichever figure you already have.
- Enter your wall area or brick countEnter the net wall area in square metres if using Wall Area mode, or the total number of bricks to be laid if using Number of Bricks mode.
- Select brick typeChoose stock or face brick (222×106×73mm) or maxi brick (290×140×90mm) to match what you are using.
- Select wall typeChoose single skin or double skin. Double skin walls use about two and a half times the mortar of single skin for the same area, because the joint between the two skins is filled as well.
- Select mortar mix ratioUse 1:6 (Class II) for house and garden walls, the mortar SANS 10400-K names for masonry walls. Use 1:4 (Class I), this calculator's default, for highly stressed masonry or where your engineer specifies it. Use 1:3 only where specified: it is richer than Class I.
- Select wastage factorChoose 10% for standard work, 15% for complex corners and reveals that produce more cutting waste, or 20% for high builds, where mortar dries out faster and more is wasted.
- Click Calculate MortarResults show cement bags required, mortar volume, building sand in cubic metres and bulk bags, brick count, mix ratio used and a cement per 1,000 bricks reference.
Mortar Quantities for SA Brickwork: The Full Guide
Mortar is one of the most underestimated material costs in any brickwork project. Many people calculate bricks correctly but forget to budget properly for the cement and sand that hold them together. The volume of mortar required depends on the brick size, joint thickness and wall configuration. Once the materials are sorted, the Bricklaying Labour Calculator prices the labour to lay the bricks.
Mortar Quantities Per 1000 Bricks: SA Reference Table
| Brick Type | Mix Ratio | Cement (50kg bags, 10% wastage) | Building Sand | Application |
|---|---|---|---|---|
| Stock / Face (222×106×73mm) | 1:4 | 4 bags | ~0.45 m³ | Class I, the calculator's default |
| Stock / Face (222×106×73mm) | 1:3 | 5 bags | ~0.42 m³ | Richer than Class I, only where specified |
| Maxi brick (290×140×90mm) | 1:4 | ~6 bags | ~0.75 m³ | Class I, the calculator's default |
| Maxi brick (290×140×90mm) | 1:3 | 8 bags | ~0.71 m³ | Richer than Class I, only where specified |
Mortar Volume Formula
Mortar per brick (m³) = wall volume per brick − brick volume, with 10mm joints
Stock brick (222×106×73mm): 0.000323 m³ per brick
Maxi brick (290×140×90mm): 0.000546 m³ per brick
Mortar volume (m³) = (bricks laid × mortar per brick + double-skin collar joint 0.010 m³ per m² of wall face) × wastage
Cement bags = Mortar vol × 1.63 ÷ (ratio+1) ÷ 0.033
Sand (m³) = Mortar vol × 1.571 × ratio ÷ (ratio+1)
Which Mortar Mix Ratio Should You Use?
1:6 mix (Class II, 200 litres of sand per 50kg bag): The mortar SANS 10400-K names for masonry walls, including free-standing, retaining and parapet walls where the masonry units meet the standard's minimum strength. The Concrete Society of Southern Africa says Class II mortars are used for most applications, so it suits ordinary house and garden walls.
1:4 mix (Class I, 130 litres of sand per 50kg bag): For highly stressed masonry or where your engineer or drawings specify it. It is this calculator's default, so a result you have not changed is a 1:4 result: pick 1:6 for an ordinary house or garden wall. Stronger than Class II and stiffer to work.
1:3 mix (richer than Class I): Only where specified. The standard and the Society's leaflets do not name it, and a richer mix is stiffer to work and more prone to shrinkage cracking.
Why Mortar Quality Matters
Over-watering mortar is one of the most common mistakes in SA brickwork. Over-wet mortar produces staining on face bricks, weak joints and increased shrinkage cracking. Mortar of the correct consistency holds its shape when squeezed, and no water runs out of it. Mix only what you can use in 1–2 hours (our estimate). Do not add water to mortar that has started to stiffen.
Water quality matters more than most builders realise. Seawater or water with dissolved salts should never be used in mortar: the salts cause efflorescence (white staining) on face brick that is extremely difficult to remove. Use clean, potable water, and only as much as the squeeze test above allows.
Mortar Joint Finishing in SA Conditions
The finishing of mortar joints affects both appearance and waterproofing. Flush joints (scraped flat) are most common in South Africa and suit walls that will be plastered. The Plaster Calculator works out the cement and sand for the plaster. Recessed joints used decoratively on face brick should not be raked more than about 6mm (our estimate, so check your face brick supplier's guidance): deeper recesses trap water and accelerate deterioration in wet climates. Weathered joints (angled to shed water) are best for external face brick in high-rainfall areas.
Tool the joints once the mortar has stiffened enough to hold a thumbprint, usually 2 to 4 hours after laying, quicker in heat and slower in the cold. In cold weather, protect fresh brickwork from frost for at least 48 hours (both times are our estimate). Frost damage to green mortar is irreversible and the affected section must be demolished and relaid.
A Worked Example: Mortar for a Full Garage Wall
Consider a single-garage wall built with 1,500 standard stock bricks (222×106×73mm) using the default 1:4 cement:sand mix at the calculator's default 10% wastage. That works out to 6 bags of 50kg cement and approximately 0.67m³ of building sand, about two-thirds of a cubic metre. If the same wall area used maxi bricks instead, you would need around 950 bricks (maxi bricks are larger), and the mortar comes out almost the same: about 6 bags of cement and 0.72m³ of sand, because the larger brick has fewer joints but each joint is longer. A maxi brick takes more mortar than a stock brick (0.000546m³ against 0.000323m³), so a figure per 1,000 bricks cannot be carried from one brick size to another. This is why mortar quantity should always be calculated from the wall area or brick count, the brick type and the mix ratio, rather than assumed from a general rule of thumb across different brick sizes. Buying cement in round-number bag quantities rather than the exact calculated figure also builds in a small natural buffer against mixing wastage on site, which is difficult to avoid entirely even with careful batching. Sand moisture content also affects the final mix volume in practice: damp sand bulks up compared to dry sand at the same mass, so builders working from delivered sand rather than a controlled batching plant should expect some variance from the calculated figure and keep a small reserve on hand.
Frequently Asked Questions
For every 1,000 standard stock bricks (222×106×73mm) using a 1:4 cement:sand mix, you need approximately 4 bags of 50kg cement and 0.45m³ of building sand. Maxi bricks (290×140×90mm) take more mortar, because each brick is larger: approximately 6 bags of cement and 0.75m³ of building sand per 1,000 bricks. These quantities assume a standard 10mm mortar joint and the default 10% wastage; at 20% they rise to 0.49m³ (stock) and 7 bags with 0.82m³ (maxi). The Concrete Society's mortar leaflet gives 10 to 20% as typical wastage; its separate quantities leaflet allows 20 to 50% for mortar, so for rough or high-build work allow more than the 20% the options go up to.
The Concrete Society of Southern Africa gives two mortar classes for brickwork (SANS 2001-CM1). Class II, about 1:6 (200 litres of sand to a 50kg bag of cement), is the one the Society says is used for most applications and SANS 10400-K names for masonry walls. Class I, about 1:4 (130 litres per bag), is for highly stressed masonry or where an engineer specifies it. A 1:3 mix is only used where specified. The calculator defaults to 1:4, so switch to 1:6 for an ordinary wall.
Mortar for brickwork requires building sand, also called coarse sand or sharp sand. It has angular particles that produce a stronger mechanical bond between bricks. Plaster sand (fine-grained, rounded particles) is used for wall plastering, not for mortar. Using plaster sand in mortar produces a weak joint. Always specify building sand when ordering for brickwork mortar.
Measure cement and sand by volume using a consistent container (typically a builder's wheelbarrow or bucket). Mix the dry ingredients first until the colour is uniform. Add water gradually. The mix should be firm but workable. Over-wet mortar (soupy or sloppy) is weak and causes staining. Mortar that is too dry crumbles. Correctly mixed mortar holds its shape when squeezed in your fist, and no water squeezes out of it.
Initial set: usually 2 to 4 hours depending on temperature and humidity (our estimate). Most of the strength gain comes in the first week. Design strength is judged at 28 days of curing, and the Concrete Society of Southern Africa gives 7 MPa at 28 days in the laboratory for Class II mortar. In hot, dry SA conditions, mortar dries out too quickly. Keep new brickwork shaded and lightly damp for the first 3 to 7 days (our estimate). Do not lay bricks in direct midday summer sun if the mortar surface is drying faster than you can lay.
Building sand in South Africa typically costs R200–R350 per bulk bag in 2026 (our estimate, not a price survey; we take a bulk bag as 0.75m³, so check your supplier's size), varying by province and delivery distance. Gauteng and the Western Cape tend to be cheaper due to more suppliers. Free delivery usually applies above a minimum order. Confirm with your supplier. For large projects, buying by the ton directly from a sand quarry is more economical (these two points are our estimate).
For a 1:4 mix (1 cement : 4 sand) you need approximately 10 bags of cement (50kg) and 1.25m³ of sand per 1m³ of mortar before wastage. That is the Concrete Society of Southern Africa's figure for a mix with 130 litres of sand per bag (leaflet 'Mortar mixes for masonry', 2024, mortar to SANS 2001-CM1). The dry cement and damp sand take up about 1.6 times the volume of the finished mortar. The brick size and a 10mm joint work out to roughly 0.017m³ (stock) to 0.018m³ (maxi) of mortar per m² of single-skin brickwork before wastage.
A mortar plasticiser (such as Febmix or lime) improves workability without adding excess water. This is especially useful in hot conditions where mortar stiffens quickly. Use it according to the manufacturer's instructions: the UK data sheet for Feb Febmix gives about 125 to 250ml per 50kg of cement, so check the dose on the product you buy. Do not use washing-up liquid instead, common as that is on site: it weakens mortar significantly.