Brickwork is counted per square metre of wall, not per brick. That single shift makes estimating straightforward: measure the wall into area, multiply by the units-per-square-metre figure for your brick or block, add a waste allowance, and convert the same area into a mortar volume.
This guide derives the per-m² method from the unit size and joint, gives the standard counts for metric brick, US modular brick and concrete blocks, covers skins, openings, bonds and mortar, and finishes with a worked example with every step of the arithmetic shown.
Standard metric brick (215 × 102.5 × 65 mm) with 10 mm joints works out at ≈ 60 bricks per m² of single-skin wall, ≈ 120 for a double skin. US modular brick runs about 7 per sq ft (≈ 75/m²); a 440 × 215 mm block wall is 10 blocks per m². Add 5–10% for waste, and allow roughly 0.026 m³ of mortar per m² of single-skin brickwork. The Brick & Block Calculator runs all of it from your wall dimensions.
The Per-Square-Metre Method
Every unit in a wall occupies a rectangle: its own length and height, plus one joint in each direction. Divide one square metre by that jointed module and you have the units per m²:
units per m² = 1 ÷ [(unit length + joint) × (unit height + joint)], with all dimensions in metres. The joint is counted once per unit, which is why it is added rather than doubled.
Run it for the standard metric brick, 215 × 65 mm on face with 10 mm joints:
- Jointed module: (0.215 + 0.010) × (0.065 + 0.010) = 0.225 × 0.075 = 0.016875 m².
- Units per m²: 1 ÷ 0.016875 = 59.3.
- Call it 60 bricks per m² single skin — the number every estimate starts from.
The same three lines work for any unit anywhere, which is the point of the method. Two joint sizes matter most: 10 mm is the standard for brick and block in metric practice, and 3/8 in (about 9.5 mm) is the US norm — close enough that the counts barely move.
The Standard Counts
| Unit | Face size + joint | Typical count |
|---|---|---|
| Metric brick, single skin (102.5 mm) | 225 × 75 mm | ≈ 60 per m² |
| Metric brick, double skin (215 mm) | two leaves of the above | ≈ 120 per m² |
| US modular brick | 8 × 2.625 in jointed | ≈ 7 per sq ft (≈ 75/m²) |
| Concrete block, 440 × 215 mm | 450 × 225 mm jointed | ≈ 10 per m² |
Check the US figure with the same arithmetic: (7.625 + 0.375) × (2.25 + 0.375) = 8 × 2.625 = 21 sq in per jointed brick; 144 ÷ 21 = 6.9, hence ≈ 7 per sq ft, or about 75 per m² — a modular brick is a little smaller on face than a metric one. The block: (0.44 + 0.01) × (0.215 + 0.01) = 0.45 × 0.225 = 0.10125 m², and 1 ÷ 0.10125 = 9.9 — call it 10 blocks per m², a figure that holds for 100, 140 and 215 mm block thicknesses alike, because the face never changes.
Single Skin, Double Skin and Everything Between
A single-skin (half-brick, 102.5 mm) wall is one brick thick — garden walls, retaining edges for raised beds, the odd outbuilding. A double skin is two leaves, and it simply doubles the count: 60 becomes 120 per m². A modern cavity wall is also two leaves — an inner block leaf and an outer brick leaf — so estimate each leaf in its own material and add wall ties, roughly 2–3 per m², as a separate line.
The mortar moves with the skins too. Typical figures: about 0.026 m³ per m² for single-skin brickwork with 10 mm joints, roughly 0.05 m³ per m² for a 215 mm solid wall, and around 0.01 m³ per m² for 100 mm blockwork — less than half the brick figure, because there are far fewer joints to fill. These are planning numbers; real consumption shifts with joint finish, frog fill and how much cutting the job involves. The mortar mix ratios guide turns those volumes into cement and sand.
Openings: Measure the Net Area
Doors, windows and gates come out of the count by area. Measure every opening on the wall as built — or as accurately dimensioned on the drawing — and subtract: net area = gross wall area − openings. Guessing at openings is one of the biggest errors in brick estimating, because a typical window takes out 1–2 m², which is 60–120 bricks per opening on a double-skin wall.
Two offsets pull the other way. Openings are spanned by lintels, and the extra courses often needed above and below add area back. And every opening creates reveals and soffits that need cut bricks — which is exactly what the waste allowance is for.
Bonds: Why the Pattern Barely Changes the Count
Stretcher bond is the default for single-skin work: every brick laid long-face out, offset half a unit per course. Flemish and English bonds — alternating stretchers and headers in their different rhythms — belong to solid double-skin walls, where turned headers tie the two leaves together. Per m² of wall face, all of them present roughly 60 brick faces per leaf, so the quantity estimate hardly notices the bond you choose.
What the bond does change is cutting. Header courses, quoin returns, raking back at openings and decorative panels all produce cuts and breakages. On a plain stretcher-bond garden wall, 5% waste is comfortable; on a heavily cut job — lots of openings, tapering panels, soldier courses — allow 10%.
Worked Example: A Double-Skin Garden Wall
A garden wall 4 m long and 1.0 m high, double skin in metric brick, with one 0.9 × 0.6 m gate opening:
- Gross area: 4 × 1.0 = 4.0 m².
- Opening: 0.9 × 0.6 = 0.54 m².
- Net area: 4.0 − 0.54 = 3.46 m².
- Bricks: 3.46 × 120 ≈ 415.2 → 416 bricks (order whole, always up).
- Waste at 8% (a gate opening means cut reveals): 416 × 1.08 ≈ 449.3 → 450 bricks.
- Mortar: 3.46 m² × 0.05 m³/m² for the 215 mm wall ≈ 0.17 m³ — say 0.18 m³ with the cuts at the opening.
Enter the same wall into the Brick & Block Calculator and it returns those numbers with the waste percentage as a dial — useful for seeing how fast a heavily cut job climbs from 5% to 10%.
Common Mistakes
- Using the naked brick size. 215 × 65 without joints gives 72 per m² — a 20% over-order. The joint belongs in the module.
- Measuring one wall and multiplying by "roughly four". Rooms and gardens are rarely rectangular; measure each run.
- Guessing openings. A window guessed at "about a metre" when it is 1.2 m wide is 15% of the count on a small wall.
- Doubling the single-skin count but not the mortar. Two leaves use about twice the mortar of one.
- No waste allowance on cut-heavy work. Returns, quoins and reveals eat bricks that never appear in the net area.
- Ordering to the brick. Bricks come in packs — commonly several hundred — and pack sizes vary by maker. Round to packs and check the pack count when ordering.
Plan It With the Brick & Block Calculator
The Brick & Block Calculator takes wall dimensions and openings, applies the per-m² counts for your chosen unit, adds your waste percentage, and totals the mortar alongside — with the Mortar Calculator one click away for mixing quantities.
Open the Brick & Block CalculatorFrequently Asked Questions
How many bricks are in a square metre?
About 60 per m² for single-skin (102.5 mm) work in standard metric brick with 10 mm joints, and roughly 120 for a double skin. US modular brick runs about 7 per sq ft, or 75 per m². For any other unit, derive it: 1 ÷ [(length + joint) × (height + joint)].
How many blocks are in a square metre?
A 440 × 215 mm block with 10 mm joints: 1 ÷ (0.45 × 0.225) ≈ 9.9 — call it 10 per m². The count is the same for 140 mm and 215 mm blocks, since the face dimensions do not change; only the mortar volume does.
How much mortar do I need for 1,000 bricks?
At 60 bricks per m², 1,000 bricks is about 16.7 m² of single-skin wall; at the typical 0.026 m³ of mortar per m², that is roughly 0.4–0.45 m³. Joint finish, frog fill and cutting all move the real figure, so treat it as a planning number.
How do I allow for windows and doors?
Measure each opening and subtract its area from the gross wall area — measured, never guessed. Keep the 5–10% waste allowance for the cut bricks at reveals and heads; on heavily glazed walls the cutting, not the area, drives the order.
Does the bond pattern change how many bricks I need?
Barely — stretcher, Flemish and English bonds all present about 60 faces per m² per leaf. What changes is the cutting: header courses, quoins and returns add cuts and breakage, which is why the waste allowance matters more than the bond.
Related MyHouseLogic Guides
The brick count is half the order; the mortar is the other half.
- Mortar mix ratios — turning that 0.18 m³ into cement, sand, bags and water.
- Concrete mix ratios — the same ratio logic for the footing the wall sits on.
- How much concrete do I need — footing and foundation strip volumes for garden walls.
- All Concrete & Building guides — slabs, sub-bases, mortar and quantities.
The bottom line: count per square metre, not per brick — 60 per m² single skin, 120 double, 10 blocks. Measure the net area with openings subtracted for real, carry 5–10% waste for the cutting, and let the mortar volume ride along at roughly 0.026 m³ per m² of single skin.