How we calculate: brickwork
Every formula and default figure our brickwork calculators use. Each figure can be changed in its calculator to match your product. See how we calculate for the method behind all of them.
Brick and block calculator
Open the brick and block calculator
- Per m² = 1 ÷ ((face length + joint) × (face height + joint)), in metres
- Count = net wall area × per m² × skins × (1 + waste), rounded up
Two skins doubles the count (for example a one-brick wall or a cavity wall's two leaves).
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| Face length: Brick | 215 mm | Common UK size Not yet checked against the source | From your product UK standard brick (work size). |
| Face height: Brick | 65 mm | Common UK size Not yet checked against the source | From your product UK standard brick (work size). |
| Face length: Block | 440 mm | Common UK size Not yet checked against the source | From your product UK standard block face. |
| Face height: Block | 215 mm | Common UK size Not yet checked against the source | From your product UK standard block face. |
| Joint | 10 mm | Common UK size Not yet checked against the source | From your product Standard UK mortar joint. |
| Waste allowance | 5 % | Our assumption Not yet checked against the source | Our choice: change it to suit your job Breakages and cuts. |
Sand and cement calculator
Open the sand and cement calculator
- Bricks or blocks: mortar per unit = ((L + j)(H + j) − L·H) × W; wet = count × per unit × (1 + waste)
- Area: wet = area × thickness × (1 + waste); volume: wet = your volume × (1 + waste)
- Dry volume = wet × dry-volume factor (dry materials shrink when mixed)
- For r parts sand to 1 part cement ("r:1 sand to cement", the same as "1:r cement to sand"): cement (kg) = dry ÷ (1 + r) × cement density; sand (t) = dry × r ÷ (1 + r) × sand density
- Cement bags = cement ÷ bag size, rounded up
"4:1 sand to cement" and "1:4 cement to sand" are the same mix: four parts sand to one part cement.
Ratios are typical mixes quoted by cement makers, not designed mortar classes. For structural work follow the engineer's or maker's specification.
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| Unit length: Bricks | 215 mm | Common UK size Not yet checked against the source | From your product UK standard brick (work size). |
| Unit height: Bricks | 65 mm | Common UK size Not yet checked against the source | From your product UK standard brick (work size). |
| Unit width: Bricks | 102.5 mm | Common UK size Not yet checked against the source | From your product UK standard brick (work size). |
| Unit length: Blocks | 440 mm | Common UK size Not yet checked against the source | From your product UK standard block face. |
| Unit height: Blocks | 215 mm | Common UK size Not yet checked against the source | From your product UK standard block face. |
| Unit width: Blocks | Enter from the bag, pack or tin | Common UK size Not yet checked against the source | From your product brief v2 B1: block thickness (wall width) for block mortar. Not stated in the brief; from the block. |
| Joint | 10 mm | Common UK size Not yet checked against the source | From your product Standard UK mortar joint. |
| Parts sand to 1 part cement: Our default mix (see the assumptions) | 5 parts sand to 1 cement | Our assumption Not yet checked against the source | Our choice: change it to suit your job Check your maker's or builder's spec; the right ratio depends on the job. |
| Sand density: Building (soft) sand | 1.5 t/m3 Sources range 1.4–1.6 t/m3 | Typical value Not yet checked against the source | aggregatecalculator.co.uk aggregate density table (checked 19 October 2026) |
| Sand density: Sharp sand | 1.6 t/m3 Sources range 1.6–1.7 t/m3 | Typical value Not yet checked against the source | aggregatecalculator.co.uk aggregate density table (checked 19 October 2026) Damp sand bulks; order by weight. |
| Waste allowance | 10 % | Our assumption Not yet checked against the source | Our choice: change it to suit your job Droppings and mixing loss. |
| Dry-volume factor | 1.3 × | Our assumption Not yet checked against the source | Our choice: change it to suit your job Dry materials shrink when mixed with water. Researcher to check against cement makers' guidance. |
| Cement density | 1440 kg/m3 | Our assumption Not yet checked against the source | Our choice: change it to suit your job Typical planning figure with no source yet. Researcher to source it and reclassify as typical. |
| Cement bag size | 25 kg | Common UK size Not yet checked against the source | From your product Common UK cement bag. |
| Bulk bag size | 0.85 t | Common UK size Not yet checked against the source | builder.tools bulk bag figure (checked 19 October 2026) Varies by merchant; check yours. |
Repointing calculator
Open the repointing calculator
- Joint share of the face = ((L + j)(H + j) − L·H) ÷ ((L + j)(H + j))
- Wet mortar (m³) = area × joint share × depth raked out × (1 + waste); dry = wet × dry-volume factor
- Binder (kg) = dry ÷ (1 + r) × binder density; sand (kg) = dry × r ÷ (1 + r) × sand density × 1,000
- Joint length (m) = area × (1 ÷ (L + j) + 1 ÷ (H + j))
Raking out and cutting mortar makes silica dust: see the silica exposure calculator.
Lime mixes are labelled for older solid walls; ask a conservation specialist for listed buildings.
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| Brick or slab length: Brickwork | 215 mm | Common UK size Not yet checked against the source | From your product UK standard brick (work size). |
| Brick height or slab width: Brickwork | 65 mm | Common UK size Not yet checked against the source | From your product UK standard brick (work size). |
| Brick or slab length: Patio joints | 600 mm | Common UK size Not yet checked against the source | From your product brief v2 L1 (PA1: 600 × 600 slab). Slabs vary; check the product. |
| Brick height or slab width: Patio joints | 600 mm | Common UK size Not yet checked against the source | From your product brief v2 L1 (PA1: 600 × 600 slab). Slabs vary; check the product. |
| Joint width | 10 mm | Common UK size Not yet checked against the source | From your product Standard UK mortar joint. |
| Parts sand to 1 part binder: Cement | 5 parts sand to 1 cement | Our assumption Not yet checked against the source | Our choice: change it to suit your job Check your maker's or builder's spec; the right ratio depends on the job. |
| Binder density: Cement | 1440 kg/m3 | Our assumption Not yet checked against the source | Our choice: change it to suit your job Typical planning figure with no source yet. Researcher to source it and reclassify as typical. |
| Binder bag size: Cement | 25 kg | Common UK size Not yet checked against the source | From your product Common UK cement bag. |
| Parts sand to 1 part binder: NHL 3.5 lime | Enter from the bag, pack or tin | Our assumption Not yet checked against the source | Our choice: change it to suit your job brief v2 B3: lime ratios from SPAB / Historic England guidance (Researcher). |
| Binder density: NHL 3.5 lime | Enter from the bag, pack or tin | Typical value Not yet checked against the source | From your product brief v2 B3: NHL lime bulk density. Researcher to source (lime maker's data). |
| Binder bag size: NHL 3.5 lime | Enter from the bag, pack or tin | Common UK size Not yet checked against the source | From your product brief v2 B3: NHL bag size, from the bag. |
| Parts sand to 1 part binder: NHL 5 lime | Enter from the bag, pack or tin | Our assumption Not yet checked against the source | Our choice: change it to suit your job brief v2 B3: lime ratios from SPAB / Historic England guidance (Researcher). |
| Waste allowance | 10 % | Our assumption Not yet checked against the source | Our choice: change it to suit your job Droppings and mixing loss. |
| Dry-volume factor | 1.3 × | Our assumption Not yet checked against the source | Our choice: change it to suit your job Dry materials shrink when mixed with water. Researcher to check against cement makers' guidance. |
| Sand density | 1.5 t/m3 Sources range 1.4–1.6 t/m3 | Typical value Not yet checked against the source | aggregatecalculator.co.uk aggregate density table (checked 19 October 2026) |
Wall tie calculator
- General ties = net wall area ÷ (spacing along × spacing up), rounded up
- Openings: each side of each opening gets ties up its height at the closer spacing (within 225 mm of the reveal): 2 × (opening height ÷ spacing, rounded up)
- Movement joints: the same, both sides of each joint
- Total = general + openings + movement joints
Spacings are Approved Document A figures for England (Researcher to cite the paragraph and table); also check the tie maker's data (BS EN 845-1).
The tie type and length depend on the cavity width: choose from the tie maker's table.
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| Tie spacing along the wall | 900 mm | Regulation or HSE figure Approved Document A (Researcher to cite paragraph and table) Not yet checked against the source | Source to be added by the Researcher brief v2 B2 (900 × 450 general spacing). Also BS EN 845-1 / tie maker. |
| Tie spacing up the wall | 450 mm | Regulation or HSE figure Approved Document A (Researcher to cite paragraph and table) Not yet checked against the source | Source to be added by the Researcher brief v2 B2 (900 × 450 general spacing). |
| Tie spacing up the sides of openings and movement joints | 300 mm | Regulation or HSE figure Approved Document A (Researcher to cite paragraph and table) Not yet checked against the source | Source to be added by the Researcher brief v2 B2 (300 mm vertical at openings and movement joints). |
Lintel length calculator
Open the lintel length calculator
- Minimum length = clear opening + 2 × minimum end bearing
- Length to order = the minimum length rounded up to the next stock length (a whole number of steps)
This gives the length only. Choose the lintel type from the maker's load tables or an engineer's specification: the load it carries is out of scope here.
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| Minimum end bearing | To be confirmed from the source | Regulation or HSE figure Lintel maker's minimum end bearing (Researcher to cite) Not yet checked against the source | Source to be added by the Researcher brief v2 B4: maker's minimum end bearing (null; typically quoted as 150 mm). User enters it from the maker's data. |
| Stock lengths go up in steps of | 150 mm | Common UK size Not yet checked against the source | From your product brief v2 B4 LN1 (150 mm stock increments). Check the maker's range (e.g. Catnic, IG, Naylor). |