Sand and cement calculator: any ratio
The calculator needs JavaScript. The worked example, formula and figures below show exactly how it works, so you can do the sum yourself. A guide, not advice. Check your supplier's or maker's figures before ordering.
Short answer
Worked example
| You enter | Value |
|---|---|
| What are you mixing for? | Bricks |
| Number of bricks or blocks | 1,000 |
| Unit length | 215 mm |
| Unit height | 65 mm |
| Unit width | 103 mm |
| Joint | 10 mm |
| Mix | 4:1 sand to cement (1:4 cement to sand) |
| Parts sand to 1 part cement | 4 parts |
| Sand | Building (soft) sand |
| Waste allowance | 10% |
| Dry-volume factor | 1.3 × |
| Sand density | 1.5 t/m³ |
| Cement density | 1,440 kg/m³ |
| Cement bag size | 25 kg |
| Bulk bag size | 0.85 t |
Order: 5 × cement bags and 0.51 t of sand (4:1 sand to cement (1:4 cement to sand))
| Result | Value |
|---|---|
| Cement bags | 5 |
| Sand | 510.1 kg |
| Sand bulk bags | 1 |
| Mix | 4:1 sand to cement (1:4 cement to sand) |
| Cement | 122.4 kg |
| Mortar (wet volume, with waste) | 0.327 m³ |
| Dry materials | 0.425 m³ |
| Cement per 100 units | 12.2 kg |
| Sand per 100 units | 51 kg |
| Cement per m² | 7.3 kg |
| Sand per m² | 30.2 kg |
Show the working
- Per unit: ((0.215 + 0.01) × (0.065 + 0.01) − 0.215 × 0.065) × 0.103 m = 0.000297 m³
- Wet mortar: 1,000 × 0.000297 × 1.1 (10% waste) = 0.327 m³ (about 16.9 m² of wall, one skin)
- Mix: 4:1 sand to cement (1:4 cement to sand)
- Dry volume: 0.327 × 1.3 = 0.425 m³
- Cement: 0.425 ÷ (1 + 4) × 1,440 kg/m³ = 122.4 kg
- Sand: 0.425 × 4 ÷ (1 + 4) × 1.5 t/m³ = 0.51 t
- Cement bags: 122.4 kg ÷ 25 kg, rounded up = 5
- Sand bulk bags: 0.51 t ÷ 0.85 t, rounded up = 1
- Per 100 units: 12.2 kg cement and 51 kg sand
- Per m²: 122.4 kg ÷ 16.88 m² = 7.25 kg cement; 30.2 kg sand
How it works
- 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.
Our default (adjustable)
These are typical planning figures and our own allowances, not facts about your product. Change any of them in the calculator to match your bag, pack or tin.
| 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. |
Regulations and standards
- Mix ratios here are typical cement makers' mixes, not designed mortar classes (BS EN 998-2)
Our checks use the guidance for England unless a badge says otherwise. Wales, Scotland and Northern Ireland have their own rules: check the source for where you live.