Use our free mortar calculator to work out how much cement and sand you need for brickwork, floor tiling, wall render or paving. Select your application type, enter your dimensions and mix ratio, and get instant results in kg and 25kg bags — no sign-up required.
Mortar Calculator
Select your mortar type:
How to Use the Mortar Calculator
- Select your application type — Brickwork, Floor Tiles, Wall Render or Paving.
- Switch between Metric and Imperial if needed.
- Enter your area dimensions (length and height or width).
- Choose your mix ratio — 1:4 is the most common general-purpose mortar.
- Set a wastage percentage (10% recommended).
- Click Calculate Mortar to see cement and sand quantities in kg and 25kg bags.
Mortar Mix Ratios Explained
Mortar mix ratios describe the proportion of cement to sand by volume. The higher the sand proportion, the weaker but more workable the mix. Choosing the right ratio for the job ensures durability and avoids cracking.
| Mix Ratio | Strength | Typical Use |
|---|---|---|
| 1:3 | Strong | Pointing, coping stones, below DPC brickwork |
| 1:4 | General purpose | Most brickwork, block laying, bed joints |
| 1:5 | Standard | External render, internal backing coats |
| 1:6 | Weak / flexible | Internal render, lightweight blockwork |
Mortar Coverage Guide
Coverage varies depending on application type and the thickness of the mortar bed. Our calculator uses the following standard values:
- Brickwork: Approximately 0.033 m³ of mortar per m² of wall (standard stretcher bond, 10mm bed and perpend joints).
- Floor tiles: Based on mortar bed depth — typically 10mm for adhesive-style bed, up to 50mm for a traditional sand and cement screed bed.
- Wall render: Based on coat thickness — typically 12–15mm for a single coat scratch-and-finish system.
- Paving: Based on bed depth — typically 30–50mm for a compacted sand and cement bed under concrete or natural stone flags.
Mortar Calculator — Frequently Asked Questions
How much mortar do I need per m² of brickwork?
For standard UK stretcher bond brickwork with 10mm joints, you will need approximately 33 litres of mortar per m² of finished wall. Our calculator applies this figure automatically when you select the Brickwork option.
What is the difference between mortar and concrete?
Mortar is a mixture of cement, sand and water used to bond masonry units such as bricks and blocks, or to form a bed for tiles and paving. Concrete includes aggregate (gravel or crushed stone) in addition to cement and sand, giving it greater compressive strength for structural use. For slab and foundation calculations, use our Concrete Slab Calculator.
How many 25kg bags of cement do I need?
The calculator outputs the number of 25kg bags of both cement and sand required. These are the standard bag sizes sold in UK builders merchants. If you are buying bulk sand (loose or in a bulk bag), divide the total sand weight by 1,000 to get tonnes.
Should I add plasticiser to my mortar?
Plasticiser (or mortar plasticiser) is a liquid additive that improves workability and frost resistance. It is commonly used in external brickwork and render. When using plasticiser, reduce the water content slightly — the calculator gives dry material quantities only. Always follow the manufacturer's dosage instructions on the bottle.
