Concrete & Mortar Sand Calculator
Calculate the exact amount of concrete sand or mortar sand needed for your mix — with volume, weight, and cost outputs in metric and imperial units.
Choose the job type, enter the area and thickness, and the calculator estimates the sand portion of the mix plus a rough cement bag count.
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Concrete & Mortar Sand Calculator
Calculate the exact amount of concrete sand or mortar sand needed for your mix — with volume, weight, and cost outputs in metric and imperial units.
The concrete and mortar sand calculator estimates the quantity of fine aggregate required for concrete mixes, mortar beds, stucco coats, and rendering work. It accepts slab dimensions, wall area, or mortar thickness as inputs and returns cubic meters, cubic feet, cubic yards, and weight in tonnes or pounds. Concrete sand (also called sharp sand) has a density of 1,500 kg/m³, while masonry sand (also called soft sand) has a density of 1,650 kg/m³. A standard C20 concrete mix uses sand at a 1:2 cement-to-sand ratio by volume. A standard mortar mix uses sand at a 1:3 or 1:4 cement-to-sand ratio.
Why Use a Concrete Sand Calculator?
Concrete and mortar work requires precise sand quantities — too little causes weak joints, too much causes shrinkage cracking. There are 5 critical reasons to calculate before ordering:
- Mix ratio accuracy — a 1:2:4 concrete mix requires 2 parts sand per part cement; the calculator converts that ratio into kilograms and cubic meters for bulk ordering.
- Bag count estimation — the result shows how many 25 kg or 50 kg sand bags you need, eliminating trips back to the builders' merchant.
- Waste prevention — excess sand on-site hardens and cannot be reused in a later mix without quality testing.
- Strength compliance — BS EN 206 and ASTM C94 concrete standards require sand grading within defined limits; the calculator helps confirm density selection.
- Cost planning — entering a price per tonne gives a total material cost before work begins, preventing budget overruns.
How to Calculate Concrete Sand Quantity
Multiply the slab length by the width by the sand layer depth to get volume in cubic meters. For a 5 m × 4 m concrete slab with a 100 mm (0.1 m) sand sub-base, the volume is 5 × 4 × 0.1 = 2.0 m³. At a concrete sand density of 1,500 kg/m³, the weight is 2.0 × 1,500 = 3,000 kg (3.0 tonnes). For a mortar application, calculate the mortar volume separately using the mortar bed thickness — typically 10–15 mm for brick laying.
Concrete Sand vs Mortar Sand: Which Do You Need?
Concrete sand (sharp sand) has coarse, angular grains that interlock for maximum strength in structural applications — foundations, slabs, concrete beams, and drainage layers. Masonry sand (soft sand / building sand) has fine, rounded grains that produce a workable, smooth mortar suitable for bricklaying, block work, plastering, and external rendering. Using the wrong sand type is the most common cause of weak mortar and honeycombing in concrete. The concrete sand calculator includes both density presets so you can switch between them and compare quantities.
Sand Requirements by Project Type
A standard 1 m³ of C25 concrete requires approximately 700 kg of concrete sand and 350 kg of cement. A 10 m² brick wall with 10 mm mortar joints and standard UK bricks (215 × 102.5 × 65 mm) requires approximately 0.15 m³ of mortar, which contains about 0.11 m³ (180 kg) of sand at a 1:3 mix. External rendering at 15 mm thickness over 20 m² requires approximately 0.3 m³ of sand. A 50 m² concrete floor at 150 mm thickness requires approximately 11.25 m³ of concrete, which needs about 5.25 m³ (7,875 kg) of concrete sand.
Sand types and densities
Use the table as a quick guide when choosing a material setting for your project.
| Material | kg/m³ | Common Use |
|---|---|---|
| Sand, dry | 1,600 kg/m³ | Multi-purpose sand. Used for joint filling, equestrian arena footing, and general construction. |
| Sand, wet | 1,920 kg/m³ | Unprocessed sand. Used for backfilling, leveling, and trench support. |
| Sand, packed | 1,680 kg/m³ | Coarse, angular sand. Used under pavers, flagstone, and stepping stones at 25–50 mm depth. |
| Concrete sand | 1,500 kg/m³ | Coarse, washed sand. Used for concrete mixing, drainage layers, and pipe bedding. |
| Masonry sand | 1,650 kg/m³ | Fine, screened sand. Used for mortar mix, brick laying, stucco, and finishing work. |
| Fill sand | 1,750 kg/m³ | Unprocessed sand. Used for backfilling, leveling, and trench support. |
Concrete & Mortar Sand FAQs
Answers to the most common questions about calculating sand for concrete, mortar, and rendering projects.
For a 1:3 mortar mix, you need 3 parts sand per 1 part cement. A 25 kg bag of cement requires approximately 75 kg (about 46 L) of sand. For a 1:2:4 concrete mix using a 25 kg bag of cement, you need approximately 50 kg of sand and 100 kg of aggregate.
Concrete sand (sharp sand / coarse sand) has a bulk density of approximately 1,500 kg/m³ (93.6 lb/ft³) in dry condition. Wet concrete sand weighs approximately 1,820 kg/m³. Use the dry density for ordering and the wet density if sand is stored outdoors and will be used without drying.
A sand sub-base under a concrete slab should be 50–100 mm (2–4 inches) deep for residential driveways and footpaths. Heavy-duty industrial slabs may require 150–200 mm. The sand base is compacted before concrete is poured.
No. Play sand has fine, rounded grains that do not bond well with cement paste, producing weak concrete. Concrete requires sharp sand (coarse sand) with angular particles that interlock under compression. Using play sand in structural concrete violates most national building codes.
A standard bulk bag (tonne bag / jumbo bag / FIBC) contains approximately 850 kg to 1,000 kg of dry masonry sand. At a 1:3 mortar mix, one tonne bag of sand mixed with approximately 330 kg of cement produces about 0.85 m³ of mortar.
Standard brickwork uses a 1:3 or 1:4 cement-to-sand mortar ratio. A 1:3 mix is stronger and suitable for exposed or load-bearing walls. A 1:4 mix is softer and more suitable for internal partition walls and traditional lime-mortar compatibility.
A 15 mm coat of external render over 10 m² requires approximately 150 litres (0.15 m³) of mortar. At a 1:4 render mix, that is approximately 120 litres of sand, equating to about 5 bags of 25 kg building sand.