How many cement blocks are needed for 1 square metre of wall in Sri Lanka?

About 12 standard SLS cement blocks (400 × 200 mm face) per square metre of single-leaf wall, using a 10 mm mortar joint. The exact figure is 1 ÷ [(0.41 m)(0.21 m)] = 11.6 blocks/m² before wastage, so allow roughly 12–13 with a 5% cutting and breakage margin.

How many bricks are in a 10 foot by 10 foot wall?

A 10 ft × 10 ft wall is 100 ft² ≈ 9.29 m². At about 60 SLS bricks per m² for a half-brick (single-leaf) wall, that is roughly 557 bricks before wastage, or about 585 bricks with a 5% allowance. A double-leaf (full-brick) wall needs double that.

How many bags of cement do I need for a block wall?

It depends on the mortar volume, not the wall area alone. For a typical 30 m² single-leaf 200 mm block wall at a 1:5 mix, the joints hold about 0.43 m³ of mortar, which works out to roughly 3 bags of 50 kg cement. Richer mixes (1:3, 1:4) need more; leaner mixes (1:6) need fewer.

What is the standard cement block size in Sri Lanka?

Under SLS 855 the standard face size is 400 × 200 mm, with nominal thicknesses of 100 mm (4″), 150 mm (6″) and 200 mm (8″). The 200 mm block is common for boundary and load-bearing walls; the 100 mm block is used for partitions. This calculator ships all three as presets.

How much sand (in cubes) is needed to build a brick wall?

Sand tracks the mortar volume. For a 12.5 m² half-brick wall at 1:5, you need about 0.25 m³ of sand — roughly 0.09 of a cube (one cube = 100 ft³ = 2.832 m³). Sand is sold by the cube in Sri Lanka, so small walls often need only a fraction of a cube; the tool shows both m³ and cubes.

Does the calculator include mortar for a double-leaf wall?

Yes. Choose "Double leaf" and the tool sets the wall thickness to two units plus a joint, doubles the unit count per m², and recomputes the mortar volume from the larger wall volume. Single leaf is the default because most boundary and partition walls in Sri Lanka are one unit wide.

Why does my hardware shop's estimate differ slightly?

Small differences come from unit size, joint thickness, wastage percentage and the dry-volume factor. Bricks especially vary by kiln, so measure a few and use the Custom size option. This tool rounds units and cement bags up (you cannot buy a fraction of a bag) and reports sand to two decimals of a cube.

When were these methods and constants last verified?

The unit sizes, the 1.30 dry-volume factor, the 0.0347 m³ cement-bag volume and the 2.832 m³ cube were last cross-checked against SLS, CIDA and cement-supplier references on 2026-07-11. The two worked examples on this page were computed by hand and reconcile with the tool to the unit.

Sri Lanka · Construction

Sri Lanka Brick & Block Wall Material Calculator

Enter a wall's length, height and unit size and get the exact number of cement blocks or bricks, 50 kg cement bags, and cubes of sand it needs — with your mortar mix and wastage built in. No signup, sources cited below.

By Induwara Ashinsana— Executive Director, Ryzera TechnologiesUpdated Jul 11, 2026

Wall material estimatebricks · blocks · cement · sand

SLS · CIDA method

Quick start

Wall length

Wall height

Doors & windows to deduct

Total area of openings. Leave at 0 for a solid wall.

Block / brick size

SLS 855 face size, 200 mm (8″) thick — common boundary wall block

Wall thickness

One skin of units — the usual boundary / partition wall.

Mortar mix

Typical block & brick walls

Joint (mm)

Wastage (%)

Add prices for a cost estimate (optional)

Price per block (Rs)

Price per cement bag (Rs)

Price per sand cube (Rs)

Blocks

366

Wastage included, rounded up

Cement (50 kg bags)

1:5 (common) mortar

Sand (cubes)

0.17

0.48 m³ · ~774 kg

blocks/m²

11.6

Net face: 30 m²

Net wall face area	30 m² (322.92 ft²)
Finished wall thickness	200 mm
Gross wall volume	6 m³
Dry mortar volume	0.58 m³
Cement volume	0.1 m³
Sand volume	0.48 m³ (0.17 cube)

Shopping list

Wall material list — induwara.lk
Wall: 30 m² face, single leaf
366 blocks (Cement block — 400 × 200 × 200 mm)
3 × 50 kg cement bags (1:5 (common))
Sand: 0.17 cube (0.48 m³)

Cement quantity verified two ways — by 50 kg bag volume (0.0347 m³) and by cement mass (1440 kg/m³). Both agree.

Unit sizes follow SLS 855 (cement blocks) and SLS 39 (clay bricks). Mortar quantities use the volumetric method with CIDA's 1.30 dry-volume factor; one 50 kg cement bag = 0.0347 m³, one cube of sand = 2.832 m³.

How it works

This calculator turns a wall's geometry into a material list using the standard volumetric mortar method — the same approach behind CIDA's rate analysis and IS 2212 for brickwork. Everything is computed in metres internally (1 ft = 0.3048 m).

Net face area. Wall length × height, minus the area of any doors or windows: A = L × H − openings.
Wall thickness. One unit width for a single leaf, or two widths plus a joint for a double leaf.
Units per m². Using the joint-inclusive footprint of the unit face: n/m² = 1 / [(l + j)(h + j)], where l and h are the exposed face dimensions and j is the mortar joint. A double-leaf wall doubles this figure.
Unit count. N = ceil(A × n/m² × (1 + wastage)). Units are always rounded up.
Mortar volume. Wall volume minus the solid volume of the masonry units gives the wet mortar volume. The pre-wastage unit count is used here so mortar and units are never double-counted.
Dry volume and split.Wet mortar is multiplied by CIDA's 1.30 dry-volume (bulking) factor and the wastage allowance, then split by the mix ratio 1:m — cement = dry ÷ (1 + m), sand = m × cement.
Cement bags and sand. Cement volume ÷ 0.0347 m³ per 50 kg bag, rounded up. Sand volume ÷ 2.832 m³ gives cubes; × 1600 kg/m³ gives an approximate mass.

Unit sizes come from the Sri Lanka Standards Institution: SLS 855 sets the 400 × 200 mm cement-block face with 100/150/200 mm thicknesses, and SLS 39 gives the 215 × 102.5 × 65 mm reference clay brick. Because local bricks vary by kiln, the tool also offers the common 8″ × 4″ × 3″ brick and a custom size. The cement-bag volume is cross-checked two ways — by the 0.0347 m³ bag volume and by cement mass (1440 kg/m³ × a 50 kg bag) — and both agree, which is the “verified two ways” note shown under the results.

Worked examples

200 mm block boundary wall

10 m × 3 m · single leaf · 1:5 · 5% wastage

Face area: 10 × 3 = 30 m² (no openings)
Blocks/m²: 1 ÷ (0.41 × 0.21) = 11.61
Blocks: ceil(30 × 11.61 × 1.05) = 366
Wall volume: 30 × 0.20 = 6.00 m³
Mortar (wet): 6.00 − 5.575 = 0.425 m³
Dry mortar: 0.425 × 1.30 × 1.05 = 0.580 m³
Cement: 0.580 ÷ 6 = 0.097 m³ → ceil(0.097 ÷ 0.0347) = 3 bags
Sand: 5 × 0.097 = 0.484 m³ = 0.17 cube (~773 kg)
Result: 366 blocks · 3 cement bags · 0.17 cube sand

Half-brick internal wall

5 m × 2.5 m · SLS brick · single leaf · 1:5 · 5%

Face area: 5 × 2.5 = 12.5 m²
Bricks/m²: 1 ÷ (0.225 × 0.075) = 59.26
Bricks: ceil(12.5 × 59.26 × 1.05) = 778
Wall volume: 12.5 × 0.1025 = 1.281 m³
Mortar (wet): 1.281 − 1.061 = 0.220 m³
Dry mortar: 0.220 × 1.30 × 1.05 = 0.301 m³
Cement: 0.301 ÷ 6 = 0.050 m³ → ceil(0.050 ÷ 0.0347) = 2 bags
Sand: 5 × 0.050 = 0.251 m³ = 0.09 cube (~401 kg)
Result: 778 bricks · 2 cement bags · 0.09 cube sand

Edge case — wall smaller than its openings

4 m × 3 m wall · 15 m² of openings

Face area: 4 × 3 = 12 m²
Openings to deduct: 15 m²
Net area: 12 − 15 = −3 → clamped to 0
The tool shows a clear error instead of a negative or NaN result
Fix: reduce the openings, or check the units (m² vs ft²)

Frequently asked questions

Sources & references

Constants used: one 50 kg cement bag = 0.0347 m³ (Portland cement ≈ 1440 kg/m³); dry-volume factor = 1.30; sand bulk density ≈ 1600 kg/m³; one cube = 100 ft³ = 2.832 m³. Last cross-checked on 2026-07-11. This tool estimates straight, uniform-thickness walls only — it does not cover plaster, columns, tie beams or reinforcement.

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