Cement Mortar Calculation for Brickwork — 1:4 and 1:6 Ratios

Introduction

One of the most common calculations a contractor or site engineer does is figuring out how much cement and sand to order for brickwork. Get it wrong and you either run short mid-pour (delays, extra transport costs) or over-order (wasted money sitting on site).

This guide walks you through cement mortar calculation for brickwork step by step. We cover 1:4 and 1:6 mix ratios, the dry volume factor, and worked examples for 1 cubic metre and a 100 sq ft wall — the two most practical reference points on any Indian construction site.

Understanding Mortar Mix Ratios

A mortar mix ratio like 1:6 means 1 part cement to 6 parts sand by volume. The total parts = 1 + 6 = 7.

Here are the common ratios used in Indian brickwork:

Mix Ratio	Cement : Sand	Strength	Typical Use
1:3	1 part : 3 parts	Very high (~10 N/sq mm)	Damp-proof courses, underground masonry
1:4	1 part : 4 parts	High (~7 N/sq mm)	External walls, load-bearing walls, parapets
1:6	1 part : 6 parts	Medium (~3 N/sq mm)	Internal walls, general above-ground work
1:8	1 part : 8 parts	Low (~1.5 N/sq mm)	Temporary structures, compound walls

For most residential construction in India, 1:6 is the standard ratio for internal brickwork and 1:4 for external or load-bearing walls.

The Dry Volume Factor — Why 1.33?

This is the concept that confuses most beginners.

When you mix dry cement and dry sand together and add water, the resulting wet mortar occupies less volume than the dry ingredients. Why? Cement particles are much finer than sand grains. During mixing, cement fills the voids between sand particles, and water further compacts everything.

The volume shrinks by approximately 25% when going from dry mix to wet mortar.

So if you need 1 cubic metre of wet mortar in place, you actually need:

Dry volume = Wet volume x 1.33

This 1.33 factor (some references use 1.30 to 1.35) accounts for the volume loss during mixing. It is a standard factor used across Indian construction practice and in CPWD analysis of rates.

Step-by-Step: Mortar Calculation for 1 Cubic Metre of Brickwork

Let us calculate materials for 1 cum of brickwork using standard bricks (190 x 90 x 90 mm) with 10 mm mortar joints.

Step 1: Find Mortar Volume

In 1 cubic metre of brickwork:

• Volume of bricks = number of bricks x volume of one brick
• Standard brick count = 500 bricks per cum (with mortar joints)
• Volume of one brick = 0.19 x 0.09 x 0.09 = 0.001539 cum
• Total brick volume = 500 x 0.001539 = 0.7695 cum
• Wet mortar volume = 1 - 0.7695 = 0.2305 cum

We will round this to 0.23 cum of wet mortar per cubic metre of brickwork.

Step 2: Apply Dry Volume Factor

Dry mortar volume = 0.23 x 1.33 = 0.3059 cum

Round to 0.306 cum of dry materials needed.

Step 3: Calculate Cement and Sand for 1:6 Ratio

Total parts = 1 + 6 = 7 parts

Cement volume: = (1/7) x 0.306 = 0.0437 cum = 0.0437 / 0.0347 = 1.26 bags (1 bag of cement = 0.0347 cum = 50 kg)

Sand volume: = (6/7) x 0.306 = 0.262 cum

Step 3 (Alternate): Calculate for 1:4 Ratio

Total parts = 1 + 4 = 5 parts

Cement volume: = (1/5) x 0.306 = 0.0612 cum = 0.0612 / 0.0347 = 1.76 bags

Sand volume: = (4/5) x 0.306 = 0.245 cum

Summary Table: Materials per Cubic Metre of Brickwork

Material	1:6 Ratio	1:4 Ratio
Cement	1.26 bags (63 kg)	1.76 bags (88 kg)
Sand	0.262 cum	0.245 cum
Bricks	500 nos.	500 nos.
Water	65-75 litres	70-80 litres

Note: Add 5% wastage for cement and 10% for sand for practical ordering.

Worked Example: 100 Sq Ft Brick Wall (9-Inch Thick)

Now let us do a real site example. You need to build a 100 sq ft wall, 9 inches (230 mm) thick, using 1:6 mortar.

Step 1: Convert Area and Find Volume

• Wall area = 100 sq ft = 9.29 sq m
• Thickness = 9 inches = 0.23 m
• Volume of brickwork = 9.29 x 0.23 = 2.137 cum

Step 2: Calculate Materials

Using our per-cum figures for 1:6 mortar:

Material	Per Cum	For 2.137 Cum	With Wastage
Cement	1.26 bags	2.69 bags	2.83 bags (3 bags)
Sand	0.262 cum	0.56 cum	0.62 cum
Bricks	500 nos.	1,069 nos.	1,122 nos. (with 5% breakage)

So for a 100 sq ft, 9-inch thick wall, order 3 bags of cement, about 0.6 cum of sand, and 1,125 bricks.

Same Wall in 4.5-Inch Thickness (Half Brick)

For a 4.5-inch (115 mm) partition wall:

• Volume = 9.29 x 0.115 = 1.068 cum
• Cement = 1.068 x 1.26 = 1.35 bags → 1.5 bags (with wastage)
• Sand = 1.068 x 0.262 = 0.28 cum → 0.31 cum
• Bricks = 1.068 x 500 = 534 → 561 nos.

Quick Reference Table: Common Wall Sizes

Here is a ready-reckoner contractors can save on their phone:

Wall Size	Thickness	Cement (1:6)	Sand	Bricks
10 x 10 ft (100 sq ft)	9 inch	3 bags	0.62 cum	1,125
10 x 10 ft (100 sq ft)	4.5 inch	1.5 bags	0.31 cum	561
10 x 10 ft (100 sq ft)	9 inch (1:4)	4 bags	0.52 cum	1,125
20 x 10 ft (200 sq ft)	9 inch	6 bags	1.24 cum	2,250
20 x 10 ft (200 sq ft)	4.5 inch	3 bags	0.62 cum	1,122

Material Cost Estimate (2026 Prices)

Here is what these materials cost in major Indian cities as of early 2026:

Material	Mumbai	Delhi	Bangalore	Pune
Cement (per bag)	Rs 380-420	Rs 360-400	Rs 370-410	Rs 370-400
Sand (per cum)	Rs 2,500-3,200	Rs 1,800-2,400	Rs 2,200-2,800	Rs 2,000-2,600
Bricks (per piece)	Rs 9-12	Rs 7-10	Rs 8-11	Rs 7-10

For our 100 sq ft, 9-inch wall (1:6 mortar):

• Cement: 3 bags x Rs 400 = Rs 1,200
• Sand: 0.62 cum x Rs 2,500 = Rs 1,550
• Bricks: 1,125 x Rs 9 = Rs 10,125
• Material total: approximately Rs 12,875

Add labour (Rs 800-1,200 per cum for brickwork) and the all-inclusive cost comes to about Rs 15,000-17,000 for 100 sq ft of 9-inch wall in a metro city.

Common Mistakes to Avoid

1. Forgetting the Dry Volume Factor

The single biggest error. If you calculate materials based on wet volume only, you will be short by 25-33%. Always multiply wet mortar volume by 1.33.

2. Using Weight Ratio Instead of Volume Ratio

1:6 means 1 part cement to 6 parts sand by volume, not by weight. Sand is heavier per unit volume than cement. Mixing by weight with the same numbers gives a much richer (and more expensive) mix than intended.

3. Not Accounting for Wastage

On real sites, mortar drops off during laying, some gets wasted during mixing, and bricks break during handling. Always add 5% extra for cement, 10% for sand, and 5% for bricks.

4. Ignoring Brick Size Variation

The calculation above uses standard modular bricks (190 x 90 x 90 mm). If your site uses country bricks or a different size, the brick count and mortar volume will change. Always measure the actual brick dimensions being used.

How the Yojo App Helps

Doing these calculations by hand every time is tedious and error-prone. The Yojo Cement Calculator lets you enter the mortar ratio, wall dimensions, and thickness — and instantly gives you cement bags, sand volume, and cost estimates.

For brick quantity, use the Brick Calculator to get exact numbers including wastage.

Use our free calculators to save time on site and reduce material ordering errors.

Summary

Cement mortar calculation for brickwork boils down to three steps:

1. Find the mortar volume — subtract brick volume from total wall volume
2. Apply 1.33 dry volume factor — to convert wet volume to dry material volume
3. Split by ratio — divide cement and sand portions based on mix ratio (1:4, 1:6, etc.)

For 1 cubic metre of brickwork in 1:6 mortar, you need 1.26 bags of cement and 0.262 cum of sand. For 1:4 mortar, it goes up to 1.76 bags and 0.245 cum of sand.

Keep these figures handy, verify with a quick calculator check, and you will never over-order or under-order materials again.