Block and brick calculator — GCC blocks, bricks and mortar
A 5×3 m wall in 400×200 blocks takes 192 blocks and 19 bags of mortar at 10% waste. Enter your wall below for GCC concrete blocks or standard bricks, with the mortar counted for you — free, no signup.
Your quantities
How the blocks, bricks and mortar are worked out
Blocks: each laid block covers its face plus a 10 mm joint — 0.41 × 0.21 m — so a square metre of wall takes about 11.6 blocks, not the 12.5 you get by ignoring the joints. Mortar is the wall's volume minus the blocks' volume: roughly 14 litres per m² for a 200 mm block wall.
Bricks: the metric standard lays 59 bricks per m² and the US modular 6.85 per square foot, with waste added before rounding up. Mortar bags follow the brick count — one 25 kg bag per 35 metric bricks, one 70 lb bag per 30 US modular bricks.
Running these jobs? Masonry & Plaster
How to use the block and brick calculator
- Choose the wall type — GCC concrete blocks, or bricks.
- For blocks, pick the block size: 400×200×200 for structural walls, 400×200×100 for partitions.
- Type the wall length and height, then set the waste — 10% covers cuts and breakage.
- Read the count and the mortar: blocks or bricks to order, mortar volume and 25 kg bags.
How many blocks and bags of mortar for a 5×3 m wall?
The wall is 15 m². Each laid block covers 0.41 × 0.21 m including its 10 mm joint — 11.61 blocks per m² — so the wall takes 175 blocks before waste and 192 with 10% added.
Mortar is the wall’s volume minus the blocks in it: about 0.0142 m³ per m², or 0.21 m³ for this wall — 19 bags of 25 kg mortar at the standard 0.0125 m³ yield, waste included.
The same wall in metric bricks (215 × 65 mm) takes 974 bricks and 28 bags of mortar at the same 10% waste.
Block and brick rates the calculator uses
GCC concrete blocks — laid with a 10 mm joint
| Block size | Blocks per m² | Mortar per m² |
|---|---|---|
| 400 × 200 × 200 mm | 11.61 | 0.0142 m³ |
| 400 × 200 × 100 mm | 11.61 | 0.0071 m³ |
Brick rates and mortar bags
| Standard | Rate | Mortar bag basis |
|---|---|---|
| Metric brick 215 × 65 mm | 59 bricks per m² | 1 × 25 kg bag per 35 bricks |
| US modular brick | 6.85 bricks per sq ft | 1 × 70 lb bag per 30 bricks |
Wall-building notes from the trade
- Finishing a block wall: a two-coat plaster directly over blockwork is about 12 mm in total, and one 36 kg (80 lb) bag of basecoat covers roughly 1.9–2.2 m² at that thickness — typical bag yields; check the bag you buy.
- Dry, high-suction bricks pull water out of fresh mortar too fast and weaken the bond. Clay bricks are often pre-wetted before laying; concrete blocks are laid dry.
- Hold the 10 mm joint the calculator assumes. Fat joints eat mortar and drift the count; thin joints starve the bond.
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How many concrete blocks are in 1 m² of wall?+
About 11.6 blocks for 400×200 blocks laid with a 10 mm joint. The joint is real wall, so the honest count is lower than the 12.5 you get from the block’s face alone — a 15 m² wall at 10% waste takes 192 blocks.
How much mortar does a block wall need?+
For a 200 mm block wall, about 0.014 m³ of mortar per m² — the wall’s volume minus the blocks in it. A 15 m² wall needs roughly 0.21 m³, which is 19 bags of 25 kg mortar at a standard yield.
How many bricks do I need per square metre?+
59 bricks per m² at the metric standard (215×65 mm brick with joints), or 6.85 per square foot for US modular brick. Waste is added before the count is rounded up — a 15 m² metric wall at 10% waste takes 974 bricks.
How many mortar bags do I need per 1,000 bricks?+
About 29 bags of 25 kg at the metric rate — the calculator counts one bag per 35 bricks, so 1,000 bricks take 1,000 ÷ 35, rounded up. The 974-brick wall above takes 28 bags.
What sizes are GCC concrete blocks?+
400 × 200 × 200 mm is the standard structural block and 400 × 200 × 100 mm the partition block. Both lay at 11.61 blocks per m² with a 10 mm joint; the 100 mm wall uses about half the mortar.
How much mortar does a 100 mm block wall use?+
About half of a 200 mm wall — roughly 0.0071 m³ per m² against 0.0142 — because the wall holds half the volume. A 10 m² partition at 5% waste takes 122 blocks and 6 bags of mortar.
What size is a metric brick?+
215 mm long × 102.5 mm wide × 65 mm high — the long-standing format sold across the Gulf and Europe. With a 10 mm joint its laid face is 225 × 75 mm, which is where the 59 bricks per m² rate comes from.
How thick is a standard mortar joint?+
10 mm (⅜ inch). It balances the bricks’ dimensional tolerance against mortar strength — and it is the joint both rates on this page assume, for blocks and for bricks.
Why add a waste factor to a wall?+
For breakage in transit and cuts at ends, corners and openings. Contractors add 10–15%; this calculator opens at 10% and adds the waste before rounding the count up, for blocks and mortar alike.
What is a wythe of brickwork?+
One continuous vertical skin of wall, one unit thick. A double-wythe wall is two skins — and takes twice the bricks and twice the mortar of the single-wythe counts this calculator gives.
Should bricks be wetted before laying?+
Clay bricks with high suction, yes — a dry, thirsty brick pulls water from the fresh mortar too fast and the bond fails weak. Concrete blocks are the opposite practice: they are laid dry.
What does this calculator not include?+
No prices and no labour — quantities only, for one skin of wall. Openings are not deducted, so measure walls net of big door and window openings if you want a tighter count. The quantities do not carry into InstaJack automatically yet.