the symbol ofStrengthFind my product →Enter your wall area and AAC block size — we'll work out the thin-bed mortar you need, the number of blocks, and how many bags to buy at the joint thickness you're using.
Common Indian AAC sizes (Length × Height × Thickness). Wall thickness follows the block — thicker blocks use more mortar per m².
▼Thin-bed jointing mortar is laid at 2–3 mm — far thinner than a 12 mm sand-cement bed. That's the whole point of AAC.
Supplied in one standard pack.
Extra for spillage, mixing loss & uneven courses.
Consumption is calculated from block geometry — bed and perpend joints at your chosen thickness — at roughly 25–30 kg of mortar per m³ of masonry for a 3 mm joint. A 40 kg bag of Block Jointing Mortar covers about 1.3–1.5 m³ of AAC blockwork. Actual usage varies with block flatness, workmanship and site conditions; always confirm against the product datasheet.
This calculator works out how much SUMO Block Jointing Mortar (AAC block adhesive) your wall needs — in kilograms and 40 kg bags — from the actual geometry of the blockwork: block size, wall area and the thin-bed joint thickness you lay.
Unlike rule-of-thumb estimates, it computes the real mortar volume in the bed and perpend joints, so a 100 mm partition and a 230 mm external wall get different — correct — answers.
Choose your units (feet or metres) and enter the wall length and height — or the total wall area if you already know it.
Pick the AAC block size. Indian-standard sizes from 600 × 200 × 75 mm to 600 × 240 × 200 mm are built in, or enter a custom size.
Set the joint thickness. Thin-bed jointing mortar is laid at 2–3 mm — that is the whole point of BJM versus 10–12 mm site-mix mortar.
Deduct door and window openings, and keep ~5% wastage.
Read off kilograms, 40 kg bags to buy, and blocks needed for the same wall.
Rule of thumb from the same maths: about 25–30 kg of mortar per m³ of AAC masonry at a 3 mm joint — one 40 kg bag covers roughly 1.3–1.5 m³ of blockwork.
| Block thickness | Consumption | Coverage per 40 kg bag |
|---|---|---|
| 75 mm | ≈ 2.8 kg/m² | ≈ 14.3 m² · 154 sq.ft |
| 100 mm | ≈ 3.7 kg/m² | ≈ 10.8 m² · 110–120 sq.ft |
| 150 mm | ≈ 5.6 kg/m² | ≈ 7.2 m² · 77 sq.ft |
| 200 mm | ≈ 7.4 kg/m² | ≈ 5.4 m² · 58 sq.ft |
| 230 mm | ≈ 8.6 kg/m² | ≈ 4.7 m² · 50 sq.ft |
Joint thickness is the biggest lever: on a 100 mm wall the same bag covers ≈ 16 m² at 2 mm but only ≈ 6.5 m² at 5 mm. Keep joints at 2–3 mm.
Level the first course on a conventional cement-sand bed and check it twice — every thin-bed course above inherits its accuracy.
Mix with the water ratio printed on the bag, mechanically, to a smooth lump-free paste.
Spread along the course and comb with a notched trowel to an even 2–3 mm bed — bed joint and perpends both.
Place each block within the open time and tap level with a rubber mallet; thin joints leave no room to "adjust with mortar".
Brush dust off block faces before spreading — AAC dust is the most common cause of weak thin-bed joints.
When a site burns through more bags than the calculator predicted, the cause is almost always one of these:
An unlevel first course — every course above needs extra mortar to chase level, and joints creep from 3 mm to 5 mm (nearly double the consumption).
Chipped or broken block edges being packed with mortar instead of the block being cut square.
Mortar mixed too stiff — it will not comb thin, so it gets laid thick.
Using thin-bed mortar to fill chases and gaps around frames — budget conventional mortar for those jobs separately.
500 sq.ft = 46.45 m² of wall face.
Consumption at 3 mm on 100 mm blocks ≈ 3.7 kg/m² → 46.45 × 3.7 ≈ 173 kg.
173 ÷ 40 = 4.3 → round up to whole bags.
The same wall needs ≈ 380 blocks (8.2 blocks per m² face).
On standard 600 × 200 × 100 mm AAC blocks at a 3 mm joint, one 40 kg bag lays roughly 85–90 blocks (about 10.8 m² / 110–120 sq.ft of wall). Thicker blocks use more mortar per block: on 200 mm blocks a bag covers about 5.4 m².
AAC blocks are dimensionally accurate, so they can be laid on a 2–3 mm adhesive bed instead of a 10–12 mm site-mix bed. That means far less material, faster laying, no curing of joints, water-resistant polymer-modified joints, and thinner thermal bridges through the wall.
2–3 mm. The calculator lets you model other joints, but going to 5 mm nearly doubles consumption versus 3 mm — if your blocks need 5 mm joints to level up, the substrate or block quality is the problem to fix.
Use the mixing ratio printed on the bag and in the product datasheet — downloadable from the Block Jointing Mortar product page. Mix to a smooth, lump-free paste and use within the pot life stated there.
Standard practice is to level the first course on a conventional cement-sand mortar bed so it sits perfectly level, then lay every subsequent course with 2–3 mm thin-bed jointing mortar. The calculator estimates the thin-bed quantity.