Calculate mortar

What does this calculator do?

The mortar calculator gives you mortar volume, sack count, mixing water per sack, and a mortar-class recommendation for your wall area. It knows twelve DIN EN 771-1 stone formats, four mortar types with real datasheet densities, three application methods with consumption surcharge, and runs a wizard for the right mortar class per DIN EN 998-2. All computations run locally in the browser — no upload, no tracking, no data leaves your device.

Five differentiating features no other mortar calculator offers together: four mortar-type pathways (normal / thin-bed / trass-lime / restoration lime) instead of just normal/thin-bed; application-method toggle with +0/+20/+30 % surcharge per LZR guidance; mixing-water calculation per sack and batch from datasheet values of 0.12–0.20 L/kg; separate first-row levelling-mortar module with always-normal-mortar rule per KS-Maurerfibel §3.3; and the DIN-EN-998-2-compliant mortar-group wizard with three yes/no questions.

The calculator follows current Eurocode 6 (DIN EN 1996), which since 2010 replaces older DIN 1053-1, plus DIN 18557 for factory-dry-mix mortar production and the LZR application guidance.

Do you also need the stone count?

This tool focuses on mortar demand. For stone count, wall-width recommendation, and wall-area measurement, the masonry calculator is the sibling tool. Both use the same twelve stone formats and are compatible: first determine stone count there, then here with the same stone format derive the exact mortar demand. Workflow: three clicks in the masonry calculator, one click here, finished shopping list.

Which four mortar types does the calculator know?

Mortar type	Density (kg/L)	Water (L/kg)	Bed joint	Application
Normal mortar	1.67	0.16	10–12 mm	NF / DF / 2DF / 3DF, classical masonry
Thin-bed mortar	1.85	0.20	1–3 mm	Planblocks (sand-lime, aerated concrete, perforated clay)
Trass-lime mortar	1.75	0.17	12 mm	Natural stone, heritage, dry walls, vaults
Restoration lime mortar	1.60	0.18	12 mm	Existing buildings, damp walls, socle restoration

The first two pathways are new-build market standards. Trass-lime and restoration-lime are the two specialty pathways for the 2026-growing heritage and natural-stone market — recommended by heritage-masonry trade standards for stone and heritage restoration, formalized in DIN 18557 as factory-dry-mix mortar classes. None of the common online calculators cover these two pathways.

What does the application method change about consumption?

Mortar-manufacturer datasheet values assume classical trowel application. Real construction-site practice often differs:

Method	Surcharge	When useful
Trowel	+0 % (datasheet base)	Standard for NF/DF/2DF/3DF, experienced masons
Dipping	+20 %	Planblocks, fast work, mortar adheres to stone edges
Mortar sled	+30 %	Large walls, uniform bands, +30 % consumption accepted for time gain

Surcharge values come from the LZR application guidance (application-method consumption correction). The top user pain when ordering — sacks ran out — almost always traces here: the calculator assumes trowel application, but the wall is built with dipping or sled. The toggle corrects exactly that.

How much mixing water per sack?

Mixing water is the variable that most mortar calculators omit — but it’s decisive for construction-site logistics. From datasheet values:

Sack size	Normal	Thin-bed	Trass-lime	Restoration lime
25 kg	4.0 L	5.0 L	4.25 L	4.5 L
40 kg	6.4 L	8.0 L	6.8 L	7.2 L

For 10 × 25-kg sacks of normal mortar that’s 40 L of mixing water for the entire batch — that has to be available as clean potable water first. On construction sites without water hookup this quickly becomes a bottleneck. The calculator shows per-sack and total water directly — no datasheet research, no over- or under-mixing.

Which mortar class per DIN EN 998-2?

Three mortar classes cover ~90 % of residential applications, based on characteristic compressive strength per DIN EN 998-2:

Class	Compressive strength	Application
M 5 (MG IIa)	5 N/mm²	Interior wall, non-load-bearing partition, light cladding
M 10 (MG III)	10 N/mm²	Load-bearing exterior wall, standard residential quality
M 15 (MG III/IIIa)	15 N/mm²	Structurally critical, premium exposed brickwork, multi-storey

The wizard asks three yes/no questions — Is the wall load-bearing? Is it an exterior wall? Is it exposed brickwork? — and names the matching class with rationale. Eight combinations collapse into three recommendations. The recommendation is informational; for load-bearing walls per Eurocode 6 a structural engineer is mandatory.

Why is the first-row levelling layer the most common mistake?

The first row of stones does NOT sit on a normal 10 mm mortar joint. It sits on a 30 to 40 mm thick levelling layer of normal mortar that compensates floor-slab or strip-foundation unevenness. Three rules from the KS-Maurerfibel §3.3:

1. ALWAYS normal mortar, even with thin-bed wall above. The levelling layer needs higher water retention.
2. 30 to 40 mm thickness as standard. For very uneven substrates 50 mm — but then plan as a two-pass with reinforcement mesh.
3. Work with spirit level and water hose, not just by eye. The first row is the reference for the entire wall.

The calculator shows the volume separately: for 8 m of wall × 11.5 cm width × 30 mm thickness this yields about 28 L of normal mortar ≈ 2 × 25-kg sack. Competitors ignore this position entirely — beginners then order too little and need re-orders.

How much wastage should I plan?

Wastage arises from dry-mix residue at the sack bottom, mixing losses, small application drops, and occasional misplaced spreading.

Situation	Recommendation
Experienced mason, small surfaces	5 %
Standard DIY/pro mix, medium walls	10 % (default)
Inexperienced, many adjustments, many small walls	15–20 %

The slider covers 5–20 %. Default is 10 % — the value most masonry-supplier calculators use.

What does the tool NOT calculate?

Intentionally excluded to keep scope and liability clean:

• No structural / load-capacity design. Eurocode 6 requires a structural engineer for load-bearing walls.
• No on-site mix ratios (1:3, 1:4 sand-cement). Factory-dry-mix mortar is the 2026 standard per DIN 18557 with mandatory CE marking; on-site mixing is niche DIY only.
• No plastering-mortar calculation (DIN EN 998-1) — separate tool concept (plaster calculator).
• No live prices / cost estimates. Violates pure-client principle; prices vary regionally and by manufacturer.
• No vendor brands. Mortar types appear as generic classes, not product names — neutral and long-term stable.
• No GPS/weather correction for setting time. Out of scope.

Which construction tools are related?

Sibling for stone count: masonry calculator. For adjacent tasks: concrete calculator for foundation + floor slab, screed calculator for the layer above the floor slab, tile calculator for the bathroom finish, insulation calculator for the exterior thermal layer.

Specialty calculators for plaster mortar and grouting mortar follow in phase B after evaluating first search-query data.

What questions do users ask most often?

The frontmatter of this page contains nine FAQ entries with schema.org/FAQPage markup, sourced from top Google ‘People Also Ask’ patterns for mortar topics. Answers address the question in the first 10 words — voice-search-optimized for smart speakers and AI search assistants.