Calculator
Example Data Table
| Scenario | Wall (L×H×T) | Openings | Unit size | Joint | Mix | Waste | Estimated cement |
|---|---|---|---|---|---|---|---|
| Residential partition | 8 m × 3 m × 150 mm | 1.5 m² | 190×90×90 mm | 10 mm | 1:4 | 5% | ≈ 9–12 bags (50 kg) |
| Boundary wall | 20 m × 2 m × 200 mm | 0.0 m² | 190×90×90 mm | 12 mm | 1:5 | 7% | ≈ 18–25 bags (50 kg) |
| Blockwork infill | 10 m × 3 m × 200 mm | 2.2 m² | 390×190×190 mm | 10 mm | 1:6 | 5% | ≈ 10–16 bags (50 kg) |
Formula Used
- Net wall area: A = (L × H) − A_openings
- Wall volume: V_wall = A × (T / 1000)
- Nominal unit volume: V_nom = (l+j)(w+j)(h+j)
- Actual unit volume: V_act = l × w × h
- Estimated units: N ≈ V_wall / V_nom
- Wet mortar volume: V_mw = V_wall − (N × V_act)
- Waste factor: V_mw' = V_mw × (1 + waste%)
- Dry mortar volume: V_md = V_mw' × dry_factor
- Cement volume: V_c = V_md × (c / (c+s))
- Sand volume: V_s = V_md × (s / (c+s))
- Cement mass: m_c = V_c × ρ_cement
- Bags: bags = m_c / bag_weight
- Water estimate: water(L) ≈ m_c × (w/c)
How to Use This Calculator
- Select your unit system and enter wall length, height, and thickness.
- Enter total openings area for doors and windows to subtract it.
- Enter the masonry unit size (brick or block) and the joint thickness.
- Set the mortar mix ratio (cement:sand), plus waste and dry factor.
- Click Calculate to get cement bags, sand volume, and water estimate.
- Use Download CSV or Download PDF after any calculation.
Practical Notes
- For accuracy, measure actual unit dimensions and typical joint thickness on site.
- Higher waste is common for hand mixing, small batches, and hot weather.
- Workability needs change w/c ratio; avoid excessive water in structural mortar.
- Results are estimates; verify with method statements and trial panels.
Professional Article
Scope of Mortar Estimation
This calculator estimates mortar demand by modelling the wall as net masonry volume and separating solid units from joints. It suits brickwork and blockwork where mortar fills bed and perpend joints. Outputs include wet mortar, dry ingredient volume, cement mass, sand volume, and water for batching. Use it for takeoff, budgeting, or daily batching plans.
Wall Geometry and Openings
Start with wall length, height, and thickness, then subtract door and window areas to obtain net wall area. Net area multiplied by thickness gives wall volume. Even small opening changes can noticeably reduce mortar, especially for thin partitions. For long walls, measure in segments to capture steps and returns.
Unit Size and Joint Thickness
Mortar depends strongly on unit dimensions and joint thickness. The calculator uses a nominal unit volume that adds the joint to length, width, and height, and compares it with the actual unit volume. The difference across all units approximates joint space that mortar occupies.
Mortar Yield and Dry Factor
Wet mortar volume expands when converted to dry materials because sand voids and handling losses require extra bulk. A dry volume factor around 1.30–1.35 is common for site mortar. Increase it if moisture control is poor or mixing is inconsistent. If ready-mix mortar is supplied, use wet mortar volume for ordering.
Mix Ratio Selection
Choose a cement-to-sand ratio that matches the specification and exposure conditions. Leaner mixes (such as 1:6) reduce cement cost but may lower strength and durability. Richer mixes (such as 1:3 or 1:4) improve bond and early strength for demanding work. For exterior walls, follow standards, and consider lime or plasticizers only when specified by design.
Cement Bags and Bulk Density
Cement volume is converted to mass using bulk density, then divided by bag weight to estimate bags. Bulk density varies with storage and aeration, so treat it as a planning parameter. For procurement, round up to whole bags and consider delivery increments and storage limits.
Water Demand and Workability
Water is estimated from the water–cement ratio, giving a practical starting point for batching. Actual water demand changes with sand moisture, temperature, and desired workability. Add water gradually to avoid segregation and shrinkage, and follow quality checks for consistency.
Site Controls and Cost Reduction
To reduce waste, standardize joint thickness, use gauges, and keep units damp but not saturated. Track daily output and compare measured consumption with calculated targets. Separate mortar for different tasks, protect materials from rain, and adjust waste percentage as site practices improve. Log batch counts, check joint profiles, and reconcile purchases weekly to refine future estimates quickly.
FAQs
1) Does the calculator account for doors and windows?
Yes. Enter the total openings area and the tool subtracts it from gross wall area before computing wall volume and mortar. If you have many openings, sum them first to avoid underestimating reductions.
2) Which mortar mix ratio should I use?
Use the mix specified in your drawings or method statement. Common site mixes range from 1:3 to 1:6 cement:sand. Lean mixes save cement; richer mixes improve bond and early strength but cost more.
3) Why are results shown in metric units only?
To keep calculations consistent, inputs can be metric or imperial, but the outputs are converted to metric. This avoids rounding errors across mixed units and keeps the CSV and PDF exports standardized.
4) What dry volume factor should I select?
A factor of 1.30–1.35 is typical for mortar made from damp sand and site batching. Increase it when handling losses are high or sand grading is variable. If ordering ready-mix mortar, use a lower factor.
5) How accurate is the estimated unit count?
It is an approximation based on nominal unit dimensions including joints. It is useful for planning and cross-checks, but it may differ from measured counts when patterns, cuts, cavities, or reinforcement change unit spacing.
6) Can I change cement bag size and density?
Yes. Set bag weight to match your supply (for example 50 kg or 40 kg) and adjust bulk density if your storage conditions aerate the cement. The bag estimate updates automatically with these inputs.
7) Is the water estimate a strict requirement?
No. It is a starting estimate from the water–cement ratio. Adjust water based on sand moisture, temperature, and workability targets. Add water gradually and avoid overly wet mortar that can shrink or weaken joints.
Accurate estimates help reduce waste and improve daily planning.