Inputs
Add wall rectangles. Deduct openings separately. Toggle “Both Sides” for two-side plastering.
| # | Length m | Height m | Qty | Area (auto) m² |
|---|
m²
Sum of doors/windows to subtract.
mm
%
Converts wet to dry (adds voids/bulking).
:
kg/m³
kg/m³
w/c
kg
currency
currency
Results
Total net area
—
Wet volume
—
Dry volume
—
Wastage applied
—
| Item | Volume | Mass | Counts | Cost |
|---|---|---|---|---|
| Cement | — | — | — | — |
| Sand | — | — | — | — |
| Water | — | — | — | — |
| Total cost | — |
Coverage per bag at chosen thickness: —
Example Data Table
Coverage per 50 kg bag at common thicknesses (defaults, single side).
| Thickness (mm) | Coverage per bag (m²) |
|---|
Formula Used
- Net area = (sum of segment Length × Height × Qty) − openings.
- If “Both Sides” → Net area × 2.
- Wet volume = Net area × thickness.
- Wastage applied: Wet volume × (1 + Wastage%).
- Dry volume = Wet volume × Dry factor.
- For mix C:S = 1:4, total parts = C + S.
- Cement volume = Dry volume × (C / (C + S)).
- Sand volume = Dry volume × (S / (C + S)).
- Cement mass = Cement volume × Cement density.
- Sand mass = Sand volume × Sand density.
- Bags = Cement mass / Bag size.
- Water mass = Cement mass × w/c. Water liters ≈ Water mass.
- Coverage per bag = ((Bag mass / Cement density) × (C+S)/C ÷ Dry factor) ÷ thickness.
How to Use
- Choose Metric or Imperial units.
- Add wall segments; set openings to deduct; toggle “Both Sides” if needed.
- Enter thickness, wastage, dry factor, and confirm 1:4 mix.
- Optionally adjust densities, bag size, and prices for local suppliers.
- Click Calculate to view materials, costs, and coverage per bag.
- Export results via Download CSV or Download PDF.
FAQs
Wet volume excludes voids and bulking. Dry volume accounts for inter-particle voids and bulking of sand; 1.30–1.35 is typical for plaster mixes.
Yes, 1 part cement to 4 parts sand is common for internal plaster. Exterior or special finishes may use different proportions per specification.
Common single-coat thickness ranges 10–15 mm. Base and finish systems may use multiple coats; follow project drawings and workmanship standards.
Wastage depends on substrate flatness, crew technique, and access. 5–15% is common; increase for rough backgrounds or congested areas.
Yes. Enter local bag mass in kilograms. Coverage per bag recalculates automatically for the chosen thickness.
If you provide price per bag and price per cubic metre of sand, the tool multiplies by required quantities; water is not costed.
This tool assumes a straight cement–sand mix. If using lime, plasticizers, or fibers, adjust dry factor and volumes to match manufacturer recommendations.