How to Calculate the Amount of Sand: Practical Guide
By David Polido, CEO of Chambino Areias and INERCORChambino Areias supplies sand in Portugal only (Seixal, near Lisbon). Prices exclude VAT; delivery to site from 5 t across the Lisbon and Setúbal region; smaller orders are collected at the pit.
Why is Calculating Correctly Important?
Calculating the correct amount of sand is crucial for several reasons:
- Cost savings: Avoid buying more than necessary
- Waste prevention: Reduce environmental impact
- Project planning: Better budget control
- Space: Avoid storage problems
- Quality: Ensure correct proportions in mixes
Basic Formula for Calculation
Volume (m³) = Length × Width × Thickness
For sand, add a safety margin of 10-15%
Important Units:
- 1 m³ (cubic metre) = 1,000 litres
- 1 m³ of dry, loose sand ≈ 1.6 tonnes ≈ 64 bags of 25 kg
- 1 tonne of sand ≈ 0.63 m³
- 1 Big Bag = 1 tonne = approx. 0.63 m³ = 40 bags of 25 kg
- One 25 kg bag = approx. 0.016 m³ (16 litres)
Quick answer: 1 m³ of sand ≈ 1.6 t. Big bags are counted by weight, not volume: 2 m³ = 3.2 t ≈ 4 big bags (one per tonne, rounded up).
Need the cement too? See how much sand and cement you need: per bag of cement, per m² and per tonne of sand.
Calculation by Type of Application
1. Site-mixed concrete (non-structural slabs and paths)
Site-mixed concrete, ≈ 1:2:3 by volume (no strength class implied):
- 1 part cement
- 2 parts sand
- 3 parts crushed stone
Practical calculation:
- For 1 m³ of concrete: 350 kg of cement (14 bags of 25 kg, ≈ 0.24 m³)
- Sand: approximately 0.48 m³ of coarse washed sand 0/4 (≈ 770 kg)
- Crushed stone: approximately 0.71 m³
Note: the C20/25 class is defined by compressive strength (EN 206), not by the mix. A 1:2:3 mix is an estimate for site-mixed concrete; for structural concrete (footings, columns, slabs), ready-mix concrete is recommended.
Chambino Areias does not sell crushed stone (gravel) for concrete. Our washed gravel 8-12 mm has no CE marking; its product sheet allows it only in blinding or fill concrete with no load-bearing function.
Example:
Slab 10m × 5m × 0.15m (thickness)
Volume = 10 × 5 × 0.15 = 7.5 m³ of concrete
Sand needed = 7.5 × 0.48 = 3.6 m³ ≈ 5.8 tonnes
Cement = 7.5 × 14 = 105 bags of 25 kg
With a 10% margin: ≈ 6.3 tonnes of sand
Approximately 7 Big Bags of sand (a slab is structural: ready-mix concrete is the safer choice)
2. Mortar for Masonry
Masonry mortar (1:4):
- 1 part cement
- 4 parts sand
Simplified calculation:
- Per m² of 11 cm brick wall (1 cm joints): approximately 26 kg of mortar, about 0.013 m³
- Per m³ of mortar: approximately 1 m³ of loose sand (≈ 1.6 tonnes), because water and cement fill the voids
- So: about 0.013 m³ of sand (≈ 21 kg) per m² of wall
Example:
Wall 20 m² in 11 cm brick
Mortar = 20 × 0.013 = 0.26 m³
Sand needed = 0.26 m³ ≈ 420 kg; with a 10% margin ≈ 460 kg
Approximately 19 bags of 25 kg (or 1 Big Bag)
This is below the delivery minimum: an order this size is collected at the pit in Seixal.
3. Rendering and Plastering
Render in two coats:
- Base coat (≈ 1.5-2 cm): 1 part cement to 5 parts washed sand 0/4 (in practice 1:4 to 1:5)
- Finish coat (≈ 0.5 cm): 1 part cement to 5-6 parts fine washed sand 0/1
Practical calculation:
- Rule of thumb: about 16 kg of loose sand per m² for each cm of thickness
- Base coat (1.5 cm): ≈ 24 kg/m² of washed sand 0/4
- Finish coat (0.5 cm): ≈ 8 kg/m² of fine sand 0/1
Example:
Wall 50 m² to render (1.5 cm base coat + 0.5 cm finish coat)
Base coat: 50 × 24 kg = 1,200 kg of washed sand 0/4; with a 10% margin ≈ 1.3 tonnes
Finish coat: 50 × 8 kg = 400 kg of fine sand 0/1; with a 10% margin ≈ 440 kg
Approximately 2 Big Bags of washed sand 0/4 and 18 bags of 25 kg of fine sand 0/1
About 1.7 t in total, below the delivery minimum: an order this size is collected at the pit in Seixal.
4. Floor Screeds
Screed mortar (1:3 to 1:4):
- 1 part cement
- 3-4 parts coarse washed sand 0/4 (never fine sand)
Practical calculation:
- Per m³ of screed: approximately 1 m³ of loose sand (≈ 1,600 kg) and 325 kg of cement (13 bags)
- Per m² (5cm): approximately 0.05 m³ of sand, about 80 kg
Example:
Room 30 m² with 5 cm screed
Volume = 30 × 0.05 = 1.5 m³ → sand ≈ 1.5 m³ = 2.4 tonnes
Cement = 1.5 × 13 ≈ 20 bags of 25 kg
With a 10% margin: ≈ 2.6 tonnes of sand
Approximately 3 Big Bags of coarse washed sand 0/4
Quick Reference Table
| Application | Mix | Sand per m² |
|---|---|---|
| Concrete (site-mixed) | ≈ 1:2:3 | 0.48 m³ (≈ 770 kg) per m³ of concrete |
| Masonry mortar (11 cm brick) | 1:4 to 1:5 | ≈ 21 kg/m² |
| Rendering (1.5 cm base + 0.5 cm finish) | 1:5 (base) / 1:5 to 1:6 (finish) | ≈ 24 + 8 kg/m² |
| Floor screed (5 cm, sand 0/4) | 1:3 to 1:4 | ≈ 80 kg/m² |
Important Tips
1. Always add a safety margin
Add 10-15% extra to your calculation to compensate for losses, spills and irregularities in the surface.
2. Consider moisture
Wet sand weighs more: 1 m³ can reach about 1,900 kg. The conversions above are for dry, loose sand (≈ 1,600 kg/m³).
3. Choose the right format
Big Bags: Larger jobs (>1 tonne)
25kg bags: Small works or easier transport
Bulk (washed 0/4 only, from 5 t): large jobs
4. Consult professionals
For structural or complex projects, follow the designer or site engineer. For quantities and formats, contact us.
Common Errors to Avoid
- Forgetting the safety margin: Always add 10-15% extra
- Confusing units: Check if calculations are in m², m³, kg or tonnes
- Not considering thickness: Crucial for screeds and renders
- Ignoring surface irregularities: Uneven surfaces need more material
- Buying excessive quantities: Surplus sand takes up space on site and has to be protected from rain and dirt
Conclusion
Calculating the correct amount of sand is essential for the success of your construction project. Use the formulas and examples in this guide, or the simulator, for a quick estimate; for structural work, follow your designer or site engineer.
Chambino Areias supplies sand in Portugal only, from Seixal (near Lisbon). Delivery to site is from 5 t across the Lisbon and Setúbal region (outside it, on request, also from 5 t); smaller orders are collected at the pit. Contact us with your quantities and we will send a quote.
Need Help With Your Calculation?
Contact us with your measurements to estimate the amount of sand and choose the format.
Chambino Areias supplies sand in Portugal only (Seixal, near Lisbon). Prices exclude VAT; delivery to site from 5 t across the Lisbon and Setúbal region; smaller orders are collected at the pit.