Build calculator
How many bags do you need?
Slabs, columns, blockwork and plaster, worked out the way a site engineer would. Results update as you type, and you can add the bags straight to your cart.
How we calculate
The sums, in plain words
So you can check our work, or your contractor's.
Concrete
Wet volume times 1.54 gives the dry materials. Divide by the parts in the mix (5.5 for 1:1.5:3, 7 for 1:2:4) for the cement volume, then use 1,440 kg per cubic metre and 50 kg bags.
Blockwork
Ten blocks per square metre, after removing doors and windows. One bag of cement in a 1:6 mortar lays about 40 blocks.
Plaster
Area times thickness, times 1.27 for dry volume, in a 1:4 mix. Rough walls and thick render need more.
What it leaves out
Water, steel, formwork and labour. Your engineer's design always wins over a calculator.
Ready-mix or hand mix?
When ready-mix costs less
Above about 6 cubic metres, ready-mix usually wins once you count labour, a mixer, water and time.
| For a 15 m³ slab | Hand mix on site | Monolith ready-mix C25 |
|---|---|---|
| Cement | 120 bags, ₦1,182,000 | Included |
| Sand and granite | ₦610,000 | Included |
| Labour and mixer hire | ₦420,000 | Small crew only, ₦120,000 |
| Pump | Not used | ₦185,000 |
| Concrete | Included above | ₦2,220,000 |
| Time on site | 2 days | 4 hours |
| Total, example rates | ₦2,212,000 | ₦2,525,000 with tested strength |
Questions
Calculator questions
Short answers.
Why add 5%?
Spillage, uneven ground and bags left in the rain. Most sites lose more than 5%.
Does the calculator include steel?
No. Your structural drawings give the reinforcement.
Can I save my results?
Add the bags to your cart. The cart stays for this visit, and the customer area keeps your orders.
Got your number?
Add it to your cart and choose a delivery slot.