Concrete, Slabs & Footings calculator
Estimate concrete volume, buffer, ready-mix order quantity, premix bags, and optional cost for slabs, footings, walls, columns, rings, stairs, or a known volume.
Interactive calculator
Choose the project shape, keep its dimensions in one unit, and compare the ready-mix quantity with a bag estimate based on the yield you enter.
What to do next
Formula, example, assumptions, and FAQs — open any section for the detail.
Volume = length × width or thickness × depth or height × quantityEvery dimension is converted to metres first. Concrete is measured by volume, so slab thickness or wall thickness cannot be omitted.
Cylinder = π × radius² × height × quantity · Ring = π × (outer radius² − inner radius²) × height × quantityEnter diameter, not radius. The ring method removes the hollow inner cylinder from the outer cylinder.
Stair volume = width × run × rise × step count × 0.5 + optional width × platform depth × riseThe optional platform is treated as one riser thick. This is a material approximation, not a stair, waist-slab, landing, or reinforcement design.
Buffer = base volume × buffer % · Total = base + buffer · ft³ = m³ × 35.3146667 · yd³ = ft³ ÷ 27The total with buffer is the ready-mix planning quantity. Supplier minimum loads, order increments, delivery conditions, and actual site loss still need confirmation.
Bags = round up(total volume ÷ cured yield per bag) · Volume cost = total × entered volume rate · Bag cost = bags × price per bagUse the cured concrete yield on the premix package. A cement-bag weight by itself does not state a finished concrete volume. Ready-mix cost and bag cost are alternative routes, not costs to add together.
A small slab is 4 metres long, 3 metres wide, and 0.1 metre thick. One slab is needed, a 10% buffer is selected, the example premix yield is 15 litres per bag, and an optional ready-mix rate of ₹8,000 per cubic metre is entered.
Calculation:Base volume = 4 × 3 × 0.1 = 1.2 m³. Buffer = 1.2 × 10% = 0.12 m³. Total = 1.32 m³ = about 46.62 ft³ or 1.73 yd³. Bags = round up(1.32 ÷ 0.015) = 88. Ready-mix material cost = 1.32 × ₹8,000 = ₹10,560.
Result:Plan around 1.32 m³ after the selected buffer. Confirm the supplier order increment and the actual bag yield before buying. The bag and ready-mix figures are alternatives, and the result does not design the slab or specify concrete grade or reinforcement.
Unit conversion and geometry are deterministic, and bag counts round up to whole bags. Real use can differ because excavation and formwork are not perfectly uniform, dimensions may be approximate, concrete can spill or remain in equipment, and suppliers use their own minimums and order increments. Stair and platform results are deliberately simple approximations. Verify important quantities before a continuous pour.
About 5% may suit a simple, well-measured small pour. A 10% buffer is safer for many home jobs. Complex formwork, uneven excavation, spillage, and measurement uncertainty may justify more. This calculator limits the buffer to 30%; verify unusual work with the contractor or engineer.
Length × width gives area, not concrete volume. Multiplying that area by slab thickness gives cubic metres, cubic feet, or cubic yards. A small thickness error across a large slab can materially change the order.
The interactive shape modes use one selected unit for all active dimensions. Convert mixed measurements first with Unit Converter, or convert the thickness to the selected unit before entering it.
No. It is the calculated material volume after your buffer. Suppliers may have minimum loads, fixed increments, short-load fees, delivery limits, washout rules, or pump requirements. Confirm the final order and site access directly.
The calculator converts the entered cured yield per bag to cubic metres, divides the buffered project volume by that yield, and rounds up. Package yield varies by product, bag size, water content, and local standard, so replace the example value with the bag label.
No. Cement is one ingredient. Finished concrete quantity also depends on sand, aggregate, water, mix proportions, moisture, compaction, and wastage. This calculator does not produce cement, sand, or aggregate quantities or guarantee a mix design.
Yes. It supports metres, centimetres, feet, inches, cubic metres, cubic feet, and cubic yards. The currency field is editable. The default ₹ symbol and metric example can be changed, and no country-specific price is hardcoded.
No. Ready-mix cost uses only the entered rate per cubic metre or cubic yard. Bag cost uses only bag count and price per bag. Delivery, pumping, tax, labour, reinforcement, formwork, equipment, and site preparation are excluded unless already built into the rate you enter.
No. It estimates material volume only. It does not determine member dimensions, loads, concrete grade, reinforcement, cover, foundations, curing, formwork, or structural safety. Structural work requires appropriate drawings and professional review.
This calculator provides a material volume and optional cost estimate only. It is not a structural design, RCC design, mix design, concrete grade recommendation, reinforcement or steel calculator, labour-rate database, supplier quote, or safety guarantee. Confirm dimensions, bag yield, concrete specification, delivery conditions, and structural work with the relevant engineer, contractor, supplier, drawings, and local requirements.Read the full disclaimer.