Free calculator
Concrete calculator
Choose a slab, a footing or post holes, enter the dimensions and see the volume of concrete in cubic metres, cubic yards and cubic feet, plus the number of premixed bags based on the yield printed on the bag.
Concrete calculator
Calculated on lokalmatch.com
Your results
Concrete to order (extra included)
1.36cu yd
Premixed bags
71
- Concrete to order (extra included)
- 1.04m³
- Concrete to order (extra included)
- 36.7cu ft
- Concrete volume
- 1.23cu yd
Estimates for planning only. Confirm quantities with your supplier or contractor before you order.
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How to measure for the concrete calculator
- Slab or pad: measure the inside of the forms (length and width) and the planned thickness.
- Footing: add up the length of every footing run and measure the width and depth of the trench or form.
- Post holes: count the holes and measure their diameter and depth. If a square post will sit in the concrete, enter its width so its volume is subtracted.
- Frost depth and footing sizes are set by the building code that applies where you live: check with your municipality before you dig.
Assumptions behind the concrete calculator
Every default below appears in the calculator and can be changed.
- Slab and footing volume = length × width × thickness. Each post hole is a cylinder: π × (diameter ÷ 2)² × depth.
- Default extra allowance: 10%, for spillage, an uneven base and forms that bulge. It’s our starting point, not a standard; lower it for precise forms.
- Default bag yield: 0.52 cu ft (about 14.7 L) for a 30 kg bag, as listed by Target Products (QUIKRETE in Canada). QUIKRETE’s data sheet lists 0.60 cu ft (17 L) for an 80 lb bag, 0.45 cu ft (12.7 L) for 60 lb and 0.30 cu ft (8.5 L) for 40 lb.
- 1 cubic yard = 0.7646 m³ and 1 cubic foot = 0.0283 m³ (NIST Handbook 44).
- Bags are rounded up to whole bags. Rebar, mesh, the gravel base and forms are not included.
Concrete calculator: tips before you buy
- For larger pours, compare bags with a ready-mix delivery. Ready-mix is ordered by the cubic metre or yard, so use the volume with extra.
- Order a little more rather than less: running short in the middle of a pour can leave a weak joint.
- Compact and level the base before measuring the thickness; low spots use more concrete.
- Wear gloves and eye protection: wet concrete can burn skin.
Concrete calculator: frequently asked questions
How many bags of concrete make a cubic metre?
Divide 1 m³ by the yield of one bag. A 30 kg bag yielding 0.52 cu ft (about 14.7 L) gives about 68 bags per cubic metre; an 80 lb bag at 0.60 cu ft (17 L) gives about 59. Add your extra allowance on top.
How do I convert cubic metres to cubic yards?
Divide by 0.7646, or multiply by about 1.308. The calculator shows both, plus cubic feet.
How thick should a concrete slab be?
It depends on what the slab is for and on the building code where you live: a patio, a shed floor and a garage slab have different requirements. Check with your municipality or a concrete contractor, then enter that thickness.
Is the post subtracted from the hole?
Only if you enter a post width. For tube forms filled completely with concrete, leave that field blank.
Sources for the concrete calculator
We checked these references on September 10, 2026. Product figures vary, so read the label or data sheet of the product you choose.
Last reviewed September 10, 2026
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