Concrete pack: estimate, check, and order

A complete slab job in one page for Canadian contractors, renovators, and serious DIY builders. Run the calculator, work the pre-job checklist, fill in the material list in purchasable units, and take the print page to the truck or the supplier counter. All results are estimates.

Standalone calculator: Concrete estimator on the BuildTrue home page. This hub bundles the same math with the job paperwork around it.

Concrete calculator

For a rectangular slab. Enter length, width and depth in the selected system. This section is a full duplicate of the standalone concrete calculator logic, adapted as a self-contained section for this hub page. See the integration note for the reasoning.

Canada default is metric. Switch at any time: the values on screen convert so the physical size stays the same. Results show both systems.

Slab length (m)

Slab width (m)

Slab depth (mm)

Waste allowance (percent)

Formula: volume = length x width x depth. Volume with waste = volume x (1 + waste / 100). Bags = ceiling of (volume with waste / 0.0135). Bag yield stated: one 30 kg pre-mix bag yields about 0.0135 cubic metres. 1 cubic metre = 1.30795 cubic yards. Whole counts use an epsilon safe ceiling.

Worked example: Length 6 m, width 4 m, depth 100 mm (0.1 m), waste 10 percent. Volume = 6 x 4 x 0.1 = 2.40 cubic metres. With waste = 2.64 cubic metres (3.45 cubic yards). Bags = 2.64 / 0.0135 = 195.56, rounded up to 196 bags. Full arithmetic is in the worked example file in this pack.

Estimates only. This is not engineering or code compliance advice. Verify quantities, mix, reinforcement and local requirements with a qualified professional before ordering or pouring.

Pre-job checklist

Site prep

Confirm access for the delivery or for bag mixing: truck reach, wheelbarrow path, and washout location agreed with the owner.
Excavate to firm, undisturbed soil or compacted granular base. Soft spots dug out now are cheaper than cracks later.
Set forms level or to the planned slope, braced so a loaded screed or a bumped form does not move mid pour.
Plan the pour sequence, the screed method, and who is finishing, before any concrete is ordered or mixed.
Check the forecast. Rain, high heat, and overnight frost each change the plan for placing and curing.

Measurements to confirm

Slab length and width inside the forms, measured in two places each.
Slab depth, checked with a depth gauge or a marked stick at several points across the base.
Any thickened edges, pads, or steps that add volume beyond the simple rectangle.
Waste allowance. Ten percent is the calculator default; irregular bases and hand mixing argue for more.
If ordering ready mix, the supplier minimum load and the short load fee, confirmed before the pour day.

Permits and code notes for Canada, general level

Slabs that support a structure, a garage, or a dwelling addition commonly need a permit and inspections in Canadian municipalities. Flatwork such as a walkway often does not, but the rule is local.
Reinforcement, air entrainment for freeze and thaw exposure, and control joint spacing are specification matters set by the design and local practice, not by this estimator.
General information only, not code advice. Confirm local code and permit requirements with your municipality and a qualified professional before you build.

Permits and code notes: General information only, not code advice. Confirm local code and permit requirements with your municipality and a qualified professional before you build. Estimates only. Verify quantities, layout, and local requirements before ordering or building.

Material list template

Concrete material list template. Quantities are in purchasable units. Fill in the quantity column from your calculator result, then confirm your waste allowance before you order.

Item	Specification or size	Purchasable unit	Quantity	Notes
Pre-mix concrete	30 kg bag, yield about 0.0135 cubic metres per bag	Bag	____	Calculator bag count already includes your waste allowance.
Ready-mix concrete	Mix and slump as specified for the job	Cubic metre, ordered to supplier increment	____	Alternative to bags. Confirm minimum load and short load fees.
Granular base	Compacted granular material	Cubic metre or tonne, as the yard sells it	____	Depth after compaction, not loose depth, sets the volume.
Reinforcement	Rebar or welded wire mesh as specified	Piece or roll	____	Add laps and chairs. The slab calculator does not count steel.
Form lumber and stakes	To suit slab depth and length	Piece	____	Reusable on many jobs. Count what this job needs on site.
Control joint and finishing consumables	Curing compound, joint filler as specified	Container	____	One container rarely covers a surprise second slab. Check coverage on the label.

Print the companion checklist page in this pack for a paper copy you can take to the supplier counter.

Pro tips

Order or stage for the full pour plus waste, and never plan to stretch a load by adding water on site. Extra water trades strength for workability you will regret.
Do a dry run of the screed path with the actual crew. Most pour day problems are access and sequence problems, not concrete problems.
Check depth at the centre of the slab, not only at the forms. Bases dish in the middle, and a thin centre is where cracks start.
Keep one person on water and curing from the moment finishing ends. The first hours decide more of the surface quality than the mix does.
Write the bag count or load size, the weather, and the finish time on the job sheet. That record is gold when a client asks about a crack months later.
For bag work, stage bags around the mixer before you start and count empties as you go. Counting empties is the only reliable progress meter mid pour.

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Print version: Concrete checklist and material list for print. Worked example: Concrete worked example with hand checked numbers.