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Concrete Calculator — Slabs, Columns & Bags

Work out how much concrete to order for a rectangular slab, round column or hollow tube. Choose your measurement unit, enter the dimensions, and add your own waste allowance. Results show cubic metres, cubic yards and cubic feet together. For bagged concrete, enter the mixed yield printed on the bag; for a cost estimate, add your supplier's price. A 5 m × 4 m × 0.15 m slab needs 3 m³ before waste, or 3.15 m³ with a 5% allowance. These are quantities to check with a supplier, not structural specifications.

No account Formula visible Your rate and units

Use your evidence

What to have beside you

Use the current bill or tariff sheet, exact product label, location-specific solar estimate, or measured project dimensions. Example physical values teach the tool; zero money rates prevent an unsourced price from becoming a default claim.

USUSA GBUK AUAustralia AEUAE CACanada EUEU NZNew Zealand SGSingapore

Enter your details

Your values

Every input includes a simple explanation.

Simple wordsFormula shownPrivate inputs

Simple viewUsing editable example assumptions for technical settings.

Concrete shapeUser-entered value — example shownChoose the shape of the space you want to fill with concrete.

Dimension unitUser-entered value — example shownThe measurement unit used for the dimensions you are entering.

Helpful tip: All active dimensions use this unit. Re-enter measurements if you change it; existing numbers are not converted.LengthUser-entered value — example shownThe end-to-end measurement of the wall, room, slab, bar, or surface.

WidthUser-entered value — example shownThe side-to-side measurement of the room, slab, tank, or surface.

Depth or heightUser-entered value — example shownUse slab thickness for a slab, or vertical height for a column or tube. All dimensions use the unit selected above.

Identical sectionsUser-entered value — example shownHow many identical appliances, elements, fans, or slabs you want to include.

sections

Waste allowanceUser-entered value — example shownExtra concrete volume allowed for spills, uneven excavation and small measurement differences.

Order and quote unitUser-entered value — example shownThe unit in which you want the final result shown.

Helpful tip: The ready-mix price below must be quoted per this volume unit.Mixed concrete from one bagUser-entered value — example shownCopy the finished mixed volume from the product bag or technical sheet. Leave 0 to skip bag estimates. Bag weight alone is not enough.

m3/bag

Bag yield unitUser-entered value — example shownMatch the unit printed beside the product's mixed volume. For example, 0.6 cubic feet is entered as 0.6 with cubic feet selected.

Ready-mix quote per order unitUser-entered value — example shownEnter your supplier's price for one cubic metre, yard or foot, matching the order unit above. Leave 0 until you have a quote.

USD/m3

Price per bagUser-entered value — example shownEnter the price of one bag of the product whose mixed yield you entered. Leave 0 to skip this cost.

USD/bag

CurrencyUser-entered value — example shownThe currency used on your bill or quote. It changes the symbol, not the formula.

Helpful tip: Choose the currency printed on your bill or quote. No exchange-rate conversion is performed.

Private: calculations run in your browser; a saved scenario stays on this device.

Your result

Concrete volume

3.15 m³

The order volume includes your allowance. Ready-mix and bagged-mix costs are alternative material estimates, not amounts to add together.

Cubic metres3.15 m³

Cubic yards4.12 yd³

Cubic feet111.241 ft³

Before waste3 m³

Whole premix bagsEnter product yield

Ready-mix material costEnter supplier quote

Bagged material costEnter yield and bag price

Confirm dimensions, concrete specification and ordering allowance with the responsible professional and supplier. This is preliminary quantity only.

Preliminary quantity only. This result is not structural design, reinforcement approval or a safety instruction.

How this was calculated

Formula used

Slab = length × width × depth; solid round = π × diameter² ÷ 4 × height; hollow tube = π × (outside diameter² − inside diameter²) ÷ 4 × height. Order volume = shape volume × quantity × (1 + waste% ÷ 100). Bags = round up(order volume ÷ mixed yield per bag). Material cost = order volume × quoted price, or whole bags × bag price.

Your values in the formula

5 m × 4 m × 0.15 m × 1 × (1 + 5%) = 3.15 m³.

Assumptions and rounding

Selected shape: slab. All dimensions convert to metres before calculation.
Bag count rounds up using the mixed-concrete yield printed on your product, not its dry weight.
Only entered prices are used. Delivery, labour, tax, supplier minimums and structural design are excluded.

Excavation tolerance, uneven sub-base, formwork, site access and supplier minimums can change the order. A qualified professional must approve structural work.

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What the result means

Use it as a scenario

Excavation tolerance, uneven sub-base, formwork, site access and supplier minimums can change the order. A qualified professional must approve structural work.

A 5 m × 4 m × 0.15 m slab is 3 m³ before the entered waste allowance.

What can change

Check before deciding

01All active dimensions must use the selected input unit; diameter is not radius.
02Use mixed yield from the exact bag, not a generic bag-size assumption.
03Ready-mix and bagged-mix costs are alternatives; taxes, delivery and labour are excluded.
04Quantity estimation is not mix design, reinforcement design or code approval.