Concrete Calculator MX
Estimate the volume of concrete you need for a slab or footing, in cubic metres, feet and yards.
How it works
Enter the length, width and thickness of the slab and how many you are pouring. The calculator returns the volume in cubic metres, feet and yards, adds a 10% waste allowance, and can estimate bags if you provide the yield per bag.
Frequently asked questions
How much concrete do I need?
Multiply length by width by thickness in the same units. A 3 m × 3 m slab 0.1 m thick is 0.9 m³ (about 1.18 cubic yards). Add 5–10% for waste.
How many bags of concrete per cubic metre?
It depends on bag size. A 25 kg bag yields roughly 0.0125 m³, so about 80 bags make up one cubic metre — which is why larger pours use ready-mix.
How do I calculate cubic yards of concrete?
Work out the volume in cubic feet (length × width × thickness in feet) and divide by 27. For example, 24 cubic feet ÷ 27 ≈ 0.9 cubic yards.
When should I use ready-mix instead of bags?
Bagged concrete is fine for small jobs, but around a cubic metre or more it is usually cheaper, faster and more consistent to order ready-mix delivery.
How much concrete for fence posts?
For a round hole, volume = π × radius² × depth; subtract the post volume if you want to be precise. Multiply by the number of posts and round up.
How much extra concrete should I order?
Add about 5–10% to your calculated volume to allow for spillage, an uneven base and over-dig on footings.
What is a concrete estimator?
It is a tool that turns slab or footing dimensions into a concrete volume, then into the number of bags or the ready-mix quantity to order.
Concrete Calculator
Ordering the right amount of concrete matters: too little stops a pour halfway, too much is wasted money. This estimator works out the volume from your dimensions — below is how it is calculated and how to turn volume into bags or a ready-mix order.
How much concrete do I need?
Volume = length × width × thickness, with every measurement in the same unit. Metres give cubic metres (m³); feet give cubic feet, which you divide by 27 for cubic yards.
Worked example (slab)
A 3 m × 3 m slab, 100 mm (0.1 m) thick: 3 × 3 × 0.1 = 0.9 m³. That is about 1.18 cubic yards.
Bags or ready-mix?
Bagged mix suits small jobs; for anything around a cubic metre or more, ready-mix delivery is usually cheaper and faster. As a rough guide, a 25 kg bag yields about 0.0125 m³, so 0.9 m³ needs roughly 72 bags — a clear sign to order ready-mix instead.
| Bag size | Approx. yield |
|---|---|
| 25 kg | ~0.0125 m³ (12.5 L) |
| 40 lb | ~0.30 cu ft |
| 60 lb | ~0.45 cu ft |
| 80 lb | ~0.60 cu ft |
Footings, posts and columns
For trenches and footings use the same length × width × depth. For round post-holes or columns, volume = π × radius² × depth. Always round up.
Add a waste allowance
Add about 5–10% for spillage, uneven sub-base and over-dig, especially on footings, so you are not caught short mid-pour.
Results are estimates for general guidance in Mexico and may not reflect the latest local rates, fees or rules. Check official sources before making decisions.