How to calculate the right amount of concrete for your project
- The importance of calculating the quantity of concrete
- What to know before calculating the amount of concrete needed
- Use the concrete calculator
- Concrete calculation for different type of projects
- Factors affecting the quantity of concrete to be ordered
- Bagged concrete or mixer rental?
- FAQ
You need to pour concrete for a commercial or residential project? You don’t know how much concrete to order, to make sure there is no waste and incur additional costs?
In this guide, we'll teach you the finer points of using a concrete calculator, and give you tips on how to make sure you buy the right quantity for your projects.
Once you have all the information you need to start your project, Groupe Bellemare offers a wide variety of concrete products and services to meet all your needs.
The Importance of Calculating the Quantity of Concrete
Depending on the size of your project, concrete costs can increase rapidly. An accurate estimate of the quantity of concrete required can help avoid unnecessary expenses.
Ordering as accurately as possible is also more eco-friendly.
- Buying too little concrete will lead to delays and additional costs.
- Ordering concrete in excess will lead to waste and unnecessary expense.
What to Know Before Calculating the Amount of Concrete Needed
Before using the concrete calculator, please gather the following information:
Project Details: Determine the type of project you're working on: a foundation, a paver or a patio, for example. Each project has its own specific requirements.
Measurements: Measure the length, width and thickness of the area where the concrete will be poured. To avoid errors, make sure all measurements are in the same units (e.g., feet, inches or metres).
Concrete Strength: Determine the required concrete strength. This information is usually specified by engineers or described in building codes and regulations.
Use the concrete calculator
The measurement method differs depending on the shape of your future concrete slab. For example, you would measure a rectangular shape using the length and width. A circular shape requires you to find the diameter.
Once you have found the dimensions of your slab, enter them into the calculator and add the thickness. This will give you the amount of concrete needed for your project. You can change the unit of measurement to your preference.
The tool also gives you the amount of concrete needed based on your loss estimate between 5% and 10%.
Concrete Calculation for Different Types of Projects
In residential and commercial construction, concrete is used for a wide variety of projects, from exterior slabs to structural foundations.
Each type of work requires careful planning to determine the amount of concrete needed. Here’s an overview of common projects and key factors to consider when calculating concrete volume:
Concrete Calculation for Slabs
Slabs are used to create flat, solid surfaces such as patios, walkways, driveways, sidewalks, terraces, or garage floors.
-
Features: A standard slab has a thickness of 10 to 15 cm (4 to 6 inches).
-
Calculation: Multiply the length, width, and thickness (in meters or feet) to get the volume in cubic meters (m³).
-
Tip: For harsh winters, make sure the slab is poured over compacted gravel and use a concrete mix designed to resist freeze-thaw cycles.
Concrete Calculation for House Foundations
Foundations are essential for supporting a house or any other building.
-
Features: Typically poured using reinforced concrete, they must comply with the standards of the Quebec Building Code.
-
Calculation: Multiply the length, width, and height of the trenches or foundation walls to determine the required volume.
-
Tip: Add an extra margin to compensate for losses, especially due to uneven terrain.
Concrete Calculation for Walls
Walls, whether poured in place or built with concrete blocks, require precise volume calculations.
-
Features: Poured walls must be properly formworked and are often reinforced with steel bars.
-
Calculation: Measure the height, thickness, and length of the wall to get the needed volume.
-
Note: For interior basement walls, adding insulation and a French drain may be required to prevent moisture problems.
Concrete Calculation for Posts and Columns
Concrete posts are used to support structures like balconies, pergolas, or carports.
-
Features: Dimensions vary, but posts are often poured into cardboard tubes (Sonotubes).
-
Calculation: Use the formula π (pi) × radius² × height to calculate the volume of a cylindrical post.
-
Tip: Always reinforce with steel rebar to ensure strength.
Concrete Calculation for Footings
Footings distribute the weight of a structure to prevent settlement.
-
Features: They are wide, shallow elements typically placed under load-bearing walls or columns.
-
Calculation: Multiply the length, width, and thickness to get the required volume.
-
Quebec-Specific Consideration: Make sure footings are poured on stable soil and below the frost line to avoid seasonal movement.
Factors affecting the quantity of concrete to be ordered
Several factors influence the quantity of concrete required for a project.
Think about losses: It is essential to take into account wastage due to spillage or mixing errors. A common rule of thumb is to add 5-10% waste to the calculated quantity.
Reinforcement: If your project calls for reinforcing the concrete with rebar or mesh, take into account the additional space these materials occupy in the concrete volume.
Irregular Shapes: For non-rectangular or irregularly shaped areas, divide the project into smaller sections that can be measured with basic geometric shapes. Calculate the volume of each section separately and add them together to obtain the total.
Bagged Concrete or Mixer Rental?
Should you order concrete that is already prepared by mixer or is it better to buy your concrete in bags and prepare it yourself?
Larger jobs are easier to accomplish by renting a concrete mixer (rather than trying to mix bag after bag manually). However, for smaller jobs, you should opt for bagged concrete.
Bagged concrete is ideal for:
- Casting of small slabs for sidewalks or patios;
- Installation of fence posts;
- Repair of foundation walls, walkways or steps;
- Casting of small curbs, steps or ramps;
- Bases for decks, pergolas, walls, and more.
If you buy bagged concrete, you will also need additional equipment to mix concrete. A rented mechanical mixer can be very effective!
Concrete delivered by mixer is good for:
- Large patios, walkways, pool decks, and more;
- House foundation slabs;
- Parking lots, sidewalks or any other commercial project.
If you choose delivery by concrete mixers, you will have to calculate the quantity of concrete needed for your work. To avoid additional costs and travel, it is important that the truck carries enough concrete on its first trip. In large projects, several concrete mixers could be deployed and even the use of specialized tools like a concrete pump to spread the concrete more efficiently.
Frequently Asked Questions (FAQ)
How do I calculate the amount of concrete needed for my project?
The calculation depends on the shape and dimensions of the structure you want to build. Multiply the length, width, and height (or thickness) to get the volume in cubic meters (m³). Be sure to add a 5 to 10% margin to account for loss or unforeseen needs.
What’s the difference between an indoor and an outdoor slab?
Outdoor slabs must be adapted to Quebec’s climate conditions, especially freeze-thaw cycles. This includes using a concrete mix specifically designed for frost resistance and ensuring a well-drained gravel base.
Indoor slabs, like basement floors, do not require this additional protection.
Should I include reinforcement in my concrete?
Yes. For structures such as slabs, foundations, or load-bearing walls, adding steel reinforcement (wire mesh or rebar) is highly recommended. It strengthens the structure and helps prevent cracking.
That said, for small, non-structural elements like a shed base or light walkway, reinforcement is not always required but is still recommended for better long-term durability.
How long does it take for concrete to fully cure?
Concrete reaches its initial strength in about 24 to 48 hours, but full curing typically takes 28 days. During this period, it’s important to keep the surface moist to avoid premature drying and cracking.
Can I use an online calculator to estimate my concrete needs?
Absolutely! An online calculator is a convenient tool for getting a quick estimate. Just enter your project dimensions to determine the approximate volume of concrete required.
What type of concrete should I choose for my project?
It depends on the type of structure and its exposure. For outdoor slabs or driveways, a concrete mix that’s resistant to freezing is ideal. For foundations, a high-strength mix is recommended. Consult a professional to choose the best option for your needs.
Calculate your concrete!
If you need more information about your concrete order, do not hesitate to contact our experts!
Our Béton Bellemare sector has been delivering a wide variety of concrete for all types of work for over 50 years.
