Concrete Calculator - How Much Concrete Do You Need

When it comes to construction, concrete is man's commonly used material on earth. It's a crucial part of any buildings, roads, dams, and bridges. Furthermore, it also uses a range from different structural applications to drains, curbs, and paviors.  

Although it's mainly for construction, Egyptians first developed a material identical to concrete over a thousand years ago. Consisting of lime and gypsum, they improved this plaster-like material by combining it with other substances. Thus, morphing into the modern concrete that we know today.  

Benefits of concrete

Now, concretes have numerous positive aspects, which makes it ideal for any construction project. A few of its benefits include the following:

Low maintenance. Unlike other alternative building materials, concrete can last for decades, even when it's barely maintained. Because of it, you barely have to spend anything when it comes to maintaining it. Even more, it reduces your environmental footprint since you require less reconstruction to retain it.

Highly resilient. Concrete isn't' susceptible to rust, burn, or even rotting. It's also resilient against fire, water, and wind, which is why most people prefer to use it over other conventional building materials.

Power-efficient. Concrete buildings can moderate the temperature conditions inside the building. Thus, reducing the need for heating and cooling over its service life. When combined with other technologies such as hydronic heating, concrete can boost energy efficiency by up to 70%.

Versatile. Although many people consider it as durable and highly resilient, freshly mixed concrete allows you to design it in any way you want. It means that you can shape it in any form you wish to. You can even change the surface and the texture, too.

Characteristics of concrete

The type of cement and the method used to produce it determines the characteristics of concrete. 

Density: When it comes to ordinary structural cement, the water-to-cement ratio determines its strength. So, regular structural concrete with lower liquid content can cause it to become stronger. It also means that the less porous the concrete will be, the better its performance. Thus, making it more durable for various construction projects. However, reducing the water can only affect its workability. To know how much water you need, using the slump test to measure it should do the trick.  

Durability: Concrete is highly resistant to any physicochemical effects from the environment. That's why it's highly suitable for structures that often get exposed to extreme conditions.

Mechanical Strength: When it comes to the concrete's power, you can measure it through MPa. MPa compares to a force of 50 tonnes on a square with sides of ten centimeters. Standard concrete can vary between 24 and 40 MPa. Meanwhile, High-Performance Concrete commonly has 50 MPa. 

Strengthening the concrete

Various factors can affect the strength of concrete. Aside from moisture, the temperature can affect its durability, too. So, if you want to improve its performance, adding metal rods, cables and wires can help. 

Meanwhile, if you're using concrete where there are very high tensile stresses, adding pre-tensioned steel wires is the best way to go. Doing so creates a compressive force that can offset the tensile forces placed on the structure.

Meanwhile, you can integrate sacrificial probes within the concrete to add more strength. Thus, improving its performance.

Concrete Calculator Formula

When it comes to estimating the right amount of concrete for your project, getting the correct equation is necessary. To help you calculate concrete, here are a couple of steps that you can follow:

1. Establish the right thickness that you want the concrete to have.
2. Get the right length and width of the area that you want to cover.
3. Multiply the length by width so that you can get the correct square footage.
4. Convert the thickness of the concrete from inches to feet.
5. After your conversion, multiply the concrete's thickness in feet by the square footage to get cubic feet.
6. Convert cubic feed into cubic yards. You can do so by multiplying it by .037.

Example:

1. 10 x 10 = 100 square feet
2. 4 ÷ 12 = .33
3. 100 x .33 = 33 cubic feet
4. 33 x .037 = 1.22 cubic yards

Now, the formula is ideal for solving for volume and then converting it to cubic yards. For concrete, the procedure for volume is as follows: length x width x thickness.

You need to divide the total cubic yards that the yield needs to determine the number of concrete bags you need.

Use the following yields per each bag size:

• 40-pound bag yields .011 cubic yards
• 60-pound bag yields .017 cubic yards
• An 80-pound bag yields .022 cubic yards

Ready Mixed Cement vs. Bagged Concrete

What is Ready Mixed Cement?

Ready-mixed cement, or otherwise known as ready mixed concrete, are construction materials manufactured in a plant and delivered to a particular construction site in a plastic state. These are primarily unhardened and ready for use, making it an ideal choice for many projects.

Many say that ready-mix cement performs much better for various projects, despite its expensive cost. Even more, it provides a better-quality output, too. The variation between batches is also minimal when you get concrete prepared in a plant setting. Ready-mix cement is highly advisable for large construction projects that need high volume.

Ready-mixed concrete by the yard is suitable for:

• Large patios, driveways, pool decks, and more
• Foundation slabs for a house
• Parking lots or commercial sidewalks

If you're planning to order concrete from a ready-mix supplier, they'll need to know how many yards of concrete to deliver. Many ready-mix companies will have a minimum order of 1 yard and charge shortage fees when ordering partial batches. The average truck holds between 9 and 11 yards total. If your project requires more concrete, multiple trucks will be necessary.

What is cement bag concrete?

If you plan to use cement bags on a pallet, all you need to do is prepare water and a hoe to activate it. However, it'll only be just as strong as you want it depending on the amount of water you put in mixing it.

Larger jobs such as driveways are easier to complete when ordering concrete by the yard than mix bag after bag by hand. For smaller jobs, like a walkway, modest patio, or footings, you should calculate the number of concrete bags instead.

Bagged concrete is ideal for:

• Pouring small slabs for sidewalks or patios
• Setting posts for fences or mailboxes
• Pouring columns
• Making repairs to foundation walls, walkways, or steps
• Pouring small curbs, steps, or ramps
• Footings for decks, pergolas, walls, and more

If you're purchasing bagged concrete, you may be able to have it delivered. But if it is only a few bags, you'll be responsible for transporting it yourself. You'll also need additional equipment for mixing the concrete. A rented mixer can be very helpful, but a wheelbarrow works for just a few bags.

Understanding a few facts about ready-mixed cement and bagged concrete

Ready-mixed cement:

• It comes in small bags, which only needs to get mixed with the appropriate water ratio as required. The mix will remain usable as you as you keep it dry.
• You can buy a small tub of ready-mixed cement and use it as a paste. It will harden as soon as it gets exposed to air. You need to ensure that the lid is tight so you can use it for other projects.
• You can make your cement waterproof by buying sealants or other additives.
• White cement is ideal for rendering projects, especially if you want to give it a fresher finish.
• Grout that people use when installing tiles is another type of ready-mixed cement.

Concrete bag:

• You can create a concrete mix on your own. So that you can get a smooth finish for your project, you must use an appropriate mixer to do the job. Meanwhile, for creating a concrete base, a coarser aggregate and a little bit of mixing should do the trick.
• Concrete bags are ideal for those who are looking for a smooth finish. It also has a reliable drying time, which means you don't have to wait any longer than what's indicated in the package.
• Since concrete bags are essentially a mixture of cement and other supplies, you can create different finishes, depending on your needs. For example, you can use reinforced concrete when creating watertight structures like tunnels and underpasses.

Concrete Estimating Tips

Estimating concrete costs

Doing an estimate of new concrete costs requires more than just knowing the concrete price for every yard. It would be best if you thought about surface prep, reinforcing materials, formwork, and finish work, too. On top of that, you should also consider the costs of ready-mix concrete. To get a rough estimate of all the costs, you need to consider a couple of factors to ensure its success.

Ready-mix concrete cost per yard

Whether you'll be using ready-mix concrete or other concrete mixtures, an essential item you need to consider is its price. You can ask any of your local ready-mix concrete suppliers for quotes once you've established the project specifications and the site location. Local suppliers often quote their prices based on the cubic yard or cubic meter.

Concrete Sub-grade work cost

If you're planning to place concrete on top of the soil, you'll need to either prepare its surface or grade it for the concrete. You can determine the pricing of concrete sub-grade work in most scenarios once you consider the other expenses related to excavating, grading, trenching, and compacting the soil.

Site work or extra sub-grade

There are times when a construction surface isn't as flat and even as you want it to be. If that's the case, then you need to spend some more for additional site work. It can either include filling it with suitable material or removing any soft spot to make it ideal for construction. 

Cost of concrete formwork

Constructing formwork commonly amounts to a signification portion of the concrete work's entire cost. That's why you must first determine the formwork type that you'll use for your project before starting it. It's best to distinguish the formwork type you'll use, its installation process, and whether you'll buy or rent the form materials. Meanwhile, other associated costs can include renting equipment such as a crane to move and form materials. These machines can also create release products and re-using form material.  

Finish concrete cost

Concrete prices can change depending on the finishing or the concrete type that you need in your project. You can finish concrete in various ways. It can either be smooth, stamped, or exposed aggregate, depending on what you need. Some may only require a strike-off elevation. Meanwhile, others can also choose from troweled, floated, and broomed. To get an estimated finish, you can consider adding $0.75 per square foot or more, depending on the finish's complexity.

Concrete reinforcement cost

Most concrete projects always have some form of reinforcement to add to its stability. It can either be wire or plastic mesh, rebar, or even fiber added into the mix to boost its strength. Even more, adding reinforcement material can make less susceptible to cracks, too. Primary reinforcing materials approximately cost $0.18c for every square foot. However, it can be more expensive, depending on the rebar's height or other reinforcement types.

Calculating the amount of concrete needed for slabs (including odd shapes)

Rule of thumb: add 1/4" to the thickness of your slab for your slab concrete budget. This calculation assumes you have the job evenly graded to the right depth, and the grade is well compacted.

If you check your grade and one spot is 4", some areas are 4.5" to 5"-the best solution for both the job quality and your concrete budget is to fix the grade.

Odd shapes: Transform odd shapes into rectangles, and irregular shapes are suddenly easy to figure.

Figure driveway 14' x 20', and your estimate will be okay. Here is why: The driveway is 16' at the top and 12' at the bottom. Through the center, the width averages 14'.

Calculating the amount of concrete needed for footings

Footings will rarely follow the drawing strictly. In rocky soil, the foundations may collapse when big rocks get excavated.

It was supposed to be a 12"*12" footing but note how the footing's left side has collapsed. Calculate the correct width.

The excavator may have dug too deep, or it may have rained, and footings needed to get dug out deeper to reach firm soil. So, it is essential to check a variety of spots on your footing and get an average size. Then use the calculator to figure the amount of concrete needed.

House slabs on grade 8" out of grade with a 4" slab also have some grade footings.

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This 12" x 12" footing needs to get calculated 12" x 16" so the footing is figured to go above grade to reach the 4" slab thickness.

Estimating concrete steps

Steps seem tricky to calculate but are not. If three steps are leading up to a porch:

• Use the slab calculator to figure the concrete needed for the porch surface.
• Use the footing calculator to calculate the sides of the porch and the steps.

Here is an example:

This porch has nine sq. feet of porch surface, so enter the slab calculator 4" thickness by 3' width by 3' length. It totals .11 cubic yards.

The porch also has nine linear feet of 6" step. So, enter in the footing calculator, 6" depth by 12" width (always figure measures with a 12" width) by 9' length. It totals to .17 cubic yards.

The total concrete needed for the 3' by 3' porch will be .28 cubic yards. (.11 + .17 cubic yards = .28 cubic yards)

Repeat this for added layers of steps.

Calculating the amount of base fill

Granite Construction has an excellent base fill calculator on their site. Use this to figure how much material you need for the subgrade.

Using a Margin of Safety: Problems Caused by Underestimating the Amount of Concrete

Never try to order the exact amount of needed concrete. Include a margin of safety.

A perfectly placed order of concrete will finish the job with a small amount of leftover. A 20 cubic yard order with one cubic yard left over is a good order. A 20 cubic yard order that comes up a cubic yard short is not good.

Six common concrete problems and how to fix them

When it comes to construction, concrete contractors are a few of the most in-demand stakeholders in any project. That's because concrete still is a popular material when it comes to building structure. Because of its versatility and endurance, most contractors still prefer to use concrete up until today. However, the process of using concrete isn't all that easy. There are times that things don't usually go as planned, which can affect the overall output of the project.

No matter how easy concrete is when used, concrete can degrade as the year’s past. Fortunately, there are ways to help you slow down its wear and probably even fix the damages.

Concrete issues can vary from discoloration, scaling, and other various challenges. That's why it's crucial to conduct routine inspections to resolve the problem before it gets worse.

The list will cover the primary concrete challenges as well as how to solve them. Even more, it can even preserve the appearance of your structure as well as its durability.

Cracks

Cracks are one of the most common problems that people encounter when working with concrete. If not resolved, these cracks can seep into the bottom of the slab after a couple of months. Then, it'll reach through the subgrade. Thus, affecting the stability of the project. To fix these issues, you need to replace the concrete structure entirely.

As soon as you see any small cracks, you can fix it by cleaning any loose material out of the damaged areas. Then, you can fill it with concrete filler to restore its appearance. Also, applying a sealant product once the patch has cured can help strengthen it.

Crazing

Another common issue when it comes to working with concrete is crazing. It's a network of tiny cracks found in the concrete's surface. It often occurs when you use an improperly mixed or cured cement during the installation process. Although these cracks won't work their way into the structure's foundation to create an impact, the fine lines can reduce the property's aesthetic value.

To prevent crazing from happening, concrete contractors often perform a quality installation process. However, if it occurs on an aesthetic indoor concrete structure, you may still fix it by applying a layer of epoxy paint to cover the cracks. Unfortunately, surface hardeners and sealers can make the cracks appear more noticeable. So, it's only practical to add a layer of resurfacing concrete to cover it.

Discoloration

There are times when concrete can also have light or dark patches because of improper installation techniques. Stains from materials such as automobile fluids and cleaning chemicals can cause it, too. So, as soon as you notice any stains or discolorations, it's best to address it as quickly as possible. Doing so will prevent the stains from seeping in and spreading throughout the entire concrete slab.

You can scrub the stained part with a stiff brush that's dipped in a diluted vinegar solution. Doing so will somehow halt the stains' progression and might even restore it to its original appearance. Meanwhile, more potent chemicals like diammonium citrate or hydrochloric acid can do the job for severe discoloration problems. However, since these solutions are too strong, it's always ideal to ask help from an expert before using any of them. 

Scaling

Scaling often occurs during winter months, primarily when you use de-icing salts on concrete. Although it's an effective way to eliminate all the ice, it'll slowly lose the surface material and continue until the damaged areas get repaired. One effective way to solve this problem is by adding a new layer of resurfacing concrete. Once you've completed applying the new concrete layer, you need to let the material cure for at least 24 hours. Then, the contractors will use a waterproof finishing treatment for additional protection.

Buckling

Another issue that you might encounter is buckling. If there are massive trees around the property, there's a big chance that the roots will grow under the structure. Thus, causing the slab to split apart. The same case can happen when the slab gets exposed to extreme freeze-thaw cycles and heat exposure. To fix the issue, you need to get rid of the concrete's damaged part, along with the roots that might have caused the damages. Next, the concrete contractors will install a large patch to protect the buckled area from cracking and splitting.

Curling

Concrete curling happens when there's a sudden shift in moisture and temperature of the concrete slab's top and bottom surface. Once this happens, there’s a chance that the concrete slab's surface can lose its support from the base. To prevent it from happening, concrete contractors should use proper curling techniques. They can place the joints correctly. Then, they can either use water-reducing admixtures or low water content with the largest possible aggregate size. Once it's complete concrete contractors can guarantee that the slab has properly bonded once they apply thin topping mixes. It's essential to use just the right amount of topping combinations when reinforcing steel in the concrete slab. Doing so will make it look more polished and cleaner. Finally, they need to place the concrete on a damp but absorptive sub-grade. Putting it in an absorptive sub-grade will prevent the bleed water from getting to the top of the slab.

Extra costs of coming up short of concrete

• Overtime for the crew
• A short load charge from the ready-mix supplier
• A cold joint can occur (where one pour ended, and another pour began)

Three steps to ordering enough concrete:

• Use the concrete calculator to calculate how much concrete you need.
• Figure depths and widths have been built on the site, not merely what the plans say.
• Add a margin of safety.

Rule of thumb for margin of safety:

If your order is Order this much extra

1-5 cubic yards .5-1 c.y. extra

6-10 c.y. 1 c.y. extra

11-20 c.y. 1-1.5 c.y. extra

It can be upsetting to end up with any extra concrete. After all, you'll be the one to pay for it. However, you need to understand that ordering just the right amount can help you complete the task as what your client expects.  

Requesting your ready-mix supplier to visit your site

After choosing a Ready-Mix Supplier, have a representative come to your site to give his/her opinion on the quantity required. Compare the figure with what you came up with. Discuss any variances with the supplier.

Your ready-mix supplier is invaluable for checking your view of job conditions. They also play a significant role in checking your margin of safety and identifying underlying issues. Lastly, they can also help you in informing you of any local conditions you need to know.