# Concrete Calculator for Estimating Yards&Bags for a Slab&Footing

When you want to develop a building construction project, you definitely need to use concrete. The truth is that you can choose between buying pre-mixed bags or you can get the concrete you need measured in cubic yards. So, one of the easiest ways that you have to know how much concrete you need for your building construction project is to use a concrete bag calculator in case you want to buy pre-mixed bags of concrete or a concrete yards calculator, when you want to make the mix by yourself.

No matter what option you choose, it’s very important that you understand how these quantities are achieved. The truth is that you may need to make some adjustments to the quantities that you order and the only way to do this right is by knowing how you can estimate the concrete you need without using a concrete bag calculator or a concrete yards calculator.

## #1: Estimating How Much Concrete You Need

In order to know how much concrete you need for your building construction project, you first need to determine the shape it will have. The truth is that the formulas to calculate the concrete you need will be different depending on the shape of your project. While if you intend to do a building construction that is rectangular you will need to multiply the width by the length, and by the height (all in yards), the formula used will be completely different if your building construction project features a circle or is a column, for example.

One of the things that you need to pay attention to no matter if you’re using a concrete bag calculator, a concrete yards calculator, or doing your calculations by hand, is that you need to convert all measurements into yards. Even if you’re using a different unit to know the dimension of your building construction project, you will need to convert it into yards.

## #2: Using a Concrete Calculator

In case you decide to use a concrete bag calculator or a concrete yards calculator, you will need to insert some specific values related to your building project. You will need to know if the calculator that you decide to use uses imperial or metric measurements so that you get the right values for the amount of concrete that you need to buy.

In case the calculator you decide to use only uses the imperial system, you will need to enter your project dimensions in yards, feet, or inches. In case the calculator only uses the metric system, you will need to use your project dimensions in meters or centimeters.

As a result, the calculator should provide you with the number of bags that you will need for your project. Most of the concrete bag calculators that you find will include the number of bags of concrete of 40 pounds, 60 pounds and 80 pounds bags of concrete.

## #3: Determine How Much Concrete You Need Without A Concrete Bag Calculator Or A Concrete Yards Calculator:

In order to determine the quantity of concrete that you need for your construction project, you will need to make several calculations. All you need to do is to follow the next steps:

**Step #1:**The first step is to measure the area of your building project. You need to measure the length, the width, and the height of the slab, footing, or column. However, not all building projects are straight and you may have some problems determining the area. So, the best thing you can do is to divide your building project into smaller areas and determine each area on its own. Then, you just need to add all the cubic yards together.**Step #2:**Now that you already know the dimensions of your building project in cubic yards, you will need to convert it into feet. So, knowing that 1 yard is equal to 3 feet, if your building project has 21 yards, this is the same as 63 (21*3).**Step #3:**Now, you will need to find the cubic yardage of your space. In order to determine this value, you just need to multiply the width by the length by the height.**Step #4:**You will now need to convert the volume from cubic feet to cubic yardage. In order to do it, you just need to divide the cubic footage that you got by 27.**Step #5:**Since most concrete sellers won’t have fractions of a yard of concrete available, you will need to round the result to the nearest yard up.**Step #6:**In case your building project is small, you may prefer to use pre-mixed bags. We will see the reasons below. However, for now, you need to know that when you choose to use pre-mixed bags of concrete, you will have at your disposal different bag sizes. To give you a better idea of what you can expect to find:- It takes 90 40lb bags of concrete to fill 1 cubic yard of volume.
- It takes 60 60lb bags of concrete to fill 1 cubic yard of volume.
- It takes 45 80lb bags of concrete to fill 1 cubic yard of volume.

**Step #7:**Now, it’s finally the time to order the concrete for your building project. As a rule of thumb, you should always order between 5 and 10% more material than the one that you got from the calculations. The truth is that many things can happen where you waste concrete. These include spillage, setting, and overall waste.

**Here are some of the formulas that you can use for calculating the cubic yards of your building project:**

**1. Square and Rectangular Areas**

volume = width × length × height

yds3 = width yds × length yds × height yds

yds3 = (width ft × length ft × height ft) / 27

**2. Circular and Cylindrical Areas**

volume = π × radius2 × height

yds3 = π × radius yds × radius yds × height yds

yds3 = (π × radius ft × radius ft × height ft) / 27

π = 3.14159265359

**3. Steps**

In order to calculate the cubic yards of steps, you will need to divide them into rectangles first. Then, you will need to find the volume of each step or rectangle that you have. In the end, you will need to sum all the rectangles or steps of your project.

volume = width × length × height

yds3 = width yds × length yds × height yds

**4. Cube**

cube volume = e3

e = edge length

**5. Rectangular Prism**

prism volume = l X w X h

l = length

w = width

h = height

**6. Sphere**

sphere volume = 4/3 X π X r3

r = radius

**7. Cylinder**

cylinder volume = π X r2 X h

r = radius

h = height

**8. Cone**

cone volume = 1/3 X π X r2 X h

r = radius

h = height

**9. Pyramid**

pyramid volume = 1/3 X e2 X h

e = edge length

h = height

**10. Capsule**

capsule volume = π X r2 x h + 4/3 X π X r3

r = radius

h = height

**11. Cap**

cap volume = π/6 X h(3 X r2 + h2)

r = radius

h = height

## #3: What Should You Choose: Order Concrete By The Yard Or Pre-Mixed Bags?

The answer to this question depends on your building project.

The truth is that if you have a large building project such as building a driveway, you should opt for ordering concrete by the yard instead of buying pre-mixed bags. On the other hand, when you have a small building project such as a small patio, footings or a walkway, you should prefer the pre-mixed bags instead.

Pre-mixed bags of concrete should be ordered when you want to be:

- setting posts for mailboxes or fences
- pouring small slabs for patios or sidewalks
- pouring small ramps, steps, or curbs
- making repairs to steps, walkways, or walls
- footings for walls, pergolas, decks, and others.

In case this is your option, you need to know that in case you order a small number of bags, you may need to pick them out by yourself. In addition, you need to also be aware that you will need the right equipment for mixing the concrete. While a renter mixer can be helpful the truth is that a wheelbarrow will only work for a few bags.

Concrete by the yard should be ordered when you want to build:

- commercial sidewalks or parking lots
- foundation slabs for a house
- pool decks, driveways, large patios, among others.

## #4: Estimating the Cost to Install Concrete Slab

The truth is that most of us don’t have the slightest idea about how much it costs to install a concrete slab. However, it is important to know in order to evaluate if you should be the one doing the construction project or if it will be more affordable just to hire someone to do the job for you.

Installing a concrete slab costs, on average, between $6 and $16 per square foot. However, these aren’t the only costs that you will have. The truth is that you need to add the cost of the concrete itself as well as all the labor costs that will include the preparation of the area, the pouring, and also the finish. And speaking about the finish, when you are looking for a more affordable solution, this will only include a standard brush finish. However, if you intend to have a decorative finish with some coloring, this will cost you more.

If you have decided to do things on your own, there are some tips that you need to know about the preparation of the area.

**Preparing to Pour Concrete:**

The truth is that most of the job of pouring concrete needs to be done before the truck arrives at the area where you are building your project.

You will need to ensure that you have the site measured and laid out as well as you need to have all the forms that will contain the footing or the slab properly installed.

You should also make sure that the rebar is açready in place to ensure that it reinforces the concrete and prevents it from cracking in the near future.

**Tips For Ordering Concrete**

- Before you order the concrete for your building project, you need to know that there are different kinds of mixes. So, calling your supplier and letting him know more about your project and about the area where you are can help you get the best concrete.
- In case you are planning to buy concrete by the yard, you need to make sure that you are aware of all the costs involved with its transportation. The truth is that you will need to pay some fees regarding the transportation, weekend service, delivery, overtime for long unloading times, and small loads.
- Make sure that you always order 10% more of concrete. The truth is that there will always be some waste either by spillings, settlings, among others. So, by ordering more, you’ll be preventing having a bad pour that can reflect later in seeing your concrete crack.
- As a rule of thumb, you should always add about 1/4” to the thickness of your slab. While this doesn’t seem a lot, it will be more than enough to endure that you have the job evenly grade at the right depth, as well as you can rest assured that the grade will be well compacted.
- When it is time to check the grade and you see that it isn’t the same of different spots, you want to make sure that you fix it.
- Not all building projects are the same as well as not all building projects have regular forms. So, the best thing you can do to ensure that you have the right measurements is to convert them all into rectangles. This will help you determine the area easily.

**Calculating the amount of concrete needed for footings**

The truth is that it isn’t easy to deal or work with footings. Why? They will almost never follow the drawing exactly. For example, if you are working on a rocky soil, the footings may suddenly collapse when you are excavating big rocks. Many different situations can lead to this. It may have rained a lot or the excavator simply dug too deep. Nevertheless, the most important thing that you need to do is to check different spots on your footing and see the average size.

## #5: Using Bags of Concrete

As we have already mentioned, when you have a smaller building project, you should consider using bags of pre-mixed concrete. So, if this is your case, you need to know that you have three different sizes of bags available: 40 pounds, 60 pounds, and 80 pounds.

However, if you have a large slab or just have too many footings, it may be hard to mix bags on-site. So, when you don’t need a lot of concrete, these pre-mixed concrete bags are ideal.

## #6: Estimating Concrete Steps

One of the building projects that most people tend to have more difficulties with is steps. The truth is that steps seem more complicated than they really are.

Here are the 3 simple steps you need to follow when you want to build your own concrete steps:

**Step #1:** Determine the concrete that you need for the porch.

**Step #2:** Calculate the sides of the porch as well as the steps.

**Step #3:** Calculate the amount that you need of base fill.