Tips to Calculate Enough Concrete to Order from Concrete Suppliers
Now that warmer weather is here, it’s a good time to start planning concrete projects around the home. Maybe you want a new concrete slab for a shed or a backyard patio. Or, maybe you want to redo your garage floor and driveway.
Whatever the project, it’s important that you order enough concrete to get the job done in one pour. The last thing you want when placing concrete is to run out mid-way through.
Concrete slabs placed in one pour are much stronger and will last longer than concrete poured at separate times.
To avoid running out of concrete in the middle of your project, you’ll need to measure the right amount before ordering from your concrete supplier.
Even with a concrete calculator, you need to take a few things into account when measuring the right amount of concrete to pour. And in some cases, you might need to make some measurements on the fly.
To help you order the right amount of concrete for your project, we’ve compiled a few helpful measurement and calculation tips.
Tools You’ll Need
- Tape measure
- Notepad and pencil
- Calculator
Calculating the Amount Of Concrete
Take Measurements
Using the tape measure, measure the area where you plan to place the concrete, writing down the following measurements:
- The length (L);
- The width (W); and,
- The height (H), also referred to as the depth (D).
Use a Concrete Calculator
Concrete calculators are available online from concrete suppliers. Simply input your measurements, whether in millimetres, centimetres, metres, inches, feet, or yards. The calculator will do the work for you to find the volume of concrete you’ll need for your project.
Calculating Cubic Metres
If you took metric measurements, then multiply the length by the width by the depth (L x W x D) to find the volume needed in cubic metres. For measurements in centimetres, multiple the measurements by 100 to find the amount in metres.
Here’s an example of how to calculate area in cubic metres:
15.2 m (L) x 4.6 m (W) x 0.1 m (D) = 6.992 cubic metres
Calculating Cubic Feet
To calculate cubic feet or cubic yards, you first need to convert your measurements in inches to Engineer’s Scale.
Engineer’s Scale takes one foot (12 inches) and converts it into tenths. This scale also eliminates fractions of an inch, converting fractions into decimals (i.e. ½ to 0.5, or ¾ to 0.75).
To illustrate this conversion, the following measurements will be used as an example:
L = 12 feet, 6 inches;
W = 15 feet;
H (D) = 3 and ¾ inches.
Since you only need to convert the inches to feet, any measurement in feet will remain the same.
Converting Length (L) of 12 feet, 6 inches to feet:
- Take the 6 inches and divide by 12 (since there are 12 inches in one foot).
- 6 inches / 12 = 0.50 feet
- Replace inches with feet in the measurement to get the new measurement of L = 12.5 feet.
- Since the W measurement is only in feet (15 feet), you do not need to convert this. So W = 15 feet.
Converting Height (H) or Depth (D) of 3 and ¾ inches to feet:
- First convert the fraction (3/4) to a decimal. Divide 3 by 4.
- 3 / 4 = 0.75 of an inch
- This results in 3.75 inches.
- Next, divide 3.75 inches by 12.
- 3.75 / 12 = 0.31 feet
- H (D) = 0.31 feet
To measure the cubic feet, multiply the three converted measurements together (L x W x H).
12.5 feet x 15 feet x 0.31 feet = 58.25 cubic feet
Calculating Cubic Yards
To calculate the measurement into cubic yards, take the total cubic feet and divide by 27 (which is the number of cubic feet in a cubic yard).
58.25 cubic feet / 27 = 2.15 cubic yards
Safe Rules of Thumb For Ordering Concrete
When ordering concrete from your local concrete supplier, keep these rules of thumb in mind to ensure you order enough concrete and the right mix for your project needs.
Add 10%
Once you’ve calculated the amount of concrete needed to fill an area, add 10 percent to that amount to account for spillage and possible variations in slab depth.
Multiply the number by 0.10, then add this value to your total amount.
For example: 2.15 cubic yards x 0.10 = 0.215
0.215 + 2.15 cubic yards = 2.365 cubic yards
Concrete Strength
Concrete mixes come in various strengths for various uses. For example, a concrete driveway will require more strength than a shed since it will be holding the weight load of vehicles. The strength of concrete is measured in pounds per square inch (psi).
So when you order concrete from your concrete supplier, make sure to tell them what the concrete is being used for. Depending on your project needs, they will recommend a specific strength of concrete mix. And if you live in Ottawa, or any other temperate location with a freeze/thaw cycle, your concrete supplier will also suggest a specific percentage (i.e. 5%) of air-entrained concrete to withstand the fluctuating temperatures without being damaged.
Keep these measurement, calculation, and ordering tips in mind so you can pour the right amount of quality concrete during your home projects this summer.
