Frequently Asked Questions
Your common questions about concrete calculation, materials, and projects, answered.
How accurate is this concrete calculator?
Our calculator uses standard industry formulas for volume and material estimation. The results are highly accurate for typical rectangular and cylindrical shapes. However, always add a 5-10% waste factor to account for spillage, uneven ground, and formwork variations.
What do the concrete grades (C15, C20, C25) mean?
The 'C' stands for Compressive strength, and the number represents the strength in megapascals (MPa) after 28 days. For example, C25 has a characteristic compressive strength of 25 MPa, which is approximately 3625 psi. Higher numbers mean stronger concrete, suitable for more demanding structural applications.
Can I use this for both ready-mix and hand-mixing?
Yes. The calculator provides the total volume needed, which you can order from a ready-mix supplier. It also provides a material breakdown (cement, sand, gravel) for those who prefer to mix it themselves. For smaller jobs, you can use our Concrete Bag Calculator to determine the number of pre-mixed bags required.
What is the difference between cement and concrete?
Cement is a key ingredient in concrete, but it's not the same thing. Concrete is a composite material made of three main components: aggregate (sand and gravel), cement, and water. The cement acts as a binding agent that hardens and holds the aggregate together.
How long does concrete take to cure?
Concrete sets and becomes hard enough to walk on within 24 to 48 hours. However, it continues to gain strength for weeks. It reaches about 70% of its final strength in the first week and is considered fully cured after 28 days.
How much does a yard of concrete weigh?
A cubic yard of standard concrete weighs approximately 4,050 pounds (or about 2 tons). This can vary slightly depending on the mix design and the type of aggregate used.