How many bags of concrete will you really need?
A small patio can turn into a surprisingly tall stack of concrete bags. Before you load the car, let’s work out the amount of concrete, what those bags weigh, and whether ordering ready-mix deserves a look.
The answer is quick. And if you want to know how we got it, there’s an easy printable lesson right below the calculator.
Measure your project
Start with the dimensions from your plan. The defaults are just an example you can change.
Concrete math in three easy steps
Cubic feet ÷ yield per bag = bags needed (round up)
Remember: 27 cubic feet = 1 cubic yard. A 10 × 10 ft slab, 4 inches thick, with a 10% allowance, needs about 1.36 cubic yards of concrete. At QUIKRETE’s approximate 0.60 ft³ yield, that is 62 whole 80-lb bags. Your specific project may need a different thickness or mix.
Concrete bags versus ready-mix: the tradeoff people forget
A bagged mix might be convenient for a small repair. Once the estimate runs into dozens of bags, moving and mixing the material becomes a bigger job. An 80-pound bag isn’t 80 pounds of wet concrete; it’s the weight of the bag you carry before adding water. Your result shows the dry bag total so you can consider loading and handling.
Ready-mix deliveries may be easier on large pours, but many suppliers have minimum order sizes, short-load fees, travel charges and access requirements. Even when you enter both prices above, the estimate compares materials only, not labor, water, tool rental, taxes, delivery, minimum charges or waste handling. Call local suppliers for actual quotes.
Which concrete bag yield should I use?
The QUIKRETE concrete calculator and Sakrete concrete mix specifications both describe approximate yields of 0.30, 0.45 and 0.60 cubic feet for 40, 60 and 80 pound mixes. That’s not a promise for every formulation. Check your actual product’s data sheet and use the adjustable yield input.
What about fence-post holes?
Choose “Round post holes” in the calculator. It uses the volume of a cylinder: π × radius² × depth. The optional post diameter subtracts the space occupied by a round post. Real posts, gaps, irregular excavation and products meant for post setting may change the needed amount.
This tool estimates quantity only. It cannot decide the safe depth, footing diameter, required strength, reinforcement or curing conditions for a structural slab or fence. Follow local code, manufacturer directions and qualified advice for structural or load-bearing work. Contact local utility locating services before digging. Concrete dust and wet cement can harm skin, eyes and lungs; use manufacturer-recommended protection.
Before you load the truck
Double-check the measurements and bag yield. Also think about delivery access, your vehicle’s safe payload, help moving heavy bags, water availability, proper forms, suitable mixing equipment, protective gear and the amount of time available for placing concrete. Working through the shopping list now is easier than discovering a missing tool halfway through a pour.
Helpful tools for a concrete project
Mixing tubs, trowels, finishing floats, protective gloves and measuring tools can be useful. These are optional Amazon search links for supplies, not endorsements of individual products. Bags of concrete or ready-mix are often more practical to purchase locally.
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As an Amazon Associate I earn from qualifying purchases. Check suitability and actual listing prices before ordering. The calculator and printable lesson are free.
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