Concrete & Masonry Calculators
Work out how much concrete to buy before you mix a single bag. These calculators handle the shapes people actually pour at home — slabs, post holes, footings, tube-form columns, steps and round pads — and convert the volume into bags or a ready-mix order. For a paver patio or walkway, count the pavers together with the compacted base and bedding sand under them, and for a blacktop driveway, convert area and thickness into tons of hot mix.
- Concrete Bag CalculatorHow many bags of concrete do you need? Calculate 40, 50, 60 or 80 lb bags for a slab, post holes or fence posts, with waste and gravel base built in.Open calculator
- Concrete CalculatorAdd slabs, footings, round columns (tube forms), steps, walls and round pads in one list and get total cubic yards, a ready-mix order and bag counts.Open calculator
- Paver CalculatorCalculate pavers for a patio or walkway with cut waste, plus paver base gravel in tons and cubic yards, bedding sand and bags of polymeric joint sand.Open calculator
- Asphalt CalculatorHow many tons of asphalt do you need? Turn driveway or patch area and compacted thickness into tons of hot mix, with base stone, waste and a cost estimate.Open calculator
Bags or ready-mix?
The tipping point is about one cubic yard — 45 bags of 80 lb mix. Below that, bags are usually cheaper and a single person can mix them in a wheelbarrow or small mixer. Above it, price a ready-mix delivery (and ask about short-load fees), or rent a towable mixer. The bag calculator shows the count for every bag size so you can compare.
Getting the volume right
Most concrete shortfalls come from the base, not the math: a subgrade that’s half an inch low across a patio adds several percent of volume. Check depths with a string line before ordering, and add 5–10% for waste. For projects with several shapes — a slab plus piers or steps — the multi-shape concrete calculator adds them into one order.
Before you pour
- Call 811 before digging post holes or footings — it’s free and required in most states.
- Footing depth, size and reinforcement are set by local code and soil conditions; your building department can tell you what applies.
- Plan a compacted gravel base under slabs; the gravel calculator gives tons and yards.
Quick conversions
One cubic yard is 27 cubic feet. Using the yields printed on a major brand’s data sheet — about 0.60 cu ft for an 80 lb bag, 0.45 for 60 lb and 0.30 for 40 lb — one yard takes roughly 45 bags of 80 lb, 60 bags of 60 lb or 90 bags of 40 lb. That is about 3,600 lb of dry mix per yard, which matters if you plan to haul it yourself: check the payload rating of your truck or trailer before you load it.
| Bag size | Yield per bag | Bags per cubic yard |
|---|---|---|
| 40 lb | 0.30 cu ft | 90 |
| 60 lb | 0.45 cu ft | 60 |
| 80 lb | 0.60 cu ft | 45 |
A worked example
A 10 × 10 ft patio slab 4 in thick is 10 × 10 × 4 ÷ 12 = 33.3 cu ft, or 1.23 cubic yards. That is 56 bags of 80 lb mix before waste; with a 10% allowance it becomes 62 bags. At that size, compare the bag price against a short-load ready-mix delivery, and think about how many people you will have to mix and place 62 bags before the first ones start to set.
Choosing a mix and water
General-purpose concrete mixes are made for pours about 2 in thick or more — slabs, footings, steps and post holes. For thinner toppings or repairs, use a product made for that thickness. Add water as the bag directs: one widely sold 80 lb mix calls for roughly 6 pints to start and about 6–9 pints in total. Extra water makes the mix easier to place but weaker, so add it a little at a time.
Asphalt driveways: tons of hot mix
Asphalt is the other common driveway surface, and it is bought by weight rather than by the yard. Multiply the area by the compacted thickness to get cubic feet, then multiply by the weight of compacted mix: typically 144–160 lb per cubic foot, or about 110 lb per square yard per inch in highway estimates. A 50 × 12 ft driveway at 3 in is 150 cu ft, about 11 tons. The asphalt calculator does this, adds the crushed-stone base under a new driveway and gives a cost line if you enter the price per ton.
Pavers: units, base and sand
A paver patio is masonry laid on a compacted base instead of poured concrete. The pavers are counted by face size: 144 ÷ (length × width in inches) per square foot, plus extra for cuts. The hidden work is underneath. ICPI recommends at least 4 in of compacted crushed-stone base for patios and walks, 6 in for residential driveways, and 1 in of concrete sand as the bedding layer. The paver calculator turns those depths into tons of base, loose yards to order, bedding sand and bags of polymeric joint sand.
Each calculator lists its sources at the bottom of the page, including the manufacturer data sheet behind these yields.
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