Annuity Payout Calculator
The income a lump sum can pay, and for how long.
Concrete Calculator
Concrete volume for slabs, footings, columns and steps.
Bagged mix
Bags are only economical for small pours — beyond about a cubic yard, ready-mix costs less and saves a great deal of work.
| Bag size | Yield each | Bags needed |
|---|
Typical slab thicknesses
| Use | Thickness |
|---|---|
| Garden path or shed base | 3–4 in (75–100 mm) |
| Patio | 4 in (100 mm) |
| Driveway, cars only | 4–5 in (100–125 mm) |
| Driveway, heavy vehicles | 6 in (150 mm) |
| Garage floor | 5–6 in (125–150 mm) |
Concrete to order
—
Volume
Exact volume—
With waste—
Cubic metres—
Cubic feet—
—
Estimated cost at your rate
Ordering the exact calculated volume reliably leaves you short — sub-base is never perfectly level and forms bow under load. Five to ten percent over is far cheaper than a second delivery, and running out mid-pour creates a cold joint through the slab.
Quick Tool Overview
The Concrete Calculator works out pour volume for slabs, footings, columns, walls, steps and curbs, converts it into cubic yards, cubic metres and bag counts, and applies a waste allowance so the number you order is the number you actually need.
- What it does
- Calculates concrete volume and the quantity to order
- You give it
- A shape, its dimensions and a waste allowance
- You get back
- Cubic yards, cubic metres, bag counts and cost
- Best for
- Slabs, footings, post holes and small pours
About the Concrete Calculator
Work out how much concrete a pour needs, for slabs, footings, square or round columns, walls, steps and curbs. The result is given in cubic yards and cubic metres, converted into bag counts for the common bag sizes, and priced if you supply a rate.
A waste allowance is applied by default, and it matters more than people expect. Sub-base is never perfectly level, forms bow slightly under load, and a little always ends up on the ground, so ordering the exact calculated volume reliably leaves you short. Five to ten percent is the usual margin, and being marginally over is far cheaper than a second delivery or a cold joint through the middle of a slab.
Key features of the Concrete Calculator
Seven pour shapes
Slab, footing, round and square column, wall, steps and curb, each with the dimensions it actually needs.
Waste allowance built in
Five to ten percent, because uneven sub-base and bowing forms mean an exact order routinely comes up short.
Bag counts for every size
40, 60 and 80 lb bags, with a note on where ready-mix becomes the cheaper option.
Imperial and metric
Feet and inches or metres, with cubic yards and cubic metres both reported.
Cost estimate
Enter a rate per yard or per bag and the total is priced.
How to use the Concrete Calculator
-
1
Pick the shape
Slab, footing, round or square column, wall, steps or curb.
-
2
Enter the dimensions
In feet and inches or in metres — thickness is usually the value people get wrong.
-
3
Set a waste allowance
Five to ten percent is standard. It covers uneven sub-base and spillage.
-
4
Read the order quantity
Cubic yards, cubic metres, bag counts and an optional cost.
Frequently asked questions
Multiply length by width by thickness, keeping units consistent, then convert to cubic yards by dividing cubic feet by 27. A 10 × 10 foot slab at 4 inches thick needs about 1.23 cubic yards.
About 45 bags of 80 lb, 60 bags of 60 lb or 90 bags of 40 lb. Bagged mix is only economical for small pours — beyond roughly a cubic yard, ready-mix is cheaper and far less work.
Five to ten percent. Sub-base is never perfectly level and forms bow under load, so an exact order routinely comes up short — and running out mid-pour creates a cold joint.
Four inches is typical for a patio or shed base, five to six inches for a driveway carrying vehicles. Local building codes take precedence over any rule of thumb.
Reviews of the Concrete Calculator
What people who use the Concrete Calculator think of it. Reviews come from visitors and are posted as written.
No ratings yet
Yours would be the first.
- 5 0 reviews rated 5 stars
- 4 0 reviews rated 4 stars
- 3 0 reviews rated 3 stars
- 2 0 reviews rated 2 stars
- 1 0 reviews rated 1 star
0 reviews
Newest first
No reviews yet
Be the first to rate the Concrete Calculator. It takes half a minute and no account.
Write the first reviewMore calculators
Confidence Interval Calculator
Intervals for a mean or a proportion, with the margin of error.
Heat Index Calculator
Apparent temperature from heat and humidity, with risk levels.
Right Triangle Calculator
Solve a right triangle from any two known values.
Love Calculator
A light-hearted compatibility score from two names.
Geometry Calculator
Area, perimeter, surface area and volume for every common shape.
Currency Calculator
Convert between currencies using a rate you set, with fees included.
Roman Numeral Calculator
Convert to and from Roman numerals and do arithmetic in them.