Concrete Calculator: Yards, Bags & Cost Estimator

A concrete calculator eliminates the guesswork in every concrete pour. Simply enter the dimensions of your slab, footing or column and this concrete calculator will tell you how many cubic yards, bags or ready-mix truck loads you will need.

How to Calculate Concrete For Any Project?

All concrete calculators are based on the same formula: Volume = Length × Width × Depth. When pouring a slab, a sidewalk, or footing, it’s the same procedure in all cases, just filling the volume with a unit that can be purchased.

For those who do not want to do the manual calculation, the concrete calculator on this page will do it for you just enter your shape and dimensions and get cubic yards, bags and estimated cost in one step.

Here’s how to calculate concrete manually, in three steps:

1. Measure the area in feet (length × width).
2. Convert depth to feet a 4-inch slab is 4 ÷ 12 = 0.33 feet.
3. Multiply and divide by 27 to convert cubic feet into cubic yards, since one cubic yard equals 27 cubic feet.

Concrete Yardage Calculator Example

If you are building a 10 x 10 patio that will be 4 inches thick, you can proceed with the calculations. That’s 10 × 10 × 0.33 = 33 cubic feet, or 33 ÷ 27 = 1.24 cubic yards. 

This is exactly what a concrete yard calculator will do automatically; you don’t have to manually convert inches, feet and yards each time.

How Many Bags of Concrete Do I Need?

The basic calculations used for the various brands Quikrete, Sakrete, and others on their own bags are the same, and they usually look like this: an 80-lb bag yields about 0.60 cubic feet of mixed concrete, a 60-lb bag yields about 0.45 cubic feet, and a 40-lb bag yields about 0.30 cubic feet. 

As an example, if you’re using 80 lb concrete mix for a 1.24 yard patio, you will need approximately 56 bags, plus an additional 5–10% for spillage and an uneven subgrade. 

Remember on every bag there is a line stating the yield, and some fast-setting, high-strength mixes may differ slightly. 

Concrete Slab Calculator: Thickness Guide

How thick should a concrete slab be: The most critical value to be determined is the thickness of the slab, so a good concrete calculator, or any concrete slab calculator, would always request the slab’s thickness as a separate value from the surface area. This table is a handy reference guide for a 100 sq. ft. slab. 

Driveways and garage floors typically use 4–6 inch slabs, while footings and structural pads may run thicker depending on local building codes.

Typical Slab Thickness

How Much Does Concrete Weigh?

When you’re considering your delivery access or load limits, a concrete calculator that also provides a weight calculation can come in handy. 

A freshly mixed concrete weighs about 150 pounds per cubic foot, so a cubic yard of concrete will weigh about 4,056 pounds or about 2 tons. 

It is that weight which makes a fully loaded mixer truck a hefty piece of equipment to handle on soft ground or steep driveways.

Which is Cheaper: Ready-Mix Truck Concrete vs. Bagged Concrete?

A concrete calculator set to cost mode commonly known as a concrete slab cost calculator  typically favors ready-mix delivery for projects larger than about a cubic yard, as most concrete mixer trucks in the U.S. have 8, 9 or 10 cubic yards per load, although smaller mini-mix trucks are available for those shoddier spaces.

If your estimator shows you’re close to a full yard, it’s usually worth calling a local ready-mix supplier for a quote before committing to dozens of bags.

Other Common Concrete Calculator Uses

• Footing calculator: for continuous or spot footings under walls and posts.
• Sonotube calculator: for round concrete columns, using the cylinder volume formula (π × radius² × height).
• Cinder block calculator: for block-fill projects, factoring in block cavities.
• Mortar calculator: for the bonding material between blocks or bricks, calculated separately from structural concrete.
• Cement calculator: specifically for the cement-to-aggregate ratio in custom mix designs, rather than pre-mixed bags.

Whether you use a concrete pad calculator, a concrete estimator or a full concrete mix calculator, the math is the same: calculate volume and then convert to the unit you prefer to buy from. 

Frequently Asked Questions

Q1: How many yards of concrete do I need for a 10×10 slab? 

At a standard 4-inch thickness, a 10×10 slab needs about 1.24 cubic yards of concrete. Thicker slabs (5–6 inches) require closer to 1.5–1.85 yards.

Q2: How many bags of concrete are in a yard? 

One cubic yard equals 45 bags of 80-lb mix, 60 bags of 60-lb mix, or 90 bags of 40-lb mix.

Q3: How many yards of concrete are in a truck? 

Most standard ready-mix trucks carry between 8 and 10 cubic yards, though capacities can range up to 11–12 yards for larger mixers.

Q4: How much does concrete weigh per cubic yard? 

A cubic yard of concrete weighs approximately 4,000–4,056 pounds, or about two tons.

Q5: Is it cheaper to buy concrete in bags or order a truck? 

Bagged concrete costs more per cubic yard but works well under one yard. Ready-mix trucks are cheaper per yard but usually have delivery minimums and short-load fees.