Concrete Footing Calculator

Q: What footing type should I pick for a deck post?

Pick Column / Pier . Deck posts sit on round concrete piers that go deep into the ground. Enter the diameter of your tube form and the height of the hole. If your pier has a wider base, turn on the Bell Footing option too.

Q: How does the calculator find the volume of a circular footing?

It uses the formula π × radius² × depth . You enter the diameter, and the calculator divides it by two to get the radius. Then it multiplies by pi and the depth to get the volume in cubic feet.

Updated Jun 12, 2026 By Jehan Wadia

Concrete Volume Required

Total Volume (yd³)

Total Volume (ft³)

Total Volume (m³)

Est. Weight

Pre-Mixed Bags Needed (+10% waste)

40 lb bags (0.30 ft³)0

50 lb bags (0.375 ft³)0

60 lb bags (0.45 ft³)0

80 lb bags (0.60 ft³)0

90 lb bags (0.675 ft³)0

Volume Breakdown

Component	Per Footing (ft³)	Total (ft³)

Bag Count Comparison

Introduction

A concrete footing is the base that holds up a building, wall, or post. It sits below the ground and spreads the weight of the structure into the soil. If the footing is too small or uses too little concrete, the structure can crack, shift, or sink over time. That is why knowing the right amount of concrete matters before you start any pour.

This Concrete Footing Calculator helps you figure out exactly how much concrete you need for your project. It works for four common footing types: continuous (strip) footings, rectangular pad footings, circular pad footings, and column or pier footings. Just enter your dimensions, pick your units, and the tool gives you the total volume in cubic yards, cubic feet, and cubic meters. It also tells you the estimated weight and the number of pre-mixed bags you need, with 10% added for waste.

You can also add a stem wall to strip footings or a bell footing to column piers for a more accurate estimate. Whether you are building a deck, a fence, a retaining wall, or a house foundation, this calculator saves you time, cuts down on waste, and helps you order the right amount of concrete for the job.

How to Use Our Concrete Footing Calculator

Enter the shape, size, and number of your footings below. The calculator will tell you how much concrete you need in cubic yards, cubic feet, and cubic meters, plus how many bags of pre-mixed concrete to buy.

Footing Type: Pick the shape of your footing. Choose Continuous/Strip for long wall footings, Rectangular Pad for square or rectangle pads, Circular Pad for round pads, or Column/Pier for round posts that go into the ground.

Length: Enter the total length of your footing. This field shows for Strip and Rectangular Pad types. Pick your unit from the dropdown — inches, feet, yards, centimeters, or meters.

Width: Enter how wide your footing is. This field shows for Strip and Rectangular Pad types. Pick your unit from the dropdown.

Depth: Enter how deep or thick your footing is. This field shows for Strip, Rectangular Pad, and Circular Pad types. Pick your unit from the dropdown.

Diameter: Enter the width across your round footing or column. This field shows for Circular Pad and Column/Pier types. Pick your unit from the dropdown.

Height: Enter how tall your column or pier is from top to bottom. This field only shows for the Column/Pier type. Pick your unit from the dropdown.

Number of Footings: Enter how many identical footings you need to pour. The calculator multiplies the volume of one footing by this number.

Add Stem Wall: Turn this on if your strip footing has a stem wall on top. Enter the wall thickness and wall height. The stem wall volume is added to the base footing volume.

Add Bell Footing: Turn this on if your column pier has a flared bell at the bottom. Enter the bell diameter and bell height. The bell volume is added to the shaft volume.

Calculate: Press this button to get your results. The calculator shows total concrete volume, estimated weight, bags needed with 10 percent extra for waste, a volume breakdown table, and a bar chart comparing bag sizes.

Reset: Press this button to clear all fields and start over with the default values.

What Is a Concrete Footing?

A concrete footing is the base that sits under a wall, column, or pier and spreads the weight of a structure into the ground. Footings stop buildings from sinking, shifting, or cracking. They are one of the first things poured when construction begins.

Types of Concrete Footings

There are several common footing types used in construction. A continuous or strip footing runs along the length of a wall and is the most common type for houses and small buildings. A rectangular pad footing is a flat slab that supports a single post or column. A circular pad footing works the same way but uses a round shape. A column or pier footing is a tall cylinder of concrete that goes deep into the ground, often used for decks, porches, and fences. Some pier footings include a bell at the bottom, which is a wider cone shape that gives extra support in soft soil. If you are working with cylindrical pier forms, our Sonotube Calculator can help you estimate the concrete needed for round tube forms specifically.

How This Calculator Works

This calculator finds the total volume of concrete you need for your footings. You pick your footing type, enter the dimensions, and choose how many footings you need. It gives you the volume in cubic yards, cubic feet, and cubic meters. It also shows the estimated weight and tells you how many pre-mixed bags to buy. The bag count includes an extra 10% for waste, which is normal on any concrete job. For general concrete pours such as driveways, patios, and walkways, you can also use our Concrete Calculator. If you are pouring a flat slab rather than a footing, the Concrete Slab Calculator is designed specifically for that. And if you are working with a specific brand of pre-mixed bags, our Quikrete Calculator can give you a quick bag count estimate.

Why Footing Size Matters

Footings must be the right size to hold the load above them. If a footing is too small or too shallow, the structure can settle unevenly and crack. Most local building codes set minimum footing sizes based on soil type and the weight the footing must carry. In cold climates, footings must also reach below the frost line so freezing soil does not push them upward. Always check your local building codes or talk to an engineer before you pour. Knowing the square footage of your project area can help you plan your footing layout and spacing.

Tips for Pouring Concrete Footings

Compact the soil at the bottom of your trench before you pour. If you need to calculate how much soil to remove, our Excavation Calculator can help with the dig.
Use forms made of wood or metal to hold the concrete in shape.
Add rebar or wire mesh if your building code requires it.
Pour all the concrete for one footing at the same time so it bonds as one piece.
Let the concrete cure for at least 48 hours before building on top of it.
Order a little more concrete than the exact amount — spills, uneven ground, and form bulges always use extra material. You can check the Concrete Weight Calculator to estimate the total weight of your pour for delivery planning.
If you are building a block wall on top of your footing, use the Concrete Block Calculator to figure out how many blocks you need. For the mortar between those blocks, the Mortar Calculator will give you an accurate estimate.

Frequently asked questions

What footing type should I pick for a deck post?

Pick Column / Pier. Deck posts sit on round concrete piers that go deep into the ground. Enter the diameter of your tube form and the height of the hole. If your pier has a wider base, turn on the Bell Footing option too.

What does the 10% waste factor cover?

The 10% extra covers concrete that spills, sticks to tools, fills uneven ground, or gets lost when forms bulge. Most concrete jobs waste between 5% and 10%, so this keeps you from running short.

Can I mix different units like inches and feet in the same calculation?

Yes. Each field has its own unit dropdown. You can enter width in inches, length in feet, and depth in centimeters if you want. The calculator converts everything for you automatically.

What is a stem wall and when do I need one?

A stem wall is a short concrete wall that sits on top of a strip footing. It raises the structure above ground level. You need one when building a house foundation or retaining wall that must extend above the footing. Turn on the Add Stem Wall toggle to include it in your total.

What is a bell footing on a column pier?

A bell footing is a wider, cone-shaped base at the bottom of a pier. It spreads the load over more soil. You use it in soft or loose soil where a straight pier would not have enough support. Turn on the Add Bell Footing toggle and enter the bell diameter and height.

How do I know which bag size to buy?

The calculator shows how many bags you need for each size: 40, 50, 60, 80, and 90 pounds. Bigger bags cost less per cubic foot but are heavier to carry. Pick the size you can lift comfortably. For large jobs, ordering ready-mix by the cubic yard is usually cheaper.

When should I order ready-mix concrete instead of bags?

If your total volume is more than 1 cubic yard, ready-mix from a truck is usually faster and cheaper. Mixing more than about 45 bags of 80-pound concrete by hand takes a long time and a lot of effort.

How deep should my footing be?

Most building codes require footings to be at least 12 inches deep. In cold climates, footings must go below the frost line, which can be 36 inches or more. Check your local building code for the exact depth required in your area.

How does the calculator find the volume of a circular footing?

It uses the formula π × radius² × depth. You enter the diameter, and the calculator divides it by two to get the radius. Then it multiplies by pi and the depth to get the volume in cubic feet.

How is the estimated weight calculated?

The calculator multiplies the total volume in cubic feet by 150 pounds, which is the standard weight of cured concrete per cubic foot. If the total is 2,000 pounds or more, the result shows in tons instead.

What is the difference between a strip footing and a rectangular pad footing?

A strip footing is long and runs under an entire wall. A rectangular pad footing is a shorter slab that supports a single post or column. The math is the same — length times width times depth — but they serve different purposes.

Can I calculate multiple footings at once?

Yes. Enter the number of identical footings in the Number of Footings field. The calculator multiplies the volume of one footing by that number to give you the total concrete needed.

Do I need rebar in my footing?

Most building codes require rebar in footings that support structures. Rebar keeps the concrete from cracking under load. Check your local code to find out the size and spacing of rebar you need.

What if my footings are different sizes?

Run the calculator once for each size. Write down the volume for each group, then add them together by hand to get your total concrete needed.

How accurate is this calculator?

It gives a close estimate based on the dimensions you enter. Real-world factors like uneven trench walls, sloped ground, and form movement can change the actual amount. That is why the bag count includes 10% extra for waste.