How Many Bags of Concrete for a Fence Post?

Knowing how deep your fence post needs to be set is key to answering the question. Learn how to set a post and figure out how much concrete you’ll need.

Price and stock could change after publish date, and we may make money off these affiliate links. Learn more.
February 26, 2021
DIY Wooden Swing Set

Step 3: Place and Secure Frame

Mix two 50lb bags of concrete with water in a mixing tub or 5-gallon bucket. Add concrete into the hole and around the 4” x 4”. Depending on your climate, let concrete set up for 24 - 48 hours.

Photo by: Image courtesy of Brian Patrick Flynn

Image courtesy of Brian Patrick Flynn

The general rule of thumb when setting a post is that the depth of the post’s hole needs to be 1/3 to 1/2 of the actual above-ground height of the post. So, six-foot-high fence posts ideally need to be buried three feet into the ground. The diameter of your post hole should be three times the diameter of your post. So, if you’re planning on using a four-inch round or 4x4-inch square post, your post hole will need to be 12 inches in diameter. For a six-foot-high fence post, we would need a hole that’s 36 inches deep and 12 inches in diameter.

Now that you’ve determined the size of the hole you’ll need, you can use the chart below to determine how many 50-pound bags of concrete you’ll need. Our example post will require two bags for every post if you’re using fast-setting concrete.

Fast-setting concrete is ideal for installing fence posts since it doesn't need to be mixed in a bucket or a wheelbarrow. Once you’ve finished digging your post holes, add about three to four inches of gravel into the bottom and compact it using a post or a 2x4. Then, set your post in place and use a level to ensure that it’s perfectly vertical. Stake your post in place with two braces and pour your dry concrete into the hole, surrounding the post up to about three inches below the lip. Slowly fill the hole in with about a gallon of water, enough so that you’ve saturated all of the concrete.

Fast-setting concrete is generally hardened off in about 20 to 60 minutes, depending on the outside temperature, and is usually cured enough to begin work in about four to six hours. Remember that although you can pour concrete in a wide range of conditions, the safe window for the average homeowner to pour concrete is when the air temperature is between 50 and 90 degrees Fahrenheit. While it’s technically possible to pour in conditions outside of those ranges, it requires a fair amount of experience. Your concrete will cure evenly when temperatures are mild and the water is at a tepid temperature.

Remember, any time you’re planning on digging a deep hole in your yard, it’s a good idea to call your local utilities to come mark your underground wires and pipes. Hitting a gas line or buried power line while digging can be extremely dangerous and even fatal. If you’re curious about what permits you might need for a fence project, you can reach out to your local building inspector’s office or read our handy reference here.

Next Up

How Deep Should I Dig Fence Posts?

Knowing how deep your fence post needs to be is determined by the desired height of your fence. Here’s our breakdown of how to make sure you build a strong fence.

How to Build a Privacy Wall With Fence Panels

Instead of putting up an entire fence, build a unique barrier with freestanding wood panels that will add curb appeal and style.

How To Care For a Wood Fence

A wooden fence can be a great way to give a home a definitive border and add style. Learn the proper maintenance required to make sure your fence lasts a long time.

How to Reinforce Fence Posts

A wobbly fence can be dangerous as well as an eyesore. Follow these instructions to repair leaning fence posts.

How to Build a Fire Pit in an Afternoon

With a short list of materials and just a few hours, you can easily create an inviting fire pit area that will quickly become your new favorite spot in the backyard.

How to Build a Horizontal-Plank Privacy Fence

See how we built a redwood fence on an angle to lend privacy to a sloping backyard.

How to Clean Rust Off Concrete

Follow these directions to remove an unsightly rust stain from your concrete patio, driveway or garage floor.

How to Drill Into Brick or Concrete

Drilling into tough materials can be challenging, but using the proper equipment takes the effort out of anchoring into brick and concrete.

How to Stain or Paint a Wood Fence

Proper maintenance like applying a fresh coat of paint or stain to your fence will help make it last longer and keep it looking great. Follow these tips and instructions to turn your tired, old fence into a backyard statement piece.

How to Make a Garden Fence From Upcycled Pallets

Keep critters out of your garden with this inexpensive fencing alternative that can also serve as a planter.

Go Shopping

Get product recommendations from HGTV editors, plus can’t-miss sales and deals.

On TV

Follow Us Everywhere

Join the party! Don't miss HGTV in your favorite social media feeds.