How to Calculate Cement for Post Holes
Use this post hole volume calculator to accurately figure the amount of concrete required for any sized post hole with or without any common sized post. Returns both cubic yards and how many bags. This free tool is designed as an aid for building fences, barns, post frame buildings, or just anything that has a post in the ground. See instructions below.
- Use the first drop down to select a size for the post. The length makes no difference. To calculate the volume for a footing in the bottom of a post hole, leave the drop down selected “no post”.
- Use inches in the next two number boxes for a diameter and a depth for the post hole. This calculator is only as accurate as the information entered. Make sure to use a tape measure when determining the diameter and the depth for the holes. Check each hole at the top and bottom. Be sure to check these measurements thoroughly and take an average.
- If there is more than one post hole, then change the value from one.
- If bagged concrete will be used then select a size for the bags. They come in 40, 60, and 80 pound sizes.
- See the example video below for more information.
More about Post Holes
If the post holes will be subject to building inspections, then they should be of a size and depth that conforms to the codes in such a document as the 2012 International Residential Code.
The diameter of a post hole should be at least three times as large as the size of the post. The area at the bottom of the hole is where the actual load is transferred to the soil.
The deeper the hole the better. This is especially important for structures such as pole barns and pavilions that do no have exterior wall bracing.
If there is a footing at the bottom of the hole, then it should be at least 6″ thick.
Be certain to dig the hole as flat and level on the bottom as possible. They should also be very close to plumb with the post ending as close to the center as possible.
Never pour in bagged concrete dry. Always premix it to the right consistency. You may as well use no concrete if you are not going to do it right. Remember that bagged concrete is more work than concrete from a truck. It is also more expensive.
To get an accurate lay out for the placement of the holes use batter boards.