Calculate how plenty of yards or how countless bags of concrete you’ll require for a set of short article holes by start the write-up diameter and hole size.

You are watching: How many 80lb bags of concrete per fence post

If you not sure what dimension hole to dig, a preeminence of ignorance is to use a hole diameter 3 times the post diameter and also 1⁄3 together deep together the post height. See below for an ext information.

average is $115 every yd3, although your price will certainly vary based on the kind of concrete, vendor, and also location.
Use the write-up hole estimator come quickly uncover out exactly how much concrete friend will need to set your fence posts. Enter your post and also hole dimensions in any units.

The calculator will provide you the results in cubic yards and also the variety of pre-mixed bags the concrete (40 lb, 60 lb, and 80 lb bags).

To ensure that your write-ups are sturdy for a long time to come, remember to make her holes 3 times the diameter of her post and 1⁄3 together deep together your fence. So, a 6’ high fence requirements holes a minimum the 2’ deep.

Order extr material come account because that settling and also spillage. If you have many posts to set, it may pay you come mix the concrete yourself. Or, if you require a cubic garden or more, bespeak mixed and delivered.

Concrete contractors can administer estimates for delivering and installing cement because that your short article project.

Illustration mirroring a post hole through a diameter the is 3 times the post’s diameter and also with a depth the is 1/3 the elevation of the post.

How to discover the amount of Concrete Needed

Concrete is offered pre-made (and typically delivered) by the cubic garden or in pre-mixed bags by weight.

To calculate just how much concrete you need, you require to know the write-up size you space going come use and also how many write-ups you room installing. Your short article diameter and also height identify how huge each hole requirements to be.

As declared above, fence article holes must be three times the diameter of your post and also 1⁄3 as deep together your post.

First, you need to calculate the volume because that the short article hole. Then calculation the volume for the component of the short article that will be submerged in the hole. Make certain all your units space the same!

To easily use the table above, transform your systems to feet if they no already. Use our calculators to quickly transform convert inches, yards, or meter to feet.

Post feet Volume Formulas

Use this formulas to calculation volume or, for round holes, use our cylinder cubic yardage calculator.

Rectangle: volume = size x width x depthCylinder: volume = radius2 x π x depth (π = 3.14)

Calculate Concrete Volume

With the volume the the submerged post and also the volume of the feet figured out, subtract the article volume from the feet volume, and also you will have the volume of concrete required for every hole. Simply multiply that amount time the variety of posts to gain a full quantity. Nothing forget to add in part extra for spillage and also waste.

If you have actually multiple various size short article holes come fill, calculation each set with corresponding dimensions separately, then add the totals together.

Example Fence article Concrete Calculation

Let’s use an instance to highlight what we spanned above. Let’s say we space installing a 6’ fence. Therefore, 2’ of the write-up will be in the ground. You require twenty (20) 4” nominal round posts. Keep in mind that 4” articles are actually 3 ½” in diameter. Use the formulas over for volume.

Calculate the post volume

Change article diameter come feet:

3.5” / 12 = 0.2917’

Find radius (½ that the diameter):

0.2917’ / 2 = 0.1458’

Volume of ring post:

(0.1458’)2 x π x 2’ = 0.1336 cubic ft.

Calculate the feet volume

Hole radius (3x short article radius):

3 x 0.1458’ = 0.4374’

Volume of post hole:

( 0.4374’)2 x π x 2’ = 1.2026 cubic ft.

Calculate concrete volume

Hole volume – write-up volume:

1.2026 – 0.1336 = 1.069 cubic ft. Every post

TOTAL volume concrete:

1.069 cubic ft x 20 short articles = 21.38 cubic ft.

Convert to cubic yards:

21.38 cubic ft. / 27 = 0.79 cubic yards

Hint: friend can also use a concrete calculator for this step.

You might find it simpler to convert the cubic footage to cubic yards; if so, divide the cubic clip by 27.

Most concrete service providers will not sell fractions the a garden of concrete, despite it is worth questioning about. So, in this example, friend would want to buy bags. Making use of the table below, girlfriend would have to buy at the very least eight 80 lb. Bags and one 40 lb. Bag (yielding a complete of 5.1 cubic feet) that concrete to enable enough for extra.


Pre-Mix Bag Concrete Yield

The following table mirrors the approximate yield of combined concrete for usual bag weights.

Approximate yield for various bags the concreteBag Concrete WeightMixed Concrete yield (approximate)
40 lb (18.1 kg)0.30 cu ft (8.5 L)
60 lb (27.2 kg)0.45 cu ft (12.7 L)
80 lb (36.3 kg)0.60 cu ft (17 L)

Tips because that Ordering Concrete

Consider these tips to ensure your concrete installation go smoothly.

Type the concrete and also its ideal installation

This relies on the application and the climate where you live. Cooler temperatures need much longer curing times; sandy soils need various shaped holes; an ext extreme freeze/thaw cycles need greater strength concrete than much more temperate regions.

Your concrete supplier can advise girlfriend on the ideal mix to use for your project and region.

Additional costs

For ready-mix concrete delivery, there are typically additional fees because that delivery, weekend service, little loads, and overtime for lengthy unloading times. Comment on these concerns with her concrete supplier ahead of time so the you have actually a clear understanding of costs and also can setup accordingly.

Additional concrete

Order extra concrete (overage) for your project. The amount of overage you setup for will vary based upon your quantity, but setup for at the very least 10% overage come accommodate spillage, settling, and grading inconsistencies.

This will conserve you from a poor pour (concrete installed in parts bring about a separated, weak mass) in the event that your estimates are even slightly off.

Allocate sufficient time

Finally, digging can be hard, time-consuming work. Allow plenty that time to dig all the write-up holes for the task before the concrete is delivered or mixed.

See more: ' Ncis How Does Gibbs Get The Boat Out, It'S Not Hard, If You Know How To Do It

Mixed concrete that should sit before being poured right into place have the right to partially or even totally set. This can an outcome in far-reaching waste native hardened, unused concrete or create air pockets and also compromised stamin from putting concrete the is too thick.