Plan Post Spacing, Holes, Bags & Concrete Before You Dig
Estimate fence post count, post-hole concrete, cubic yards, cubic feet and concrete bags for wood, metal and composite fence posts. Plan straight fence runs, individual round holes, mixed line/corner/gate posts and optional concrete cost from your own dimensions.
Plan the fence run first, then estimate concrete for standard, corner, gate and other post holes.
Estimate posts for one straight continuous run, then calculate concrete around each embedded post.
Adds posts beyond the straight-run spacing count.
Straight-run spacing estimate only. Gates, corners, slopes, terminal assemblies and manufacturer-specific fence systems can change post count.
Calculate concrete for identical round holes while subtracting the volume occupied by the embedded post.
Assumes the post extends through the full entered hole depth. Irregular holes can require more concrete than ideal geometry predicts.
Combine two post groups when terminal, corner or gate posts use larger holes than ordinary line posts.
Uses square-post displacement for both groups. If your actual posts are round, use the Round Post Holes mode for a more exact displacement estimate.
Convert a known concrete requirement into 40, 60 and 80 lb bag estimates or optional ready-mix cost.
Bag yields are approximate planning values. Always use the yield printed on the concrete product you actually buy.
A Concrete Fence Post Calculator combines two jobs that are often estimated separately: deciding how many fence posts are needed along a run and estimating the concrete required around those posts. For a straight fence, post count depends on run length and the maximum spacing you choose. Concrete quantity then depends on hole diameter, hole depth, post dimensions and the number of holes.
The calculator is useful for privacy fences, picket fences, agricultural boundaries, garden fences, decorative screens, chain-link terminal posts, gate posts and many other fence layouts. It can also help compare a standard line-post hole with a larger corner or gate-post hole so those heavier locations are not accidentally priced at the same concrete quantity.
This is primarily a material-planning tool. It does not decide the correct post spacing, post size, hole diameter, embedment depth, wind resistance or frost depth. Those inputs depend on the fence system, height, material, soil, climate, local code, manufacturer instructions and structural demands.
Divide a straight run into equal or shorter spaces so spacing does not exceed your chosen maximum.
Calculate cylindrical hole volume and subtract the embedded wood or metal post volume.
Compare approximate 40, 60 and 80 lb bag quantities for small fence-post projects.
Enter your local ready-mix price per cubic yard for a simple material comparison.
Start with the fence layout rather than the concrete. Mark corners, ends, gates and changes in direction first because those locations often require dedicated posts. Then measure the straight run lengths between those control points. If you know the maximum post spacing permitted by your fence design, the Fence Run Planner divides the run into enough equal spaces so no bay exceeds that spacing.
Measure each straight section between corners, ends or gate assemblies.
Use the spacing required by your fence design or manufacturer.
Use the required hole diameter and embedment depth for that post type.
The calculator subtracts the volume displaced by the embedded post.
Review cubic yards, concrete bags, allowance and optional cost.
For one straight continuous fence run with a post at each end, the calculator first determines how many spaces are needed so no space is longer than your selected maximum. Because partial spaces require another bay, the number of spaces is rounded up. One additional post closes the last end of the run.
Ceiling means round any fractional result up to the next whole number.
Use “extra posts” only for posts not already represented by the two run-end posts.
A property boundary with several separate runs should be broken into sections rather than treated as one long straight line. Shared corner posts should be counted once. Gates can add terminal or hinge/latch posts depending on the system.
A drilled or augered post hole is usually approximated as a cylinder. Its gross volume is based on radius squared multiplied by depth and π. If the fence post is embedded in that concrete, the post itself occupies part of the hole. The calculator subtracts that displacement to avoid treating the post space as concrete.
Convert inches to feet before calculating cubic feet.
Square posts use width × width × depth. Round posts use π × post radius² × depth.
One cubic yard contains 27 cubic feet.
Fence post spacing is not a universal concrete rule. It is part of the fence system. Panel width, rail span, picket material, post stiffness, fence height, wind exposure, soil and manufacturer instructions all affect the allowable spacing. Prefabricated fence panels may effectively set the bay width, while site-built fences can allow a different layout.
The calculator therefore asks for your maximum post spacing instead of automatically entering a value. If a straight 100-foot run is divided using an 8-foot maximum, the tool rounds the number of bays up so each actual bay becomes slightly shorter than 8 feet. This avoids creating one oversized final bay.
Panel width often controls post centers. Confirm the actual panel and bracket dimensions before layout.
Rail span and structural design can control spacing, especially for tall privacy fences.
Line, terminal, corner and gate posts can use different post sizes and footing requirements.
Hole depth affects stability, frost performance and material quantity, so it should not be chosen from the concrete calculator alone. QUIKRETE’s consumer post-setting instructions describe a general approach based on a fraction of the above-ground post height plus additional depth and also recommend checking local building codes. That guidance is useful as an installation reference, but it is not a substitute for local frost, wind or structural requirements.
Some code provisions for particular fences, jurisdictions or materials specify minimum embedment, footing dimensions or maximum spacing. Other areas regulate fence height, setback and permits rather than prescribing one universal concrete footing. When frost is significant, local required depth can be much greater than a generic post-setting example.
Use the exact hole depth required for your fence, then let the calculator determine the material quantity. Increasing hole depth by only a few inches across dozens of posts can noticeably increase the total number of bags.
Hole diameter must leave enough space around the post for the specified concrete or post-setting material and must satisfy the structural and installation requirements of the fence. QUIKRETE’s official post-setting guidance gives an example approach based on making the hole several times the post width, but actual project requirements may differ.
A 4-inch nominal wood post does not mean every project needs the same hole diameter. A short garden fence and a tall solid privacy fence see very different wind loading. Gate posts also carry hinge forces and gate weight, while corner posts can receive rail or wire forces from more than one direction. Those locations frequently need a larger post, deeper embedment or larger footing depending on design.
The Line + Gate Posts calculator exists because a fence often contains more than one foundation size. Ordinary line posts repeat along straight runs. Terminal, corner and gate posts can be structurally more demanding and may use larger post sections or larger/deeper concrete holes.
Enter the standard line-post group separately from the heavier group. The calculator totals the concrete from both. This is more accurate than multiplying one average quantity by the total number of posts, especially when only a few large gate posts use substantially more concrete.
For a driveway gate, remember that the hinge-side post may be different from a simple latch-side terminal post. Automated gates can also introduce equipment pads, conduit and manufacturer-specific foundations that should be estimated separately.
Fence posts are often small enough to use bagged concrete rather than ready-mix. The calculator converts total cubic feet into approximate bag counts using planning yields for 40, 60 and 80 lb bags. Because actual yield varies by product, always compare the result with the yield printed on the exact bag you plan to buy.
| Bag Size | Planning Yield Used | Approx. Bags per 1 ft³ | Best Use | Reminder |
|---|---|---|---|---|
| 40 lb | 0.30 ft³ / bag | 3.34 | Small holes / lighter handling | Verify manufacturer yield |
| 60 lb | 0.45 ft³ / bag | 2.23 | Common DIY post work | Verify manufacturer yield |
| 80 lb | 0.60 ft³ / bag | 1.67 | Fewer bags for larger jobs | Verify manufacturer yield |
If the result approaches several cubic yards, compare bag handling and mixing time with local ready-mix or short-load options. The Concrete Truck Capacity Calculator can help evaluate delivery volume for larger fence, wall or site projects.
Perfect cylinders rarely exist in soil. Auger wobble, loose soil, bell-shaped bottoms, collapsed sides and hand-digging can make actual holes larger than the nominal diameter. Some material can also remain in mixing tubs, wheelbarrows or tools. An allowance helps bridge the gap between ideal geometry and field conditions.
The calculator defaults to an editable 10% planning allowance, not a mandatory rule. Clean machine-augered holes in stable soil may need less extra material, while rough hand-dug holes or loose ground can need more. If you measure the actual holes after excavation, update the diameter and depth rather than relying only on a waste percentage.
The calculator can subtract either square/rectangular or round post displacement, so it works for common wood and metal shapes. The material itself affects installation details beyond volume. Wood posts raise questions about treatment, moisture exposure and decay resistance. Steel posts may use smaller diameters but different brackets, coatings or cap systems.
Do not assume the same embedment or footing design just because two post materials occupy a similar volume. The structural properties and connection to rails or panels can differ substantially. Use the fence manufacturer’s installation instructions or the project design for spacing and footing requirements.
Sloping sites complicate both spacing and depth. A plan-view horizontal fence distance is not always the same as the measured ground-surface distance on a steep slope. Stepped fence panels can also change the number of posts because each step may need to align with a post.
For a long slope, divide the fence into straight layout segments and calculate each run separately. Keep corner posts from being double-counted where two segments meet. Hole depth should still be measured according to the project’s required embedment below finished grade at each post location.
Suppose a straight fence run is 96 feet long and the selected fence system allows a maximum spacing of 8 feet. The run contains 12 spaces, so it requires 13 posts before adding any special gate or corner posts. If every post uses the same round hole, the calculator then multiplies the net concrete per hole by 13.
If two of those locations actually use larger gate posts, the better workflow is to calculate the ordinary line-post group and the gate-post group separately. This prevents the larger holes from being understated and avoids applying the larger footing to every line post.
For an L-shaped or multi-side fence, calculate each straight run and reconcile shared corners once. A site sketch with post numbers is often the easiest way to prevent double-counting.
Fence post concrete is often part of a larger outdoor project. Use the related tools below to estimate other concrete and reinforcement quantities without mixing different calculations together.
For consumer installation guidance, see QUIKRETE’s official Setting Posts in Concrete instructions. They provide a practical example of sizing and preparing post holes, adding a gravel base and placing concrete around posts.
Local code can differ. The ICC Digital Codes library shows how adopted building codes and local amendments can contain jurisdiction-specific fence, footing, frost and wind provisions. For general concrete education and standards resources, visit the American Concrete Institute.
The calculator treats a typical drilled fence-post hole as a cylinder and subtracts the embedded post volume from the concrete-filled zone.
Hole diameter: the ideal circular width of the excavation.
Hole depth: the entered below-grade depth occupied by concrete/post.
Post displacement: concrete is reduced by the volume of the embedded post.
Allowance: optional extra material accounts for imperfect field geometry.
Answers to common questions about fence post spacing, concrete volume, bag quantity and post-hole planning.