Getting the right amount of composite fencing is one of those things that seems simple—until you’re halfway through the project and realize you didn’t order enough. Or worse, you’ve got a pile of extra panels that cost more than they should have.
To avoid frustration (and extra trips to the store), it’s important to measure carefully and account for all the details before making a purchase. Here’s how to get it right the first time.
Start with Accurate Measurements
The first step is straightforward: measure the area where you’ll be installing your fence. Grab a measuring tape (or a measuring wheel if you’re working with a large space) and determine the total length of your fence line.
If your yard is a perfect rectangle, this will be easy. Just measure along the perimeter where the fence will go. But if you’re dealing with curves, angles, or property line irregularities, take separate measurements for each section.
And don’t forget about gates! If you’re installing one, subtract its width from the total fence length since a gate will replace a section of fencing.
Once you have the total length, write it down. This number is the foundation of your entire fencing plan.
Choosing Your Fence Panels and Posts

When you buy composite fencing online, it is typically sold in pre-made panels, usually 6 or 8 feet wide. To figure out how many panels you need, divide your total fence length by the width of the panel you’re planning to buy.
For example, if your fence is 100 feet long and you’re using 6-foot panels:
100 ÷ 6 = 16.67 panels
Since you can’t buy a fraction of a panel, round up to 17. It’s always better to have a little extra than to come up short.
Now, what about posts? Every panel needs to be attached to a post, which means you’ll need one more post than the number of panels. If you have 17 panels, you’ll need 18 posts—one at each end and one between each panel.
Corners and gate areas may require specialized posts, so factor those in if needed.
Thinking Beyond Just Panels
It’s tempting to focus only on panels and posts, but there are other materials to consider. You may need:
- End posts for places where the fence doesn’t connect to another section
- Corner posts if your fence turns at sharp angles
- Brackets and fasteners to secure the panels properly
- Post caps to protect the top of your posts and give the fence a finished look
These details matter. The last thing you want is to start installing and realize you’re missing essential pieces.
Allowing for Extra Material
No matter how carefully you plan, there’s always a chance you’ll need a little more than expected. Maybe a panel gets damaged during installation, or your yard isn’t as level as you thought, requiring an adjustment.
A good rule of thumb is to order 5-10% more than your calculated amount. If you need 17 panels, consider buying 18 or 19 to be safe. The same goes for posts and fasteners. It’s better to have a little extra than to scramble for last-minute replacements.
Accounting for Slope and Uneven Ground
If your yard is perfectly flat, your calculations will be straightforward. But if you’re dealing with a sloped or uneven landscape, things get a little trickier.
On sloped ground, fencing is typically installed using either a stepped or racked method. Stepped fencing follows the incline with each panel remaining level, creating a stair-step effect. Racked fencing, on the other hand, angles the panels to follow the slope more smoothly.
Whichever method you choose, be aware that adjustments may be needed, which could slightly alter the number of panels required. It’s a good idea to consult the installation guidelines for your specific fence style to ensure you’re ordering the right amount.
Finalizing Your Shopping List

By now, you should have a solid idea of how much composite fencing you need. Here’s a quick recap to make sure you’re covering all bases:
- Total fence length measured
- Panel size chosen and number of panels calculated
- Correct number of posts (including corners and ends)
- Additional materials like post caps, brackets, and fasteners
- A little extra ordered for unexpected issues
With everything planned out, you’ll be ready to order exactly what you need—without overspending or scrambling for last-minute fixes.
A Smooth Installation Starts with Smart Planning
Taking the time to calculate your fencing needs before buying will save you from unnecessary stress, wasted money, and mid-project delays. It’s all about getting the right measurements, accounting for obstacles, and ordering just a bit extra to cover any surprises.
Once your materials are in hand, installation will be much easier, and you’ll be on your way to a great-looking, long-lasting composite fence.