Before building a fence in your garden, it helps to know how to work out what you need. Good planning saves money, avoids wasted trips, and makes the work feel much easier. This guide explains how to measure your fence length, choose the right products, and calculate the materials required, including fence posts, rails, boards, and gravel boards.
Start With A Clear Plan
Begin by deciding what the fence is for. Do you need privacy, security, or a smart boundary line? Your answer will help you select a fence style, the right fence height, and the best materials for the job. Timber fencing is popular because it looks natural and is easy to adjust, but metal and composite options can also work well if you want less upkeep.
It also helps to sketch your garden and mark where the fence will go. Include corners, changes in direction, and any place where you may need a gate. A simple plan makes it easier to count the number of sections and posts later.
Measure Fence Length Carefully
To calculate materials, you need the fence length first. Measure along the line where the fence will sit, following the boundary. If the line bends, measure each straight run and add them together.
Most suppliers and a fencing calculator will ask for the length in metres, so it is worth recording your measurements that way. If you measure in feet, convert it before you order. Once you have the total length in metres, you can work out how many panels, boards, and posts you will require.
Check Levels And Ground Conditions
Your garden ground may not always be level. Slopes can change how many panels you need, the height of the posts, and whether you should use gravel boards. Walk the full fence line and look for dips, high spots, and soft ground.
If the ground slopes, you may need to step the panels down or follow the slope with featheredge boards. This choice affects the dimensions of the boards and the number of rails you need. It can also change how deep you dig for each post.
There are two common ways to build a timber fence. One option is pre-made panels fixed between posts. The other is building the fence from individual boards and rails, often called closeboard fencing.
Panels can be quicker because you fix whole sections at once, but they come in set sizes. Board fencing gives more control, which can help on uneven ground, but it can require more cutting and careful fitting. Your choice changes how you calculate materials, so decide this early.
Fence posts sit at the ends of every section and at corners, gates, and changes in direction. The spacing between posts often depends on your panel width or your chosen bay size.
If you are using panels, the number of posts is usually one more than the number of panels in a straight run. For example, if you need 10 panels, you will normally need 11 fence posts, plus extra posts for corners and gates.
If you are building from boards, you still need posts at regular gaps. Many people place posts around 1.8 metres to 2.4 metres apart, depending on the fence style and how strong it needs to be. Closer spacing can make the fence feel sturdier, but it will add to the number of posts you need.
Fence height affects almost every part of the order. Taller fencing can require longer posts, more rails, and sometimes thicker boards. A common mistake is buying posts that are too short.
A simple rule is that posts should go into the ground by roughly a third of the post length, depending on soil and exposure. So, if your fence height is 1.8 metres above ground, you may require a post that is around 2.4 metres long, or more in soft ground. This gives enough depth for strength once the post is set.
Gravel boards sit at the bottom of the fence, between the posts. They help protect timber panels or boards from damp soil and splashes, which can help the fence last longer. A gravel board can be concrete or timber, and both need the correct dimensions to match your fence panels or bays.
If you are using panels, you will often need one gravel board per panel. If you are building from boards, you may use a gravel board along each bay as well. When measuring, treat gravel boards as part of the section count, just like panels. If you are buying a single gravel board for repairs, make sure it matches the thickness and height of what you already have.
Many fences use two rails for shorter heights and three rails for taller fencing. A helpful guide is that higher fences often need extra rails to reduce movement in strong winds. If you are building from boards, rails are a key part of the structure, so it is worth choosing strong timber and allowing for joins where rails meet posts.
When you calculate rails, count how many bays you have, then multiply by the number of rails per bay. You should also allow extra rails if your design includes a top rail, a bottom rail, or added bracing near a gate.
If you are using panels, you can calculate the number you need by dividing the total fence length by the width of one panel, then rounding up. Most panels are made to match common post spacing, but always check the product dimensions before you order.
If you are using boards, you need to work out how many boards fit across the fence length. Measure the width of one board, then add the gap you want between boards if your design includes spacing. Divide the fence length by the combined width and round up to get the number of boards required. This part is where a fence calculator can be a big help, because it reduces mistakes when working with lots of small parts.
Concrete, Post Mix, And Fixings
Each post usually needs concrete or post mix to keep it firm. The amount you require depends on the size of the post hole and the soil type. Softer ground often needs a wider or deeper hole, which increases the amount of concrete needed.
You will also need fixings such as screws, nails, brackets, or clips. The exact number depends on the fence style and the products you select, but it is wise to add extra fixings to your basket in case some bend, snap, or get lost during work.
Gates, Corners, And End Posts
Gates and corners need stronger support than a straight run. A gate post may need to be thicker, set deeper, or supported with stronger fittings because it takes more force over time. Corner posts may also need extra fixings or rails to keep both fence runs steady.
When you calculate materials, treat these points as special cases. They often change the number of posts, the type of post you need, and the amount of concrete required.
Using An Online Fence Calculator Or Fencing Calculator
If you want a quicker method, use an online fence calculator or fencing calculator. These tools usually ask for fence length, fence height, post spacing, and whether you are using panels, boards, rails, or gravel boards. A good calculator will also estimate how many fixings and how much post mix you might require.
Please note that calculator results are only as accurate as the measurements you enter. Always double-check your fence length and length in metres before you place an order, and make sure the product dimensions match what the calculator assumes.
Allow For Waste And Future Repairs
Even careful planning can lead to small errors, damaged boards, or a panel that cracks during fitting. It is sensible to add around 10% extra materials to your order, especially for timber boards, fixings, and rails. This gives you a buffer without buying far too much.
If you have space, keeping spare boards and a spare gravel board can also help with quick repairs later, especially after storms.
Final Checks Before You Order
Before you add everything to your basket, read each product description carefully and confirm the dimensions. Make sure your posts match your fence height, your rails match your bay width, and your gravel boards match your panel width and height. It also helps to check delivery details, because longer posts and heavy gravel boards can have different delivery rules. If anything is unclear, contact us for help before you order, so you do not end up with the wrong products.
Please note that if you live in an area with specific rules, you may need to check local guidance about maximum fence height, especially at the front of a property or near roads.
Are you looking for garden fencing near you? If you require garden fencing installation and supply in Milton Keynes, Buckinghamshire contact us today. Our garden design experts can supply and install beautiful garden decking for you and your family to enjoy for years to come.
