Fence Calculator

How to Calculate Fence Panels for a Garden

Working out how many fence panels you need is simpler than most people think. Here is the step-by-step method that fencing contractors use:

1. Measure the total fence run - use a tape measure or laser along the line where the fence will go. Record the length in metres. For example, a typical rear garden boundary might be 12 metres.
2. Choose your panel width - standard UK fence panels are 1830mm (6 feet) wide. This is by far the most common width stocked at Wickes, B&Q and Screwfix.
3. Divide length by panel width - convert to millimetres first. 12m = 12,000mm. 12,000 ÷ 1,830 = 6.55 panels. You need 6 full panels plus one cut panel (roughly 1,000mm wide).
4. Count posts - you need one more post than the number of bays (panels). For 7 bays, that’s 8 posts. If one end butts against a wall, subtract one post.
5. Add fixings - postcrete or concrete for each post, gravel boards for each bay, and panel clips or arris rails depending on your panel type.

For the example above (12m fence with standard panels), you need 7 panels (6 full + 1 cut), 8 posts, 8 bags of postcrete, and 7 gravel boards.

UK Standard Fence Panel Sizes

UK fence panels come in a limited range of standard sizes. The width is almost always 1830mm (6ft), but heights vary depending on your needs and any planning restrictions.

All standard UK fence panels are 1830mm (6ft) wide. The panel width includes the frame, so the actual gap between posts is 1830mm. Posts are typically 75mm or 100mm square.

Postcrete vs Concrete for Fence Posts

There are two main ways to set fence posts in the ground in the UK:

Postcrete (fast-set post mix) - a pre-mixed powder that you pour into the hole around the post, then add water. It sets in about 10 minutes. One 20kg bag is enough for one post. Postcrete is the most popular choice for DIY fence installations because it is fast, clean and requires no mixing. Brands include Postcrete by Blue Circle and Post Fix by Hanson.

Standard concrete mix - you mix ballast (combined sand and gravel) with cement at roughly a 5:1 ratio. For each post, you need approximately 2.5 bags of ballast (25kg each) and half a bag of cement (25kg). This is cheaper per post but slower and messier. It takes 24-48 hours to set fully.

Metpost / bolt-down spikes - a steel spike driven into the ground or a bolt-down plate fixed to concrete. No digging required. Best for firm ground or where you are fixing to an existing concrete base. One spike or bolt-down per post.

For most garden fences, postcrete is the best choice. It is slightly more expensive than mixing your own concrete but saves significant time and effort, especially when setting 8-10 posts in a day.

How Deep Should Fence Posts Be?

The general rule in the UK is to bury fence posts at least 600mm (2 feet) into the ground. This applies to standard 6ft (1800mm) fence panels.

• 600mm (24″) burial depth - the standard for 1500mm and 1800mm panels. This provides adequate stability in most UK soil types.
• 450mm (18″) burial depth - acceptable for shorter panels (900mm and 1200mm) in firm ground.
• Exposed or windy sites - consider 750mm burial for extra stability. Fences act as sails in strong wind, and UK storms regularly bring down poorly-anchored fencing.

The total post length you need is: panel height + gravel board height (if used) + burial depth. For a standard 6ft fence with 150mm gravel board and 600mm burial, you need posts at least 2550mm (about 8ft 4in) long. The most common post length stocked by UK merchants is 2400mm (8ft) or 2700mm (9ft).

Planning Permission for Fences UK

Under permitted development rights in England and Wales, you can erect a fence without planning permission provided:

• The fence is no more than 2 metres high (measured from the ground on the highest side)
• If the fence is adjacent to a highway used by vehicles (including a public footpath that is also a road), it must be no more than 1 metre high
• The property is not a listed building or in a conservation area (additional restrictions may apply)
• There is no Article 4 direction removing your permitted development rights

A standard 6ft (1800mm) fence panel plus a 150mm gravel board gives a total height of 1950mm, which is under the 2m limit. If you add a trellis on top, the combined height must still not exceed 2 metres.

Rules differ slightly in Scotland (generally 2m without permission) and Northern Ireland. Always check with your local planning authority if you are unsure.

How to Reduce Fence Costs

Fencing is one of the most expensive garden projects. Here are practical ways to keep costs down:

• Choose lap panels - standard overlap (lap) panels are the cheapest option, typically £20-£30 per panel. Closeboard panels cost £40-£60+ each.
• Use concrete posts - they last 25+ years with zero maintenance. Timber posts rot at the base after 5-15 years unless pressure-treated. The upfront cost of concrete posts is slightly higher but saves money over the fence’s lifetime.
• Buy in bulk - many UK merchants (Wickes, B&Q, Travis Perkins) offer discounts when you buy 5+ panels. Check click-and-collect prices online as they are often lower than in-store.
• Use postcrete instead of a fencer - professional fence installation in the UK costs £60-£100+ per metre. DIY with postcrete can cut costs by 50-70%.
• Include gravel boards - they cost £5-£10 each but prevent the bottom of your panels rotting, extending panel life by years.
• Time your purchase - fencing prices are lowest in autumn and winter. Spring and summer demand pushes prices up, and storms can cause temporary shortages.