Fence Calculator
A fence is a shopping list, not a single number: panels, one more post than panels, a gravel board under each panel, concrete for every post and clips to hold it all together. Enter the run, the panel size and the height, and this calculator counts every item, rounds each one up to whole units and tells you how long the posts must be.
Your measurements
Check your order
Your fence and post order
- Confirm the fence run, corners, gates and post spacing from the project specification.
- Check hole dimensions and the chosen concrete product’s yield before ordering bags.
- Plan bracing and alignment checks; a quantity estimate does not specify safe footing dimensions.
Tools for this job
Measure the full fence run and mark post positions before digging. A post level helps keep each post upright during installation.
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- Keep posts upright while fixing
Post level
Johnson 175-O post level
For checking that a post is upright while positioning and bracing it. Recheck alignment after fixing or placing concrete, before it sets.
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Long tape measure
Komelon 6611 100-foot open-reel tape
For measuring longer outdoor runs and marking out areas. Keep the tape straight and use the same units throughout; this listing is for the 100-foot model.
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Already have suitable tools? Reuse them. These are optional product suggestions, not a complete equipment list or a hands-on comparison. Amazon may redirect Amazon.com links to local products or search results. Amazon.nl links search for alternatives, which may differ in brand, size and specification. Check suitability, seller, delivery and any import costs on your chosen store before ordering.
How many fence panels and posts do I need?
Divide the run by the panel width and round up: a 20 m run of 1.83 m panels is 10.9, so 11 panels, with the last one cut to fit. Posts are always one more than panels on a straight run, because every panel needs a post at each end and neighbouring panels share them. Each corner adds a post, because a panel cannot bend, and each gate adds one, because the gate breaks the run into two separate sections.
The post length is where people go wrong. A post has to cover the panel, the gravel board underneath it and the part buried in the ground, so a 1.8 m panel on a 150 mm gravel board with 600 mm in the ground needs a 2.55 m post, which means buying 2.7 m timber. Buy 2.4 m posts for that fence and you either bury them too shallow or the panel sits above the post top.
The formula
Sizes and allowances the calculator uses
| Item | Typical size or rate | Notes |
|---|---|---|
| Fence panel | 1.83 m (6 ft) wide; 0.9 to 1.8 m high | Lap, closeboard, hit-and-miss and slatted panels share the same width |
| Timber post | 75 x 75 mm or 100 x 100 mm; 2.4, 2.7 or 3.0 m long | 100 mm for gates and exposed sites |
| Slotted concrete post | 100 x 100 mm; 2.36 to 3.0 m | Intermediate, corner and end posts are different products |
| Gravel board | 150 or 300 mm high, one per panel | Timber or concrete; keeps the panel off the wet ground |
| Depth in the ground | 600 mm (2 ft) for 1.8 m fences | Roughly a quarter of the post; deeper in soft ground |
| Post-mix | 2 x 20 kg bags per 600 mm hole | See the concrete calculator, post hole shape, for other hole sizes |
| Panel clips | 4 per panel on timber posts | U-clips or angle brackets; none needed with slotted concrete posts |
| Fence treatment | 4 to 8 m² per litre per coat | Rough-sawn timber drinks more than planed |
Worked example
A straight 20 m run of 1.83 m (6 ft) panels, 1.8 m high, on timber posts with 150 mm gravel boards, posts set 600 mm deep, two bags of post-mix per post, and two coats of treatment on both sides at 6 m² per litre.
Panels = 20 ÷ 1.83 = 10.9, rounded up to 11 panels. Posts = 11 + 1 = 12 posts. Gravel boards = 11. Post length = 1.8 + 0.15 + 0.6 = 2.55 m, so buy 2.7 m posts. Post-mix = 12 × 2 = 24 bags. Clips = 11 × 4 = 44. Treatment = 20 × 1.8 × 2 sides × 2 coats ÷ 6 = 24 litres.
Add a gate and a corner to the same run and the post count goes to 14 while the panel count stays at 11, because the gate width comes out of the run. That is why the calculator asks for gates and corners separately.
Timber or concrete posts?
- Timber posts are cheaper, lighter and easier to fix to, but they rot at ground level in 10 to 15 years unless they are pressure treated and kept out of standing water. Panels are held with four clips each.
- Slotted concrete posts last far longer and the panels simply drop into the slots, so a damaged panel is swapped in minutes. They are heavy, need two people, and the corner and end posts are separate products with slots on the right faces.
- Concrete gravel boards pair naturally with concrete posts; timber gravel boards need cleats or clips on a timber post.
- Whichever you choose, post-mix quantities are the same: the hole, not the post, decides how much you need. The concrete calculator works it out for any hole size with its post hole shape.
Finishing the job
A new fence needs treating unless it arrived pressure treated in the colour you want, and even then a coat of treatment every two or three years is what keeps it standing. Rough-sawn panels soak up 4 to 8 m² per litre per coat, so a 20 m fence painted both sides takes around 24 litres for two coats; the paint calculator covers smooth or masonry surfaces. Fill the post holes with gravel or soil above the concrete so water drains away from the post.
Post caps, finials, a 50 mm capping rail along the top and galvanised nails or screws for the gravel board cleats are the small items that get forgotten. Buy them with the panels and you save a second trip.
Mistakes that cost a return trip
- Measuring the run between the walls and forgetting the width of the gate, so the last panel does not fit.
- Buying 2.4 m posts for a 1.8 m panel on a gravel board. The post is 150 mm short before it is in the ground.
- Skipping the gravel board. The panel sits in wet soil and rots along the bottom rail within a few years.
- Setting the posts to the panel width plus nothing. Timber posts need a 5 to 10 mm gap each side for the clips; concrete slots take the panel exactly.
Sources and assumptions
Panel count divides the run less gates by the selected panel width. Posts, gravel boards and basic fixing quantities are a budget estimate for a simple panel fence.
- Jacksons Fencing: slotted post planning and installation: The manufacturer explains that actual run length includes panel width and the contribution of intermediate and end posts; its fixing and footing guidance is specific to that system.
Before using this estimate
- The calculator does not include the post width in panel spacing or draw each bay. Count each straight run, corner and gate on a sketch before ordering.
- The selected bag allowance, clips and post length do not establish suitability for the ground, wind exposure or gate weight. Check the complete fencing system instructions.
Source notes reviewed . See how we check calculations and handle corrections.
Planning your order
Check the inputs before buying: measure the surfaces you need, then apply an allowance and round to whole packs. The guides include worked examples you can follow alongside this calculator.
Published by OrderEnough. This is a planning estimate: check the product specification and the assumptions above before ordering. Last updated . Read how we source our figures on the methodology page.