Fencing and pool volume in metres and litres
6 min read · Updated 2026-10-12 · BuildCalc
Two jobs that look unrelated share the same problem: a metric property, or a metric product, measured in a country where the units are not the ones you grew up with. A fence has to be measured to the post, and a pool has to be dosed by volume, and both go wrong quietly when the units slip.
Measuring a boundary for fencing
A fence line is the sum of the straight runs between corners, plus any curved or sloping sections measured along the actual line rather than by plan dimensions. Walk the boundary with a tape or wheel and record each run separately, because that is also how the posts divide up.
Post spacing depends on the material and the wind load, typically 1.8 to 2.5 metres for closeboard timber and up to 3 metres for light panels. Divide the total length by the spacing to get the post count, then add one, because the last run is almost never an exact multiple of the spacing and you need the closing post.
Allowing for gates, posts and waste
Gate openings and corner posts take material out of the runs and add their own. A standard single gate is about 1 metre wide, and each corner post is considerably thicker than the infill, so each corner reduces the length of the adjacent run by roughly a post width.
Fencing material is also sold in fixed lengths — commonly 1.8 or 2.4 metres — and each cut wastes a little. Order whole lengths rather than the exact total, and keep the offcuts, because they are the pieces needed to close the gaps where two lengths meet at an angle.
Pool volume in litres
Almost everything in pool care is dosed per volume of water, so the volume has to be right or every chemical dose is wrong with it. A rectangular pool is length times width times depth, with the depth averaged if the floor slopes. A pool 8 metres by 4 metres with a shallow end at 1.2 metres and a deep end at 2 metres has an average depth of 1.6 metres, giving 51.2 cubic metres.
One cubic metre is a thousand litres, so 51.2 cubic metres is 51,200 litres. In imperial the same pool would be about 134,000 US gallons, and the arithmetic is the same — which is why a pool shop asks for the volume before selling anything.
Round it, record it, and use it consistently
Do not chase precision. Nobody doses to the nearest litre, and a rounded figure that is written down near the pump is far more useful than an exact one that lives only in a calculation. Round to something defensible, record it, and use the same number every time you adjust chlorine, pH or stabiliser.
Remember to exclude steps, spas and attached features unless you intend to dose them separately, and note that the figure is the water volume rather than the shell volume, which is slightly smaller.
Run your own numbers
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Common questions
How far apart should fence posts be?
Typically 1.8 to 2.5 metres for closeboard timber fencing, and up to 3 metres for lightweight panels. Closer spacing resists wind better but costs more posts.
How many litres of water does my pool hold?
Multiply length times width times average depth in metres to get cubic metres, then multiply by 1,000. An 8 × 4 metre pool averaging 1.6 metres deep holds about 51,200 litres.
Do I need to include steps and the spa?
Not unless you are dosing them separately. Exclude them from the main volume, but keep their water in mind if you are treating the whole system as one body of water.
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