Most garden jobs come down to three measurements: a length, an area and a volume. A fence run is a length, a new lawn is an area, and a raised bed full of topsoil is a volume. Get those three right and you will order the correct number of turf rolls, panels or bulk bags the first time, rather than paying for a second delivery or a skip for the surplus.

UK garden suppliers mix their units freely. Fence panels are still sold as “6 ft” panels, turf is priced per square metre, aggregates come by the tonne or the bulk bag, and plant pots are labelled in litres or centimetres. The guides below explain each one in plain terms, and the area converter handles any switch between square metres, square feet and square yards.

How do you measure the area of a garden?

Multiply the length by the width, both in metres, to get the area in square metres (m²). A rectangular lawn 10 m long and 6 m wide covers 60 m². Use a long tape or a measuring wheel, keep the tape taut and level, and measure along the edges rather than diagonally across the plot.

Few gardens are perfect rectangles. The reliable method is to sketch the plot, divide it into simple shapes, measure each one and add the results. A rectangle is length × width, a right-angled triangle is half the base × the height, and a circle is 3.14 × the radius squared. If you need a quick refresher on reading the markings, the guide to reading a tape measure covers metric and imperial blades.

How do you work out how much topsoil, gravel or bark you need?

Multiply the area in square metres by the depth in metres to get the volume in cubic metres (m³). A bed of 10 m² filled 50 mm deep needs 10 × 0.05 = 0.5 m³. Convert millimetres to metres by dividing by 1,000, so 75 mm is 0.075 m and 150 mm is 0.15 m.

Suppliers in the UK sell loose materials by volume (cubic metres or litres), by weight (tonnes) or by the bulk bag. Because a tonne of fine topsoil and a tonne of coarse gravel do not fill the same space, ask the supplier how many square metres one bag covers at your chosen depth, or what their material weighs per cubic metre. Allow a little extra for settling, levelling and uneven ground.

Depth	Depth in metres	Volume for 10 m²	Volume for 25 m²
25 mm (1 in)	0.025 m	0.25 m³	0.625 m³
50 mm (2 in)	0.05 m	0.5 m³	1.25 m³
75 mm (3 in)	0.075 m	0.75 m³	1.875 m³
100 mm (4 in)	0.1 m	1 m³	2.5 m³
150 mm (6 in)	0.15 m	1.5 m³	3.75 m³
300 mm (12 in)	0.3 m	3 m³	7.5 m³

One cubic metre is 1,000 litres, which helps when compost or bark is sold in 50-litre or 60-litre bags: 0.5 m³ is 500 litres, or ten 50-litre bags.

Garden measurement quick-reference chart

These are the conversions that come up most often when planning a UK garden. Metric values are given to sensible precision for ordering materials; the defined values are exact.

Unit	Metric	Imperial
1 foot	30.48 cm (exact)	12 in
1 yard	0.9144 m (exact)	3 ft
1 square metre	1 m²	10.76 sq ft or 1.196 sq yd
1 square yard	0.836 m²	9 sq ft
1 acre	4,046.86 m² (0.405 ha)	4,840 sq yd
1 hectare	10,000 m²	2.471 acres
1 cubic metre	1,000 litres	35.31 cu ft
1 cubic yard	0.765 m³	27 cu ft
“6 ft” fence panel width	1.83 m	6 ft
1 mm of rain on 1 m²	1 litre	about 0.22 UK gallons

What size are UK fence panels?

Most UK fence panels are 6 ft (1.83 m) wide, with heights typically from 3 ft (0.91 m) to 6 ft (1.83 m). The posts sit between the panels, so a fence run uses one more post than it has panels. Always check the supplier’s actual panel and post sizes before you calculate, because they vary slightly between ranges.

To estimate how many panels you need, divide the length of the run by the panel width plus the post width, then round up. A 20 m boundary using 1.83 m panels and 100 mm (4 in) posts needs 20 ÷ 1.93 = 10.4, so 11 panels and 12 posts, with the last panel cut down or a gap closed with a gravel board and post adjustment.

Height also matters for planning. According to the Planning Portal, a new fence, wall or gate needs planning permission if it would be over 1 m high next to a highway used by vehicles (or its footpath), or over 2 m high elsewhere. Extra rules apply to listed buildings and some estates, so check with your council if in doubt. Measure height from the ground on your side, and on sloping ground measure at the highest point.

How do you measure a slope in the garden?

Gradient is the vertical rise divided by the horizontal distance, often written as a ratio such as 1 in 20 or as a percentage. Drive a peg at the top and bottom of the slope, tie a string between them, make the string level with a spirit level, then measure the drop from the string to the ground at the low peg.

If the string is 5 m long and the drop is 250 mm, the gradient is 0.25 ÷ 5 = 0.05, which is 1 in 20 or 5%. Knowing the fall helps when you plan a patio (which needs a slight fall so rain runs away from the house), a shed base (which needs to be level) or terracing with sleepers.

How are plant pots and gutters measured in the UK?

Plant pots are usually sized by the inside diameter across the top rim in centimetres, or by volume in litres. Nursery plants are often labelled “2 L” or “9 cm”, and the two systems do not map neatly because pot shapes differ. Measure straight across the top of the pot from inside edge to inside edge, then measure the depth from the rim to the base. The plant pot size guide walks through both methods.

Gutters are measured across the top opening of the profile, in millimetres. In UK homes the most common plastic half-round size is 112 mm, but deep-flow, square and ogee profiles also exist, and a replacement section has to match the profile as well as the width. The gutter size guide explains how to identify yours safely from the ground or a secured ladder.

How big is an acre?

An acre is 4,840 square yards, or 4,046.86 m², which is a square roughly 63.6 m on each side. A hectare is 10,000 m² (a 100 m square) and equals about 2.47 acres. UK land and agricultural plots are often described in acres, while surveys and planning documents usually use hectares or square metres.

Typical domestic gardens are far smaller, so square metres are the practical unit for lawns, patios and borders. For bigger plots, paddocks and allotment sites, the area and property measurement hub covers land area, floor space and how surveyors measure.

What should you measure before ordering turf, slabs or a shed base?

• Turf and artificial grass: the area in m², plus the longest straight length, because artificial grass comes in fixed roll widths and you want to avoid unnecessary joins. Many turf suppliers sell rolls of about 1 m² each, but check the stated roll size.
• Patio slabs: the area in m² and the slab size including the joint gap, so you can count slabs per row and per column instead of dividing area by slab area alone.
• Shed base: the external footprint of the shed, plus any overhang the manufacturer recommends for the base, and the level difference across the site.
• Raised beds and borders: the internal length, width and fill depth, to work out the volume of soil or compost.
• Water butts: the roof area that drains into the downpipe. Every 1 mm of rain falling on 1 m² of roof yields up to 1 litre of water, so a 20 m² shed and greenhouse roof can collect around 200 litres from 10 mm of rain.

Guides in this section

Garden and outdoor guides

• How to measure gutter size (UK): identify the profile and width of half-round, square and deep-flow gutters.
• How to measure plant pot size (UK): diameter, depth and litre sizes explained for repotting.

Converters for garden projects

• Area converter: square metres, square feet, square yards, acres and hectares.
• Volume converter: cubic metres, litres and gallons for soil, compost and water butts.
• Feet to cm converter: for old plans, fence heights and timber lengths sold in feet.
• Weight converter: tonnes, kilograms and pounds for aggregate deliveries.

Latest garden and outdoor guides

For the background to metric and imperial units, start with the units of measurement guide. Related hubs cover home and DIY measuring and measuring tools and how to use them, including tape measures, spirit levels and measuring wheels.

Frequently asked questions

How do I measure an irregular-shaped garden?

Sketch the garden, divide it into rectangles, triangles and circles, measure each shape in metres and work out its area separately. Add the areas together for the total in square metres. For curved edges, take several measurements and treat the shape as a series of narrow rectangles.

How do I convert square feet to square metres?

Multiply square feet by 0.0929, or divide by 10.764. For example, 500 sq ft is about 46.5 m². One square foot is exactly 0.09290304 m² because one foot is exactly 0.3048 m.

How much gravel do I need for 10 square metres?

Multiply the area by the depth in metres. At 50 mm deep, 10 m² needs 0.5 m³ of gravel. To convert that volume into tonnes or bulk bags, use the weight per cubic metre or the coverage figure your supplier gives for that particular stone.

Do I need planning permission for a 6 ft fence?

A 6 ft fence is about 1.83 m, which is under the 2 m limit the Planning Portal gives for most boundaries. Next to a highway used by vehicles, or its footpath, the limit is 1 m. Listed buildings and properties with restrictive conditions can have different rules, so check with your local council.

What is the best tool for measuring a large garden?

A 30 m fibreglass tape or a measuring wheel is the most practical choice for long boundaries. A laser measure works well where there is a solid target such as a wall or fence. For land plots, online mapping tools give a useful first estimate, but measure on site before ordering materials.

Sources

• Planning Portal: height restrictions for fences, gates and garden walls
• The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2 Part 2 Class A
• Weights and Measures Act 1985, Schedule 1 (definitions of the yard, acre and other units)
• National Physical Laboratory (NPL): the UK’s national measurement institute