How to Measure a Garden in Square Metres (UK Guide)

Quick answer: For a rectangular garden, multiply the length by the width in metres: a 10 m × 6 m lawn is 60 m². For irregular gardens, split the plot into rectangles, triangles and circles, work out each area and add them together, subtracting beds, paths or ponds you do not want to include.

Garden suppliers price turf, seed, gravel, fencing panels and weed membrane by the square metre, so a reliable area figure saves money on almost every outdoor project. This guide belongs to our garden measuring guides and covers straight-sided plots, awkward shapes, curved borders and slopes, with worked examples you can copy.

Table of Contents

What do you need to measure a garden?

A long tape measure, some pegs or canes, and paper for a sketch. A 30 m open-reel tape is ideal for gardens because a 5 m pocket tape means many short measurements, each adding a little error.

Open-reel tape (10 m to 30 m) or a measuring wheel for long runs; our guide to reading a tape measure explains the markings
Garden canes or tent pegs to mark corners and hold the tape end
Graph paper or a notebook for a rough plan
A calculator, or the area converter if you need square feet as well

How do you calculate the area of a rectangular garden?

Multiply length by width, both in metres, and the answer is in square metres. A lawn 12 m long and 5.5 m wide is 12 × 5.5 = 66 m². If you measured in centimetres, divide each figure by 100 first; if you measured in feet, multiply the square-feet answer by 0.0929 to get square metres.

Peg the corners. Push a cane into each corner of the area you want, at the edge of the lawn or border rather than at the fence if there is a bed in between.
Measure both long sides. Keep the tape taut and level, not following dips in the ground. If the two sides differ, the shape is not a true rectangle; use the average for a rough figure or treat it as a trapezium.
Measure both short sides in the same way.
Multiply the length by the width and round to one decimal place.

How do you measure an irregular-shaped garden?

Divide it into simple shapes, calculate each one, then add them up. Almost any garden can be broken into rectangles, right-angled triangles and circles or part-circles, and the formulas for those are short.

A lawn that looks awkward on the ground becomes three easy sums: 60 + 12 + 9 − 3.14 = 77.86 m².

Shape	Formula	Example
Rectangle or square	length × width	10 m × 6 m = 60 m²
Right-angled triangle	½ × base × height	½ × 6 m × 3 m = 9 m²
Trapezium (two parallel sides)	½ × (side a + side b) × distance between them	½ × (8 + 6) × 5 = 35 m²
Circle	π × radius²	3.1416 × 2² = 12.57 m²
Semicircle	½ × π × radius²	½ × 3.1416 × 3² = 14.14 m²

For a triangle that is not right-angled, measure the base and then the perpendicular distance from the base to the opposite corner; that perpendicular is the “height”. For a circular bed, measure straight across through the centre and halve it to get the radius.

How do you measure a garden with curved edges?

Use the offset method: lay a straight baseline, measure out to the curve at equal intervals, and average the offsets. It is a standard surveying technique and handles flowing borders and kidney-shaped lawns well.

Halve the first and last offsets, add the rest, then multiply by the spacing. Closer spacing gives a more accurate result on tight curves.

Lay a baseline. Stretch the tape along a straight edge such as a fence, path or patio, from one end of the curved area to the other.
Mark equal intervals. Every 1 m or 2 m along the baseline, depending on how tight the curve is.
Measure the offsets. At each mark, measure at right angles from the baseline to the curved edge. A builder’s square or the 3-4-5 rule helps keep the tape square.
Apply the formula. Area = spacing × (half the first offset + all the middle offsets + half the last offset).

In the example, the offsets at 2 m spacing give 2 × (1.5 + 20.4 + 1.3) = 46.4 m². The method slightly underestimates outward bulges and overestimates inward ones between offsets, so halve the spacing on sharply curving edges.

Can you measure a garden using an online map?

Yes, for a rough figure. On a computer, Google Maps lets you right-click, choose “Measure distance” and click around the boundary; closing the shape also shows an area. Treat the result as an estimate, because aerial imagery can be slightly offset and trees or shadows hide the true edge of a lawn.

HM Land Registry title plans are also approximate for this purpose. Under section 60 of the Land Registration Act 2002, the boundary shown on a registered title is a “general boundary” unless it has been formally determined, so it does not fix the exact line. Measure on the ground for anything you are buying materials for.

Does a sloping garden have a bigger area?

Yes. The surface of a slope is larger than its flat plan area, so measure along the ground when you are buying turf, seed or membrane. A bank that is 4 m across on a plan but rises 3 m has a surface 5 m long, because 3² + 4² = 5². Maps and drawings show the plan area; a tape laid on the ground gives the surface area.

How do you convert garden area to square feet, yards or acres?

One square metre is 10.764 square feet, or 1.196 square yards. An acre is 4,046.86 m² and a hectare 10,000 m², so most UK gardens are a small fraction of either.

Square metres	Square feet	Square yards	Acres
20 m²	215 sq ft	23.9 sq yd	0.005
50 m²	538 sq ft	59.8 sq yd	0.012
100 m²	1,076 sq ft	119.6 sq yd	0.025
150 m²	1,615 sq ft	179.4 sq yd	0.037
200 m²	2,153 sq ft	239.2 sq yd	0.049
500 m²	5,382 sq ft	598.0 sq yd	0.124
1,000 m²	10,764 sq ft	1,196.0 sq yd	0.247

Estate agents and older garden books often quote square feet or yards, while UK landscaping suppliers sell by the square metre. Property floor areas follow similar rules; see our area and property measurement guides for indoor spaces.

How accurate does a garden measurement need to be?

The nearest 10 cm is accurate enough for most garden jobs, as long as you round up rather than down when ordering. On a 10 m × 6 m lawn, overshooting each side by 10 cm gives 10.1 × 6.1 = 61.61 m², a difference of about 1.6 m². That is less than the 5% extra (3 m² here) that turf suppliers such as Rolawn recommend ordering anyway to cover trimming.

For a quick estimate before you fetch the tape, pace it out: walk 10 m with your normal stride to find your pace length, then count paces along each side. A measuring wheel is faster on long lawns and paths, but check it against a tape over a known distance first, because a wheel can slip on wet grass and under-read.

Common mistakes to avoid

Measuring fence to fence when you only need the lawn or the bed.
Mixing units, for example a length in metres and a width in feet.
Letting the tape sag or curve, which makes long sides read longer than they are.
Forgetting to subtract ponds, sheds, patios or beds inside the area.
Assuming opposite fences are parallel; measure both sides.

Frequently asked questions

How do I work out square metres of a garden?

Measure the length and width in metres and multiply them. For irregular gardens, split the area into rectangles, triangles and circles, calculate each one and add them together.

How many square feet is 100 square metres?

100 square metres is about 1,076 square feet, because one square metre equals 10.764 square feet.

How do I measure a garden with a curved border?

Lay a straight baseline, measure out to the curve at equal intervals, then multiply the spacing by the sum of the offsets, counting the first and last offsets as half.

Is the Land Registry plan accurate enough to measure my garden?

Not for precise work. Registered title plans normally show general boundaries, which do not fix the exact boundary line, so measure on the ground before ordering materials.

Should I measure a sloping lawn along the ground?

Yes, when buying turf, seed or membrane. A slope has more surface than its flat plan area, and measuring along the ground captures that extra.