For a round bed or island. Leave at 0 if not needed.
Driveway, patio, shed footprint — anything inside the measurement that is not lawn.
Quantity estimate for planning and buying. Rates vary by variety, region and product — check the label on what you actually buy.
How do you measure an irregular lawn?
Break the lawn into rectangles, circles and triangles, work out each shape separately, add them together, then subtract the patio, beds, shed and driveway that sit inside the boundary you measured.
The three formulas are all you need: rectangle is length × width, circle is π × radius² (measure across the widest point and halve it), and triangle is base × height ÷ 2 with the height measured square to the base, not along a sloping side.
For a genuinely curved border, run a straight line through the middle of the curve so the bulges and hollows cancel. Pacing is accurate enough — most adults have a pace close to 2.5 ft, which gets you within a few per cent, comfortably inside the waste allowance on every product you are about to buy.
How to measure an awkward lawn
Every seed, fertilizer and sod calculation starts with an area, and an area you guessed at makes everything downstream a guess. The reliable method is to break the lawn into shapes you can measure, work out each one, then add:
- Rectangle: length × width.
- Circle: π × radius² — measure across the widest point and halve it.
- Triangle: base × height ÷ 2, where the height is measured square to the base, not along a sloping side.
For a genuinely curved border, the practical trick is to treat the curve as a straight line through its middle — averaging the bulges against the hollows. Over a whole lawn the errors largely cancel out.
Subtract what is not lawn
This is where money leaks. If you measure the whole back garden and it contains a 300 ft² patio, a shed and two beds, you will buy seed and fertilizer for 300-plus square feet of paving. Measure those and subtract them.
Pacing is accurate enough for this. Walk a known distance, count your paces, and work out your pace length — most adults are close to 2.5 ft. Pacing a lawn boundary gets you within a few per cent, which is inside the waste allowance on every product you are about to buy.
| Unit | Square feet | Square metres |
|---|---|---|
| 1,000 ft² (the lawn-product unit) | 1,000 | 92.9 |
| 1 acre | 43,560 | 4,047 |
| 1/4 acre lot | 10,890 | 1,012 |
| 1/8 acre lot | 5,445 | 506 |
| 1 square (10 x 10 ft) | 100 | 9.29 |
| 1 square metre | 10.76 | 1 |
Common questions
How do I calculate the square footage of an irregular lawn?
Break it into rectangles, circles and triangles, calculate each, add them, then subtract patios, beds and driveways inside the measured boundary.
How many square feet are in an acre?
43,560 ft². A quarter-acre lot is 10,890 ft², though the lawn itself is usually far less once the house, drive and beds come out.
How accurate does my lawn measurement need to be?
Within about 10%. Every product you buy has a waste or coverage allowance wider than that, and bags come in fixed sizes anyway. Pacing the boundary is accurate enough.