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Turf calculator: turf rolls, seed, topsoil and bulk bags for a lawn
Measure the area, say what you are laying and find out how many rolls of turf or kilos of seed, tonnes and bulk bags of topsoil, or bags of MOT Type 1, gravel or bark to order. Turf, seed and topsoil follow Rolawn's figures: 1m² rolls with 5% for cuts, 35g of seed per m², 100 to 150mm of topsoil at 1.5 tonnes a cubic metre. Sub-base uses the same 2.1 tonnes per compacted m³ as the patio and hardcore calculators.
What you need
Lawn
- Area
- 50.0 m²
- Turf
- 53 × 1m² rolls5% for cuts round the edges. A roll is about 610 × 1640mm and 15 to 20kgRolawn Medallion: +5%
Topsoil
- Topsoil
- 8.6 tonnes100mm deep over 50m² is 5m³, plus 15% for settling, at 1.5 tonnes per m³Rolawn: 100–150mm; 1 tonne ≈ 0.67m³
- Topsoil bulk bags
- 12 × 0.5m³ bagsabout 800kg each; a bag does about 4m² at 100mmRolawn bulk bags: 0.5m³ standard, 0.75m³ large
- Or loose loads
- 1.2 × 7 tonne tipper
Sundries
- Pre-turf fertiliser
- 1 × 3.5kg boxesabout 35g per m² raked in before laying or sowing
- Edging
- 31.5 mround the perimeter, plus 5%
Round up to whole packs and bags. Figures include the wastage you chose and match TradeCalc in the app.
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Or claim your free profile link nowHow the maths works
- Turf comes in rolls of about 1m² (Rolawn Medallion is 610 × 1640mm). Rolls are the area plus 5% for a rectangle, which is what Rolawn adds, or 10% for curves and awkward shapes.
- Seed is 35g per m² for a new lawn, so 1kg does about 28m² (Rolawn Medallion seed); overseeding takes about 23g.
- A new lawn needs 100 to 150mm of topsoil to root into (Rolawn). That is the area × depth plus 15% for settling, at 1.5 tonnes per cubic metre (Rolawn: a tonne is about 0.67m³). Bags are counted by volume because that is how topsoil is sold: 0.5m³ standard, 0.75m³ large.
- MOT Type 1 is the compacted volume at 2.1 tonnes per m³ plus 10%, the same figure as the patio and hardcore calculators. There is no separate compaction factor: the density is already for the whacked layer.
- Gravel is the volume plus 5% at 1.7 tonnes per m³, in bulk bags of about 800kg. Bark is sold by volume, so it is counted in bags of about 0.75m³ rather than tonnes.
- Gravel and bark go on a weed membrane, in 10, 15 or 50m² rolls with 10% for overlaps and 4 pegs per m². Pre-turf fertiliser is about 35g per m², a 3.5kg box per 100m². Edging is the perimeter plus 5%.
Worked example
A 10m by 5m lawn is 50m². With 5% for cuts that is 53 rolls of turf. 100mm of topsoil underneath is 5m³, or 5.8m³ with settlement, which is 8.6 tonnes or 12 standard 0.5m³ bulk bags, plus 1 box of pre-turf fertiliser and 31.5m of edging.
Questions people ask
How many rolls of turf do I need?
One roll per square metre, plus 5% for cuts on a rectangle or 10% on curves. Measure the lawn, multiply length by width, and round up to whole rolls. A 50m² lawn needs about 53 rolls. Lay it the day it arrives.
How much topsoil do I need for a new lawn?
Rolawn says 100 to 150mm of topsoil for turf or seed. That is 0.1 to 0.15m³ per square metre before it settles; one tonne is about 0.67m³, so a 0.5m³ bag does about 4 to 5m² at 100mm. Borders want 150 to 200mm and vegetable beds 300 to 400mm.
How many square metres does a bulk bag cover?
Topsoil is sold by volume: a standard bag is 0.5m³ (about 800kg) and a large one 0.75m³, so about 10m² at 50mm or 5m² at 100mm. Gravel and Type 1 are sold by weight at about 800kg a bag, which is roughly 0.45m³ of gravel or 0.4m³ of compacted Type 1. Bark is much lighter and its bags are bigger.
Turf or seed?
Turf gives you a lawn in a day and can be laid most of the year if it is watered. Seed costs a fraction of the price, needs 35g per m² and a warm, damp spring or autumn to establish, and you keep off it for six to eight weeks. Both need the same 100 to 150mm of topsoil underneath.
What depth should gravel be?
40 to 50mm for a decorative path or bed on a membrane, so the ground does not show through. Driveways need a proper sub-base of MOT Type 1 at 100 to 150mm compacted underneath, which is a separate line here.
Is it cheaper to buy loose or in bulk bags?
Loose tipper loads are usually cheaper per tonne once you are over four or five bags, but you need somewhere to tip it. Prices vary by area and supplier, so get quotes for both.
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