GardenCalcs.uk
Top Dressing Calculator — Lawn Levelling Mix
Calculate how much top dressing mix to level and improve your lawn.
Measure the lawn's length × width in metres; subtract beds, paths and patios.
Light dressing 3-5 mm; up to 10 mm only when levelling — never bury the grass tips, brush it down between the blades.
Standard 70/20/10 suits most lawns; Sandy adds drainage on heavy clay; Rich adds organic matter for sandy, hungry soils.
Adds a margin for uneven spreading and material lost when brushing in — leave on unless you are ordering loose by volume.
Extra material to account for waste and spillage
How We Calculate This
Volume = Area × Depth (converted to metres). Depth is usually expressed in mm for top dressing.
The mix ratios are: Standard (70% sand, 20% loam, 10% compost), Sandy (80/10/10), Rich (50/30/20).
Bag count assumes the standard UK 25 kg bag. A sand/loam top dressing has a bulk density of about 1.6 kg per litre, so each 25 kg bag holds roughly 15.6 litres — the calculator divides the required volume by this, not by 25.
Frequently Asked Questions
Apply 5-10 mm at a time. For severely uneven lawns, repeat every 4-6 weeks during the growing season. Never bury the grass completely.
A standard mix is 70% sharp sand, 20% loam, and 10% peat-free compost. Match the mix to your soil type — sandy soils need more loam.
Top dress in autumn (September-October) or spring (April-May) when grass is actively growing. Avoid summer heat and winter dormancy.
Yes. Scarify first to remove thatch, then overseed if needed, then apply top dressing. This is the ideal autumn lawn renovation sequence.
September to October is ideal in the UK. The soil is warm, rain helps settle the dressing, and grass is actively growing to recover quickly.
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Last updated: February 2026
All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.