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Lawn Sand Calculator — Moss Control & Greening
Calculate lawn sand quantities for moss control and greening.
Total grass area to treat — measure length × width and subtract beds and paths
A 16 kg Westland Lawn Sand bag (≈£15–20) works out around £1/kg — leave at 0 to skip costing
70 g/m² is the traditional equal-parts recipe; Westland and most branded sands quote 80 g/m². Higher-iron (2% Fe) products go up to 125–150 g/m²
16 kg is the common UK retail bag (covers ~200 m²); 20 kg and small 4 kg tubs also sold
How We Calculate This
The traditional equal-parts lawn sand recipe spreads at about 70 g/m², while branded products such as Westland quote 80 g/m² (a 16 kg bag covers ~200 m²). Higher-iron sands (2% Fe) go up to 125–150 g/m² — always check your specific product label and adjust the Application Rate in Advanced Options.
Formula: Total (kg) = Area (m²) × Rate (g/m²) ÷ 1000. Bags = Total ÷ bag size, rounded up.
Frequently Asked Questions
Lawn sand contains ferrous sulphate (kills moss and greens grass) and sharp sand (improves drainage). It is a traditional spring lawn treatment.
Apply in April-May when grass is growing and moss is active. Apply on a dry day when rain is expected within 48 hours.
Moss starts blackening within a few days. Rake out dead moss after 10-14 days. The greening effect on grass is visible within a week.
Yes, if over-applied or used in hot, dry conditions. Stick to recommended rates and water in if rain does not arrive within 2 days.
Keep pets off treated areas for 2-3 days or until rain has washed the product into the soil. The iron sulphate in lawn sand can stain paws and is mildly irritating.
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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.