What does lawn sand do?

Lawn sand contains ferrous sulphate (kills moss and greens grass) and sharp sand (improves drainage). It is a traditional spring lawn treatment.

When should I apply lawn sand?

Apply in April-May when grass is growing and moss is active. Apply on a dry day when rain is expected within 48 hours.

How quickly does lawn sand work?

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.

Can lawn sand burn grass?

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.

Is lawn sand safe for pets?

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.

GardenCalcs

Lawn Sand Calculator — Moss Control & Greening

Calculate lawn sand quantities for moss control and greening.

Lawn Area

Total grass area to treat — measure length × width and subtract beds and paths

Price per kg (optional)

A 16 kg Westland Lawn Sand bag (≈£15–20) works out around £1/kg — leave at 0 to skip costing

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

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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.