Soil & Compost Calculators

Soil is the most important resource in any UK garden, and understanding what you have and what you need to add makes the difference between struggling plants and abundant growth. The UK has an enormous variety of soil types — from heavy London clay and Midlands marl to chalky downland soils and sandy East Anglian loams. Our soil amendment calculator helps you work out how much grit, sharp sand, or organic matter to incorporate for improving drainage or water retention. The soil pH adjustment calculator is particularly useful, as UK soils range from very acidic (pH 4.5 on peaty moorland) to highly alkaline (pH 8+ on chalk), and many popular plants like rhododendrons, blueberries, and camellias need acidic conditions below pH 6.

Raised beds have become enormously popular in UK gardens and allotments, especially where the existing soil is poor or contaminated. Our raised bed soil calculator works out how many cubic metres or bulk bags of topsoil you need to fill beds of any dimension. Standard raised beds are typically 1.2m wide (so you can reach the centre from either side) and 30-45cm deep. The topsoil calculator covers larger projects and provides quantities in bulk bags, which typically contain 0.75-0.85 cubic metres and weigh roughly a tonne.

Home composting is strongly encouraged by UK local councils, many of which offer subsidised compost bins. Our compost bin size calculator helps you choose the right capacity for your household and garden waste, while the green to brown ratio calculator ensures you maintain the ideal 25:1 to 30:1 carbon-to-nitrogen ratio for efficient decomposition. For autumn leaf collection, the leaf mould calculator estimates how much rich, crumbly leaf mould you will produce after 12-18 months of decomposition — one of the best free soil conditioners available to British gardeners.