Topsoil Calculator — Tonnes & Cost

Topsoil quantity is calculated as area × depth, converted to tonnes. Loose topsoil has a bulk density of approximately 1.3–1.5 t/m³. For new lawns, a minimum depth of 100–150 mm of topsoil is recommended. Raised beds typically need 200–300 mm depth, and border improvement needs 50–100 mm mixed into existing soil.

Topsoil quality in the UK is graded to BS 3882. General-purpose topsoil suits most garden uses; premium topsoil is screened to a finer grade for lawns and turf laying. The calculator shows volume in cubic metres, weight in tonnes and number of bulk bags (a standard bulk bag of topsoil is approximately 0.6 m³ or 0.8–1.0 tonnes).

Enter the area and desired depth. The calculator shows quantity, estimated delivery cost (£30–£55 per tonne for general purpose, £45–£70 per tonne for premium screened) and the number of bulk bags. For large areas, loose-load delivery by tipper truck is more economical than bulk bags.

How much topsoil do you need? Volume = area × depth. Common scenarios: levelling lawn 50mm = 0.05 m³/m². Raised bed 200mm depth = 0.2 m³/m². New lawn over poor soil 100mm = 0.1 m³/m². Sample 50 m² lawn × 50mm = 2.5 m³ topsoil. Bulk bag (UK standard): 0.7-0.9 m³ — so 3 bulk bags. Bag weight ~875 kg (topsoil density 1.25 tonnes/m³). Loose tipper delivery (10+ m³): much cheaper per m³ but needs ⅓-acre access and somewhere to dump it.

UK topsoil grades and prices 2026. Screened general purpose: £35-£60/m³ delivered, BS3882-compliant. Premium topsoil (low-stone, low-clay): £60-£100/m³. Loam (free-draining mix): £55-£90/m³. Vegetable garden topsoil (high organic matter): £70-£120/m³. Sub-soil (cheaper but for bulk filling only, not planting): £20-£40/m³. Beware super-cheap 'topsoil' — often subsoil or contaminated waste. Always check supplier credentials and request soil analysis if buying in volume (10+ m³).

Reading soil — pH and texture. Send a sample to NRM Laboratories or RHS for £20-£40 analysis. UK common soils: clay (heavy, fertile, slow-draining, alkaline tendency); sandy (light, free-draining, low nutrients, acid tendency); loam (ideal balance); peat (acidic, water-retentive). pH targets: vegetables 6.0-7.0; lawn 5.5-7.0; ericaceous plants (rhododendrons, blueberries) 4.5-5.5. Lime to raise pH (calcified seaweed £15-£25/25kg); sulphur or pine needle mulch to lower pH.

Topsoil for raised beds — depth requirements. Vegetables: minimum 300mm depth, 400-450mm ideal for root crops (carrots, parsnips). Salad/herbs: 200mm sufficient. Fruit bushes: 400-500mm. Lawn over hard subsoil: 100-150mm minimum for healthy root growth. Standard 1.2m × 2.4m raised bed at 300mm = 0.86 m³ — about 1 bulk bag. Mix with 25% compost for richer growing medium. Top up annually (organic matter sinks/decomposes) — typically 25-50mm/year.

Topsoil sourcing — buy or move. If doing excavation work (foundations, basement, pond): you'll have surplus topsoil — keep top 200-300mm separately (this is the valuable layer). Subsoil below is useless for planting. Soil swap groups (Freecycle, Olio): free if you collect; sellers in same area can save delivery cost. Builder's merchants vs garden centres: garden centres charge 2-3× builder's merchant prices for bagged 'multi-purpose' topsoil. For >2 m³: always buy bulk bag or loose load from soil suppliers.