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Soil Calculator 2026 | Topsoil & Compost Volume Calculator UK

Soil Calculator 2026

Calculate Topsoil, Compost & Garden Soil Requirements

Professional Soil Volume & Quantity Calculator UK

Accurate soil calculation ensures optimal plant growth, proper drainage, and cost-effective landscaping projects. Our soil calculator determines the exact volume of topsoil, compost, mulch, or growing medium needed for lawns, raised beds, borders, and landscaping applications. Calculate requirements in cubic meters, tonnes, or bags based on RHS soil standards and professional horticultural guidelines.

Understanding soil depth requirements, bulk density, and material properties prevents over-ordering and ensures adequate coverage. Our calculator accounts for settlement, compaction, and application-specific depth recommendations following DEFRA construction codes and UK gardening best practices for 2026.

🌱 Soil & Topsoil Calculator

Calculate required soil volume, weight, and quantity

Project Details

Area & Depth

Soil Depth Requirements 2026

Proper soil depth ensures healthy root development, adequate drainage, and successful plant establishment. Our soil calculator uses RHS and horticultural guidelines to recommend appropriate depths for different applications.

Recommended Soil Depths by Application

Application Minimum Depth Recommended Depth Notes
New Lawn Preparation 100mm 150-200mm Good quality topsoil, level and firm
Lawn Top Dressing 15mm 25-50mm Fine grade, work into existing grass
Flower/Shrub Borders 150mm 200-300mm Mix with compost for nutrients
Vegetable Garden 200mm 300-450mm Deep rooting crops need more depth
Raised Beds 200mm 300-600mm Higher for root vegetables
Container/Planter Fill 150mm 300-450mm Use quality compost blend
Mulch/Bark Layer 50mm 75-100mm Weed suppression and moisture retention
Tree Planting Pit 450mm 600-900mm 1.5-2x root ball diameter
Green Roof (Extensive) 80mm 100-150mm Lightweight substrate required
Green Roof (Intensive) 200mm 300-600mm Structural assessment needed

New Lawn Preparation

Minimum Depth 100mm
Recommended 150-200mm
Notes Quality topsoil

Vegetable Garden

Minimum Depth 200mm
Recommended 300-450mm
Notes Deep cultivation

Raised Beds

Minimum Depth 200mm
Recommended 300-600mm
Notes Higher for roots

Mulch/Bark Layer

Minimum Depth 50mm
Recommended 75-100mm
Notes Weed suppression

Soil & Material Types

Different soil types and growing media suit specific applications. Our soil calculator accounts for bulk density variations to provide accurate weight and volume calculations for delivery and handling.

General Purpose Topsoil

Bulk Density: 1,200-1,400 kg/m³

Cost: £30-50 per tonne / £35-60 per m³

Applications: Lawns, borders, general landscaping

Characteristics: Natural soil, may contain stones

Best For: Large areas, ground leveling, bulk projects

Premium Screened Topsoil

Bulk Density: 1,100-1,300 kg/m³

Cost: £50-80 per tonne / £60-100 per m³

Applications: Quality lawns, fine gardens

Characteristics: Stone-free, consistent texture

Best For: High-quality lawn establishment, show gardens

Multi-Purpose Compost

Bulk Density: 600-800 kg/m³

Cost: £80-120 per m³ / £3-6 per 40L bag

Applications: Containers, planters, raised beds

Characteristics: Nutrient-rich, lightweight

Best For: Potting, seed sowing, container gardening

Peat-Free Compost

Bulk Density: 650-850 kg/m³

Cost: £90-140 per m³ / £4-7 per 40L bag

Applications: Eco-friendly gardening, all uses

Characteristics: Sustainable, coir/wood fiber based

Best For: Environmentally conscious gardening

Well-Rotted Manure

Bulk Density: 800-1,000 kg/m³

Cost: £40-70 per tonne / £50-90 per m³

Applications: Soil conditioning, vegetable gardens

Characteristics: High organic matter, nutrient-rich

Best For: Soil improvement, vegetable cultivation

Bark Mulch/Wood Chip

Bulk Density: 400-600 kg/m³

Cost: £30-60 per m³ / £50-90 per tonne

Applications: Surface mulch, path covering

Characteristics: Lightweight, decorative

Best For: Weed suppression, moisture retention

Sharp Sand/Horticultural Sand

Bulk Density: 1,600-1,800 kg/m³

Cost: £40-60 per tonne / £60-100 per m³

Applications: Soil conditioning, lawn dressing

Characteristics: Improves drainage, heavy

Best For: Clay soil improvement, sand-based lawns

Turf Dressing/Lawn Soil

Bulk Density: 1,300-1,500 kg/m³

Cost: £60-100 per tonne / £80-140 per m³

Applications: Lawn top dressing, leveling

Characteristics: Fine grade, sand/loam mix

Best For: Lawn maintenance, surface leveling

Bulk Density & Weight Calculations

Understanding bulk density is essential for accurate ordering. Soil is typically sold by weight (tonnes) or volume (cubic meters). Our soil calculator converts between these measurements based on material-specific bulk densities.

📐 Soil Calculation Formulas:

  • Volume (m³): Length (m) × Width (m) × Depth (m)
  • Weight (tonnes): Volume (m³) × Bulk Density (kg/m³) ÷ 1000
  • With Settlement: Base Volume × (1 + Settlement %)
  • Example: 10m × 5m × 0.15m = 7.5m³ → 7.5 × 1.3 (topsoil) = 9.75 tonnes
  • Bags (40L): Volume (m³) × 1000 ÷ 40 = Number of bags

Bulk Density Reference Guide

Material Bulk Density (kg/m³) Weight per m³ Volume per Tonne
General Topsoil 1,300 1.3 tonnes 0.77 m³
Screened Topsoil 1,200 1.2 tonnes 0.83 m³
Clay Soil 1,600 1.6 tonnes 0.63 m³
Sandy Soil 1,500 1.5 tonnes 0.67 m³
Compost 700 0.7 tonnes 1.43 m³
Manure (Rotted) 900 0.9 tonnes 1.11 m³
Bark Mulch 500 0.5 tonnes 2.00 m³
Sharp Sand 1,700 1.7 tonnes 0.59 m³
Turf Dressing 1,400 1.4 tonnes 0.71 m³

General Topsoil

Bulk Density 1,300 kg/m³
Weight per m³ 1.3 tonnes
Volume per Tonne 0.77 m³

Compost

Bulk Density 700 kg/m³
Weight per m³ 0.7 tonnes
Volume per Tonne 1.43 m³

Bark Mulch

Bulk Density 500 kg/m³
Weight per m³ 0.5 tonnes
Volume per Tonne 2.00 m³

Sharp Sand

Bulk Density 1,700 kg/m³
Weight per m³ 1.7 tonnes
Volume per Tonne 0.59 m³

Purchase Options & Packaging

Soil and compost are available in various package sizes. Our calculator provides quantities for all common formats to help you choose the most cost-effective option for your project size.

Standard Bags (40-50L)

Volume: 0.04-0.05 m³ per bag

Coverage: 0.25-0.33 m² at 150mm depth

Cost: £3-7 per bag (material dependent)

Best For: Small projects, containers, top-ups

Availability: Garden centers, DIY stores

Delivery: Car/van transportable

Large Bags (70-80L)

Volume: 0.07-0.08 m³ per bag

Coverage: 0.47-0.53 m² at 150mm depth

Cost: £5-12 per bag

Best For: Medium projects, raised beds

Availability: Garden centers, landscaping suppliers

Delivery: Multiple bags car/van transportable

Bulk Bags (1m³ / 1000L)

Volume: 0.9-1.0 m³ per bag (settled)

Coverage: 6-7 m² at 150mm depth

Cost: £35-140 per bag (material dependent)

Best For: Large projects, best value for volume

Availability: Landscaping/builder merchants

Delivery: Crane/forklift unloading required

Loose Load (Tipper Lorry)

Volume: 10-20 tonnes typical load

Coverage: 60-150 m² at 150mm depth

Cost: £30-80 per tonne delivered

Best For: Very large projects, most economical

Availability: Bulk soil suppliers, quarries

Delivery: Access for large vehicle required

Cost Comparison 2026

Soil and compost costs vary significantly by material type, quality, and purchase quantity. Bulk buying typically offers 40-60% savings compared to bagged products. Factor in delivery costs when comparing suppliers.

Material Bagged (per m³) Bulk Bag (per m³) Loose Load (per m³) Best Value
General Topsoil £120-160 £45-65 £35-50 Loose load
Premium Topsoil £180-250 £70-100 £55-80 Bulk bag/Loose
Multi-Purpose Compost £160-200 £90-130 £80-120 Bulk bag
Peat-Free Compost £180-240 £100-150 £90-140 Bulk bag/Loose
Well-Rotted Manure £140-190 £55-85 £45-70 Loose load
Bark Mulch £180-260 £45-75 £35-60 Loose load
Sharp Sand £150-200 £65-95 £50-75 Loose load
Turf Dressing £200-280 £85-125 £70-105 Bulk bag

General Topsoil

Bagged £120-160/m³
Bulk Bag £45-65/m³
Loose Load £35-50/m³
Best Value Loose load

Multi-Purpose Compost

Bagged £160-200/m³
Bulk Bag £90-130/m³
Loose Load £80-120/m³
Best Value Bulk bag

Bark Mulch

Bagged £180-260/m³
Bulk Bag £45-75/m³
Loose Load £35-60/m³
Best Value Loose load

Turf Dressing

Bagged £200-280/m³
Bulk Bag £85-125/m³
Loose Load £70-105/m³
Best Value Bulk bag

✅ Cost Savings Tips:

  • Buy in Bulk: Bulk bags save 50-70% vs bagged, loose loads save up to 75%
  • Combine Orders: Share delivery with neighbors to split fixed delivery costs
  • Seasonal Timing: Order in autumn/winter when demand is lower (10-20% savings)
  • Local Suppliers: Reduce delivery distance - transportation can add £50-150
  • Compare Quotes: Prices vary significantly between suppliers (30%+ difference)
  • Accept Delivery Windows: Flexible delivery dates often receive discounts
  • Consider Quality: Premium soil costs more but performs better long-term

Soil Quality Standards

Quality topsoil should meet BS 3882:2015 specifications for composition, contamination levels, and suitability. Always request certification for commercial projects and verify material before acceptance.

⚠️ Quality Checks Before Ordering:

  • BS 3882 Certification: Ensure supplier provides certified topsoil meeting British Standards
  • Visual Inspection: Check sample for stones, debris, weeds, and contamination
  • pH Testing: Most plants prefer pH 6.0-7.5; test before ordering large quantities
  • Organic Content: Good topsoil contains 3-10% organic matter for fertility
  • Texture Test: Squeeze moist soil - should form ball but crumble easily (loam texture)
  • Smell Check: Should smell earthy; avoid sour/chemical odors indicating contamination
  • Supplier Reputation: Check reviews, ask for references from previous customers
  • Source Verification: Know where soil originated - avoid contaminated/urban sites

Soil Improvement & Conditioning

Existing soil often benefits from amendment rather than complete replacement. Mix compost, manure, or sand to improve structure, drainage, and fertility at lower cost than importing fresh topsoil.

Soil Improvement Ratios

Existing Soil Type Problem Amendment Ratio (by volume)
Heavy Clay Poor drainage, compaction Sharp sand + compost 1:1:1 (soil:sand:compost)
Light Sandy Poor water retention, low nutrients Compost + manure 3:1 (soil:compost/manure)
Chalky/Alkaline High pH, nutrient lockup Ericaceous compost + sulfur 2:1 (soil:ericaceous)
Acidic/Peaty Low pH, waterlogged Lime + grit Add 200g lime per m²
Low Fertility Poor plant growth, pale foliage Well-rotted manure 10-15 kg per m²
Compacted/Hard Poor root penetration Compost + mechanical aeration 50mm layer worked in

Heavy Clay Soil

Problem Poor drainage
Amendment Sand + compost
Ratio 1:1:1 mix

Light Sandy Soil

Problem Poor water retention
Amendment Compost + manure
Ratio 3:1 mix

Low Fertility Soil

Problem Poor growth
Amendment Rotted manure
Ratio 10-15 kg/m²

Compacted Soil

Problem Poor penetration
Amendment Compost + aerate
Ratio 50mm layer

Soil Calculator FAQs

How much topsoil do I need for a new lawn?
For a quality new lawn, you need minimum 100mm (preferably 150-200mm) of good quality topsoil. Calculate: Area (m²) × Depth (m) = Volume (m³). Example: 50m² lawn × 0.15m depth = 7.5m³ topsoil. Add 10% for settlement = 8.25m³ total. At 1.3 tonnes/m³ = approximately 11 tonnes of topsoil.
Is it cheaper to buy soil in bags or bulk?
Bulk is significantly cheaper. Bagged topsoil costs £120-160 per m³, bulk bags cost £45-65 per m³ (60% savings), and loose loads cost £35-50 per m³ (70% savings). For projects needing more than 1-2m³, bulk delivery is most economical despite £50-100 delivery charge. Small projects under 0.5m³ may find bags more practical.
How many 40L bags equal 1 cubic meter?
One cubic meter (1m³) equals 1,000 liters. Therefore: 1m³ = 25 bags of 40L compost, or approximately 14 bags of 70L compost. For topsoil (which compacts more), expect 22-23 bags per m³. Our calculator provides exact bag quantities for your specific volume requirements and material type.
What depth of topsoil do I need for vegetable growing?
Vegetable gardens need 200mm minimum depth, but 300-450mm is ideal for deep-rooting crops like carrots, parsnips, and potatoes. Salad crops and herbs can manage with 150mm. Raised beds should be 300-600mm deep. Better depth = better drainage, root development, and yields. Mix topsoil 50:50 with compost for optimal vegetable growing.
Should I use topsoil or compost for raised beds?
Use a mix of both. Ideal raised bed mix: 50% quality topsoil, 40% compost, 10% sharp sand or perlite. Pure compost is too light and dries quickly; pure topsoil may lack nutrients and drainage. The blend provides structure (topsoil), nutrients (compost), and drainage (sand). For deep beds over 450mm, use cheaper topsoil in bottom third.
How do I calculate soil weight from volume?
Multiply volume (m³) by bulk density (kg/m³), then divide by 1,000 for tonnes. Topsoil density = 1,200-1,400 kg/m³ (average 1,300). Example: 5m³ × 1,300 kg/m³ = 6,500 kg = 6.5 tonnes. Compost is lighter (700 kg/m³), sand is heavier (1,700 kg/m³). Our calculator automatically converts volume to weight for accurate ordering.
What is BS 3882 certified topsoil?
BS 3882:2015 is the British Standard for topsoil quality, specifying composition, contamination limits, and grading. Certified topsoil is tested for: stone content, organic matter, pH, nutrients, and contaminants. Three grades exist: Premium (best), General Purpose, and Economy. Always request BS 3882 certification for landscape projects - it guarantees consistent, safe, quality soil.
Can I use subsoil instead of topsoil to save money?
No - subsoil lacks organic matter, nutrients, and microbial life essential for plant growth. It's suitable only for ground leveling, filling, or beneath topsoil layers. Plants grown in subsoil show poor growth, yellowing, and susceptibility to disease. For growing areas, always use proper topsoil. Subsoil costs £15-25/tonne vs £35-50/tonne for topsoil - the saving isn't worth failed plants.
How long does delivered topsoil last in storage?
Store topsoil properly and it lasts 2-3 months. Cover with tarpaulin to prevent weed seeds germinating and nutrient leaching from rain. Keep off concrete (can stain) and ensure drainage beneath pile. Compost degrades faster - use within 4-6 weeks. In sealed bags, materials last 6-12 months if kept dry. For best results, spread soil promptly after delivery.
What's the difference between topsoil and loam?
Topsoil is the natural upper soil layer; loam is a specific soil texture (40% sand, 40% silt, 20% clay) - the ideal growing medium. Most "topsoil" sold isn't true loam. Premium topsoil products often blend screened soil with compost to create loam-like texture. True loam costs more (£60-100/m³) but provides optimal drainage, nutrients, and structure. For most gardens, good quality general topsoil is adequate.

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