Mulch Calculator - Bark, Wood Chip & Compost
Calculate Mulch for UK Gardens & Landscaping
Whether you're mulching flower beds, creating bark paths, or improving soil with compost, this calculator helps you determine exactly how much material you need. Enter your area dimensions and select your mulch type to get accurate results in cubic metres, litres, and number of bags.
Mulching suppresses weeds, retains moisture, regulates soil temperature, and improves soil structure as organic mulches decompose. Apply in spring or autumn for best results.
Measure across the widest point of your circular bed
Tip: For irregular shapes, divide into rectangles, calculate each area, then add them together. Or use the formula: break into triangles where Area = ½ × base × height.
Why Mulch Your Garden? Key Benefits
Weed Suppression
A 50-75mm layer blocks light, preventing most annual weeds from germinating. Fewer weeds means less work and healthier plants that don't compete for nutrients.
Moisture Retention
Mulch reduces water evaporation by up to 70%, meaning less watering in summer. Essential during UK hosepipe bans and drought conditions.
Temperature Regulation
Insulates soil against temperature extremes - keeps roots cool in summer and protects from frost in winter. Extends the growing season.
Soil Improvement
Organic mulches decompose over time, adding humus and nutrients to soil. Encourages earthworms and beneficial soil organisms.
Aesthetic Appeal
Creates a neat, finished look to beds and borders. Hides bare soil and provides visual contrast with plants and flowers.
Erosion Prevention
Protects soil from heavy rain impact, preventing erosion on slopes and keeping nutrients in place rather than washing away.
Mulch Calculation Formulas
Rectangular Beds
Volume = L × W × D
L = Length, W = Width, D = Depth (all in metres)
Circular Beds
Volume = π × r² × D
r = radius (diameter ÷ 2), D = Depth
Worked Example - Rectangular Bed
Project: Mulching a border - 6m × 1.5m at 50mm depth
1. Calculate area: 6m × 1.5m = 9m²
2. Convert depth: 50mm ÷ 1000 = 0.05m
3. Calculate volume: 9m² × 0.05m = 0.45m³
4. Convert to litres: 0.45 × 1000 = 450 litres
5. Add 10% extra: 450 × 1.1 = 495 litres
6. Bags needed: 495 ÷ 60 = ~9 bags (60L bags)
Types of Mulch Available in the UK
| Mulch Type | Cost (60L bag) | Lifespan | Best For |
|---|---|---|---|
| Bark Mulch (Pine/Mixed) | £3-6 | 2-3 years | Flower beds, borders, shrubs. Good balance of appearance and function. |
| Wood Chip | £2-4 | 1-2 years | Large areas, woodland gardens, paths. Economical choice. |
| Composted Bark | £4-7 | 1-2 years | Beds where soil improvement is priority. Breaks down faster. |
| Garden Compost | £3-5 / Free | 6-12 months | Soil conditioning, vegetable gardens. Annual application needed. |
| Decorative Bark | £5-10 | 3-4 years | Front gardens, feature beds. Premium appearance, uniform chips. |
| Play Bark (BS EN 1177) | £5-8 | 2-3 years | Children's play areas. Safety certified for fall absorption. |
Recommended Mulch Depths
Flower Beds & Borders
50-75mm
Effective weed suppression while allowing water penetration. Keep mulch away from plant stems.
Trees & Shrubs
50-100mm
Create a "doughnut" shape - leave 75-100mm gap around trunk to prevent rot.
Bark Paths
75-100mm
Use chunky bark for durability. Consider edging to prevent spreading. Top up annually.
Play Areas
150-300mm
Use BS EN 1177 certified play bark. 200mm minimum for 1.5m fall height. Check depth regularly.
Important Mulching Tips
- Don't "volcano mulch" - never pile mulch against tree trunks or plant stems as this causes rot
- Weed first - remove all weeds before mulching, especially perennials like bindweed
- Water before mulching - apply to moist (not wet) soil for best results
- Avoid fresh wood chip on beds - it temporarily depletes nitrogen as it decomposes
- Refresh don't replace - top up annually rather than complete replacement
Mulch Coverage Quick Reference
Use this table to estimate how much area you can cover with different quantities of mulch.
| Mulch Quantity | @ 50mm Depth | @ 75mm Depth | @ 100mm Depth |
|---|---|---|---|
| 1 bag (60L) | 1.2m² | 0.8m² | 0.6m² |
| 5 bags (300L) | 6m² | 4m² | 3m² |
| 10 bags (600L) | 12m² | 8m² | 6m² |
| 1m³ (bulk) | 20m² | 13.3m² | 10m² |
| Bulk bag (850L) | 17m² | 11.3m² | 8.5m² |
UK Mulch Prices 2024-2025
Prices vary by quality, brand, and quantity. Buying in bulk significantly reduces cost per litre.
Bagged (60L)
Bark: £3-6
Wood chip: £2-4
Decorative: £5-10
Bulk Bag (850L)
Bark: £45-80
Wood chip: £30-50
Decorative: £60-100
Loose (per m³)
Bark: £40-70
Wood chip: £25-50
Compost: £30-60
Delivery
Bulk bags: £30-60
Loose loads: £40-80
Often free over £100
Money-Saving Tips
- Council green waste: Many councils sell composted green waste for £20-40/tonne
- Tree surgeons: Often give away wood chip for free - check local Facebook groups
- Bulk is cheaper: 1m³ bulk costs less than 17 × 60L bags (same volume)
- Multi-buy offers: Garden centres often discount 3+ bags
- Share delivery: Split a bulk order with neighbours
Best Time to Mulch in the UK
Spring (April-May)
Benefits: Retains moisture for summer, soil has warmed up, weeds haven't established
Best for: All beds after clearing spring weeds
Autumn (October-November)
Benefits: Protects roots from frost, breaks down over winter adding nutrients
Best for: Perennials, new plantings, soil improvement
When NOT to Mulch
- Frozen ground: Don't mulch when soil is frozen - it traps cold
- Waterlogged soil: Wait until drainage improves
- Very dry soil: Water thoroughly before mulching
- Weed-infested beds: Clear weeds first or you'll make problems worse
Where to Buy Mulch in the UK
Garden Centres
- Dobbies
- Squire's
- Wyevale/Blue Diamond
- British Garden Centres
- Local independent centres
DIY Stores
- B&Q
- Homebase
- Wickes
- Wilko
- The Range
Bulk Suppliers
- Local landscape suppliers
- Melcourt Industries
- Rolawn
- Gravelmaster
- Builders' merchants
Free/Cheap Sources
- Council recycling centres
- Local tree surgeons
- Arborists/landscapers
- Facebook Marketplace
- Community composting schemes
Frequently Asked Questions
How much mulch do I need for my garden?
+To calculate mulch needed: Length (m) × Width (m) × Depth (m) = Volume in cubic metres. For a standard 50mm depth, you need approximately 0.05m³ (50 litres) per square metre. For example, a 10m² flower bed at 50mm depth needs 0.5m³ or 500 litres of mulch. Most bagged mulch comes in 50-60L bags, so you'd need 8-10 bags. Add 10% extra for settling and irregular edges.
How deep should mulch be for garden beds in the UK?
+Recommended mulch depths: 50-75mm (2-3 inches) for flower beds and borders to suppress weeds and retain moisture. 75-100mm (3-4 inches) for bark paths and play areas. 25-50mm (1-2 inches) around established trees and shrubs (keeping mulch away from the trunk). For compost as a soil improver, apply 50mm in autumn. Deeper layers are more effective at weed suppression but require more material.
What is the best type of mulch for UK gardens?
+The best mulch depends on your purpose: Bark mulch is excellent for weed suppression and moisture retention, lasting 2-3 years. Wood chip is economical for large areas. Composted bark improves soil as it breaks down. Garden compost enriches soil but needs annual replacement. For most UK flower beds, medium-grade bark mulch offers the best balance of appearance, function, and value.
How much does mulch cost in the UK in 2024-2025?
+UK mulch prices in 2024-2025: Bark mulch costs £3-6 per 60L bag, or £40-70 per cubic metre bulk. Wood chip is cheaper at £2-4 per 60L bag, or £25-50 per cubic metre bulk. Decorative bark costs £5-10 per 60L bag. Bulk delivery typically adds £30-60. Council recycling centres often offer free or cheap composted green waste.
When is the best time to apply mulch in the UK?
+The best times to mulch in the UK are late spring (April-May) after soil has warmed up but before summer drought, or autumn (October-November) after clearing beds and before winter. Avoid mulching in winter when soil is frozen or waterlogged. Spring mulching helps retain moisture for summer; autumn mulching protects roots from frost. Always weed thoroughly before applying mulch.
Does mulch attract slugs and other pests?
+Yes, organic mulches can provide habitat for slugs, snails, and woodlice due to the moisture they retain. To minimise problems: use coarser bark chips rather than fine mulch, keep mulch 50-75mm away from plant stems, apply slug pellets or use nematodes in spring, and consider gravel mulch for slug-prone areas around vulnerable plants like hostas. The benefits generally outweigh this concern.
How long does bark mulch last before needing replacement?
+Bark mulch typically lasts 2-3 years before needing replacement or topping up. Fine bark breaks down faster (1-2 years), while chunky bark lasts longer (3-4 years). Factors affecting longevity include bark grade, climate, soil organisms, and sunlight exposure. Rather than full replacement, most gardeners top up annually with 25-50mm of fresh mulch to maintain depth and appearance.
Should I use landscape fabric under mulch?
+Landscape fabric under mulch is optional. Pros: provides extra weed barrier, mulch stays cleaner. Cons: prevents organic matter improving soil, can tear and look untidy, makes planting difficult. For permanent bark paths or around established shrubs, fabric works well. For flower beds where you plant regularly, skip the fabric - the mulch alone suppresses most weeds while improving soil as it decomposes.
Last Updated: December 2025 | Prices and coverage rates based on UK market data
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