Mulch Calculator

How Much Mulch Do I Need?

This free mulch calculator works out exactly how much mulch you need for any garden bed, border or landscaping project. It works for bark mulch, composted bark, wood chip, decorative bark and other organic mulches. Choose your area shape — rectangular, circular or irregular — enter the dimensions and depth, and get an instant answer in cubic metres, litres, bag counts and approximate weight.

Planning a path or play area with bark chippings? Use our dedicated bark chippings calculator instead — it includes BS EN 1177 play bark safety depths and project-specific recommendations.

How to Calculate Mulch by Hand

The formula is straightforward: Length (m) × Width (m) × Depth (m) = Volume (m³). Multiply the volume by 1,000 to convert to litres, then divide by your bag size to get the number of bags.

The key mistake most gardeners make is entering depth in centimetres instead of metres. A 75mm layer is 0.075 metres — not 75. The calculator above handles this conversion for you, but if you are working it out manually, always divide your depth in centimetres by 100 first.

Worked Example: Standard Garden Border

A typical UK garden border measuring 4m long × 1.5m wide, mulched to 75mm (7.5cm) deep:

• Area: 4 × 1.5 = 6 m²
• Volume: 6 × 0.075 = 0.45 m³
• Litres: 0.45 × 1,000 = 450 litres
• 60L bags: 450 ÷ 60 = 8 bags
• 80L bags: 450 ÷ 80 = 6 bags
• 100L bags: 450 ÷ 100 = 5 bags

At roughly £5–£8 per 80L bag from a garden centre, that is £30–£48 for a single border. For larger areas, a bulk bag (1m³ / 1,000L) at £60–£90 delivered is far better value.

Worked Example: Front Garden Bed

A smaller front garden bed measuring 3m × 2m at 50mm (5cm) deep — the minimum depth for effective weed suppression:

• Area: 3 × 2 = 6 m²
• Volume: 6 × 0.05 = 0.30 m³
• Litres: 300 litres
• 80L bags: 300 ÷ 80 = 4 bags

Worked Example: Circular Tree Ring

Mulching around a tree with a 1.5m radius circle at 75mm deep:

• Area: π × 1.5² = 7.07 m²
• Volume: 7.07 × 0.075 = 0.53 m³
• Litres: 530 litres
• 80L bags: 530 ÷ 80 = 7 bags

Keep bark mulch at least 10cm away from the tree trunk to prevent moisture trapping and bark rot.

Quick Reference: Mulch Per Square Metre

Bags vs Bulk: Which Is Cheaper?

For areas under 5m², bagged bark from a garden centre or Amazon is the simplest option. But once you need more than about 500 litres (roughly half a cubic metre), bulk bags are significantly cheaper.

A typical price comparison for bark mulch in 2026:

• 80L bags: £5–£8 each (6–10p per litre)
• Bulk bag (1m³): £60–£90 delivered (6–9p per litre)
• Loose delivery (3–5m³): £40–£60 per m³ (4–6p per litre)

For larger projects — driveways, entire garden borders, or play areas — loose delivery by tipper truck gives the best price per litre. Most landscape suppliers offer this with minimum orders of 2–3 cubic metres.

Preparing your beds at the same time? Try our compost calculator for raised beds and borders, or our soil calculator if you need topsoil too.

Mulching before planting season? Our monthly vegetable growing calendar shows exactly when to sow seeds and plant out across the UK.

Recommended Mulch Depths by Type

Different mulch types work best at different depths. Use this guide to choose the right depth for your project.

Frequently Asked Questions

How Many Bags of Bark Mulch Do I Need?

Use this quick-reference table to estimate how many bags of bark mulch you need based on your area size. All figures assume a standard 50mm (5cm) mulching depth — the most common depth for beds and borders.

How much bark per square metre? At 50mm depth, you need 50 litres of bark mulch per square metre. At 75mm depth (better for weed suppression), you need 75 litres per square metre. The calculator above adjusts for your exact depth and area shape.

Tip: For areas over 10m², bulk bags (approximately 1,000 litres / 1m³) are significantly cheaper per litre than smaller bags. Most suppliers deliver bulk bags on a pallet.

Types of Garden Mulch Explained

Not all bark is the same. Choosing the right type for your project saves money and gives better results. Here is what each type is, where to use it, and how much you need.

Bark Mulch (10–40mm)

The most popular garden mulch in the UK. Bark mulch comes in chunky pieces of softwood or hardwood bark, typically graded by size. It suppresses weeds, retains soil moisture, and looks tidy for 2–3 years before needing a top-up. Apply at 50–75mm deep for borders, beds, and around trees. A 10m² area needs roughly 500–750 litres depending on depth. For bark chippings for paths and play areas, see our bark chippings calculator.

Composted Bark (Fine Grade)

Bark that has been composted and broken down into finer particles (5–15mm). It enriches the soil as it decomposes — making it the best choice for flower beds and borders where you want to improve soil structure over time. Needs replacing annually as it breaks down faster than chippings. Apply at 50mm deep. Our compost calculator can also help with composted bark quantities for raised beds.

Ornamental Bark (Decorative Grade)

Graded and screened for appearance, ornamental bark is the premium option for front gardens, borders visible from the house, and formal planting areas. Usually larger nuggets (20–40mm) with consistent colour. Costs more per bag but looks significantly better than standard bark chippings. Apply at 50–75mm deep over a weed membrane for the cleanest finish.

Play Bark (Play-Grade)

Specially graded bark for children's play areas. Must be free from sharp splinters and meet safety standards for impact absorption. Apply at a minimum of 200–300mm deep depending on the height of play equipment. See the play bark section below for detailed safety guidance and depth requirements.

Wood Chip

Whole-tree wood chip includes white wood as well as bark. It is the cheapest option but decomposes faster (12–18 months) and can temporarily deplete nitrogen from the soil surface. Best for informal paths, utility areas, and large-scale landscaping where appearance is less important. Apply at 75–100mm deep.

Play Bark for Children's Play Areas

If you are covering a children's play area, the depth of bark is a safety requirement — not just a preference. Play bark must absorb impact from falls, and the required depth depends on the height of the play equipment.

BS EN 1177 Depth Requirements

The UK standard for playground surfacing (BS EN 1177) specifies minimum depths based on the Critical Fall Height (CFH) of the equipment:

Important: Standard bark chippings do not meet play area safety standards. You must use play-grade bark that is certified to BS EN 1176/1177. Play bark is specifically graded to be free from sharp edges and splinters, and tested for impact absorption.

How Much Play Bark Do I Need?

Use the calculator at the top of this page — set your depth to 200mm, 250mm or 300mm based on the table above. For a typical 4m × 3m play area at 300mm deep, you need 3,600 litres (3.6 cubic metres) — roughly 4 bulk bags. That is significantly more than a decorative border, so always calculate before ordering.

Play bark settles by approximately 20% in the first few months. Order 10–20% extra to account for this and top up annually to maintain the required safety depth.

Need to lay a lawn next to the play area? Our lawn seed calculator works out the right amount of seed, or try our turf calculator for instant results with turf rolls.

How Much Bark Do I Need? Coverage at Different Depths

Quick answer: 1,000 litres of bark mulch covers approximately 20m² at the standard 5cm depth, or 13m² at 7.5cm depth. At 5cm depth, you need 50 litres of bark per square metre. At 7.5cm depth, you need 75 litres per square metre.

The amount of mulch you need depends heavily on the depth you apply it. Here is a quick-reference table showing how much bark mulch covers at three common depths — 25mm (decorative top-up), 50mm (standard weed suppression), and 75mm (heavy-duty borders).

Bag counts based on 80-litre bags, rounded up. For exact figures, use the calculator above.

Play Bark vs Decorative Bark vs Standard Bark Mulch

Choosing the right bark type matters — play bark, decorative bark and standard bark mulch look similar but serve very different purposes. Here is how they compare. For bark chippings and play bark calculations, use our bark chippings calculator.

Key takeaway: Never use standard bark chippings in play areas — they can contain sharp splinters and are not tested for impact absorption. Always specify play-grade bark (BS EN 1177 compliant) for any area where children play.

UK Retailer Bark Bag Sizes — Wickes, B&Q & Amazon

Bag sizes vary between retailers, so knowing what each one stocks helps you order the right amount. Here are the most common bark bag sizes available at major UK garden centres and DIY stores.

Ordering tip: Always round up and order 10% extra. Bark compresses during transport and spreads less evenly than you expect — you do not want to run short halfway through a border.

When to Mulch Your Garden in the UK

Timing matters almost as much as depth. Mulching at the wrong time of year can trap cold soil, lock in weeds, or waste money on bark that washes away before it settles.

Best time: late March to early May

The ideal window for mulching in the UK is late March to early May — after the soil has warmed from winter but before summer dry spells begin. At this point, soil is moist and warm enough for plant roots to grow through mulch, and the mulch locks in that spring moisture for the rest of the growing season.

Second-best time: October to November

An autumn mulch insulates plant roots against frost and prevents winter rain from compacting bare soil. Apply after cutting back perennials but before the first hard frost. Autumn mulch also suppresses winter weeds that would otherwise establish before spring.

When NOT to mulch

Avoid mulching in June to August unless topping up an existing layer — bark applied to dry, sun-baked soil acts as a barrier that prevents light rain from reaching plant roots. Also avoid mulching frozen ground in winter, as the bark traps cold and delays spring soil warming.

Planning your spring mulching? Our March planting guide and April planting guide show what else to do in the garden alongside mulching.

How Much Does Bark Mulch Cost? UK Price Guide 2026

Bark mulch prices vary hugely depending on how you buy it. Here's what you'll pay at major UK retailers for standard bark mulch, so you can budget before ordering.

Money-saving tip: For areas over 15m², a bulk bag is almost always cheaper than individual bags — even with delivery. A 20m² border at 50mm deep needs 1,000 litres. That's 13 standard 80L bags at £5–£8 each (£65–£104) versus one bulk bag at £50–£80 delivered. Use the calculator above to get your exact volume, then check whether bags or bulk works out cheaper.

How Long Does Bark Mulch Last?

Bark mulch is not permanent — it breaks down over time, which is actually a benefit because it adds organic matter to your soil. Here's how long each type lasts before needing replacement.

To maintain a 50mm mulch depth, plan to add about 25mm of fresh bark each spring. Use the calculator above with 25mm as the depth to work out how much top-up material you need — it's roughly half the initial order. Spring top-ups in March or April are ideal, just before the weed germination season begins.

Best Bark Mulch UK 2026 — Our Top Picks

From budget bark mulch to premium composted bark, here are the best mulch products you can buy in the UK right now.

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