The Most Accurate Bark, Mulch & Wood Chip Calculator Online | How Much Do You Need?

Key Takeaways

• For mulching beds and borders, lay bark or wood chip 5 to 7.5 cm deep, which works out at roughly 13 to 20 m² per bulk bag (1,000L) depending on depth.
• For play areas, the depth depends on the equipment’s critical fall height (the maximum height a child could fall from), starting at 15 cm for low equipment and going up to 30 cm or more for anything above 2m.
• Bark and wood chip bag volumes are not standard, and our own range varies due to the space between bark and wood: builders bags are 600L on the bark products and 700L on the wood chip, bulk bags 1,000, XL 1,200 and jumbo 2,000. Compare litres not the bag names.
• Once you put your dimensions in, my calculator tells you honestly whether you are likely to have any left over or any shortfall.
• Bark and wood chip settles by 10 to 15% in the first few weeks as it compresses under its own weight, so I order 15% over the calculated figure as standard and 20% on a deep play surface.

I have lost count of how many times I have turned up to a job and found the client has ordered a bulk bag to many, or worse, a bag too few. One job comes to mind, where a customer had insisted on ordering the play bark for their kids ninth birthday party present. Disaster! Unfortunately, they under-ordered the amount needed for safety for a play area, by two bags! Due to national stock levels for the deluxe pine play nuggets, there was none available. The entire party arrived to a play gym that was dangerously thin on bark which stressed everyone involved and put a big dampner on the party for all the kids – not to mention the added costs! They had to wait four weeks for a second delivery.

Start with the product dropdown. Bag sizes vary by product, and picking yours means the calculator only ever recommends bags you can actually order. This calculator can save you from mistakes that can cost you financially and emotionally, but it only works if you know what depth you need.

How Deep Should Bark or Mulch Be?

The depth you need depends entirely on what you are using it for. Get this wrong and everything else follows: too shallow and you waste your time, too deep and you waste your money (or worse, damage your plants).

Mulching Beds and Borders

For weed suppression and moisture retention around plants, I lay between 5 cm and 7.5 cm. If the bed has never been mulched before, go with 7.5 cm. If you are topping up an existing layer, 5 cm will do. Go thinner than 5 cm and weeds push through within weeks. Go thicker than 10 cm and you risk the bark holding too much moisture against plant stems, which can cause collar rot (where the mulch sits permanently damp against the base of the plant, eventually rotting the stem). In my opinion, 7.5 cm is the sweet spot for most beds. It suppresses weeds properly, holds moisture through a dry spell, and breaks down slowly enough that you are not replacing it every season.

Pathways

For a bark or wood chip path that takes regular foot traffic, I would go 7.5 to 10 cm over a weed membrane. Anything less and you will see the fabric or soil showing through within a couple of months. I always use hardwood chips on paths rather than bark, because they compact more firmly underfoot and last longer before breaking down. For wood chip driveways (which take heavier use), 10 to 15 cm minimum over a proper compacted sub-base.

Chicken Runs

A chicken run wants 7.5 to 10cm of seasoned hardwood chip on ground that drains, which is roughly 75 litres per square metre at 7.5cm. Take it to the full 10cm where the ground sits wet, and treat 2 to 3cm as decorative: it treads into the soil and you are back to mud by the next rain.

Deep litter is the other setting entirely, 20 to 25cm of chip and other browns that the birds turn and compost in place over the year. Start that at 5cm and call it deep litter and you get the worst of both. Hardwood only in a run, because softwood slumps into a damp mat within a season and bark holds water by design. The type, the depth and the change-over routine are all in my wood chip for a chicken run guide.

Play Areas

Play areas are a different calculation entirely. The depth is dictated by the critical fall height of your equipment (the maximum height a child could fall from), and there are tested minimum depths for each material type. This is not guesswork. See the fall height table below, and always check against the BS EN 1177 standard if you are building anything for public or commercial use.

Critical Fall Height Safety Depths

Compare the highest point of your play equipment against the material type below to find the minimum uncompressed depth you need. For home installations, I would add at least 5 cm on top of the table minimum as a safety margin, because bark compresses over time.

Material	15 cm / 6 in depth	23 cm / 9 in depth	30 cm / 12 in depth
Play chip	2 m / 7 ft	3 m / 10 ft	3.3 m / 11 ft
Play bark	1.8 m / 6 ft	3 m / 10 ft	3.3 m / 11 ft
Engineered wood fibre	1.8 m / 6 ft	2 m / 7 ft	3.6 m / 12 ft
Fine sand	1.5 m / 5 ft	1.5 m / 5 ft	2.7 m / 9 ft
Coarse sand	1.5 m / 5 ft	1.5 m / 5 ft	1.8 m / 6 ft
Play gravel	1.8 m / 6 ft	2 m / 7 ft	3 m / 10 ft
Medium gravel	1.5 m / 5 ft	1.5 m / 5 ft	1.8 m / 6 ft

Source: The Handbook For Playground Safety. Depths are for uncompressed material.

How Much Does a Bag of Bark Cover?

This is the question I get asked more than any other, and the answer depends entirely on which bag you are buying. Our range runs to five bag sizes, and the builders bag is different between the products due to the shapes: 600L on the bark, 700L on the wood chip. Here is what each one covers at the depths people actually use, before any settlement allowance:

A 4m x 6m flower bed at 7.5cm is 24 m², which is 1,800 litres. On a bark product that is 3 builders bags or a single jumbo bag with a little spare. On a wood chip product it is 2 bulk bags, or 30 of the 70 litre sacks if the only way in is through a side gate. The calculator does this for you, and the table is here just for a sanity check before you order.

How to Measure Your Area

Grab a tape measure and work in metres. For a rectangular bed, it is length times width. For an L-shaped border, split it into two rectangles, measure each one separately, and add the totals together. For a circular tree pit or round bed, measure the diameter (the distance across the widest point), halve it to get the radius, then multiply: 3.14 x radius x radius.

One thing I always do: measure at three different points across the area and use the largest number. Garden beds are rarely perfectly even, and it is far better to have half a wheelbarrow of leftover bark than a bare patch showing in the corner.

Tips for Getting Your Order Right

Add 10% for settlement

Fresh bark settles by roughly 10 to 15% in the first 2 to 4 weeks. If you order exactly what the calculator says and nothing more, you will end up with visible thin spots. I round up by 10-20% on every job, and my clients have never regretted it.

Check your access before ordering

Bulk and jumbo bags arrive on a lorry - usually on a pallet - and the driver drops them as close to the kerbside as possible. If your garden is at the back of the house with a narrow side gate, you will need to barrow the bark in by hand. I have seen people order 4 bulk bags for a back garden only to spend an entire weekend running a wheelbarrow through a 70 cm gate. If access is especially tight, ordering in builders bags rather than bulk or jumbo bags means smaller loads to barrow through, even though it usually works out slightly more expensive per litre. For tight-access situations, loose fill delivery by tipper truck is sometimes more practical if your supplier offers it, or smaller bagged products you can carry through by hand.

Topping up vs. starting fresh

If you are refreshing an existing mulch layer, you usually only need 2 to 3 cm on top, not the full 7.5 cm again. Rake out any badly compacted or visibly decomposed material first so the new layer sits properly and does not just slide off. Most bark mulch lasts 2 to 3 years before it breaks down enough to need topping up, but high-traffic areas and exposed windy sites will need it sooner.

Next Steps

Once you have your measurements and depth sorted, the calculator does the rest. If you need help choosing which type of bark or woodchip is right for your project, the material comparison guides and bark buying guides on the site cover the differences between decorative bark, play bark, and wood chips in detail.

FAQs

How much bark do I need for 10 m²?

At a standard mulching depth of 5 cm, you need 0.5 m³ (500 litres), which is just under a bulk bag or roughly one builders bag. At 7.5 cm, you need 0.75 m³, so a single bulk bag will do with a bit to spare. For a play surface at 30 cm, you would need 3 m³, which is 3 bulk bags or a bulk bag plus a jumbo bag.

What area does 100 litres of bark cover?

At 5 cm deep, 100 litres covers 2 m². At 7.5 cm deep, it covers roughly 1.3 m². The shallower you go, the further it stretches, but there is a minimum below which it stops suppressing weeds effectively.

How much does 1 cubic metre of bark weigh?

Between 250 and 350 kg depending on the type and moisture content. Play-grade bark chip tends to be lighter (closer to 250 kg per m³) while decorative bark mulch with larger, denser nuggets sits closer to 350 kg per m³. A bulk bag is roughly 1 m³.

How deep should bark be to stop weeds?

A minimum of 5 cm, ideally 7.5 cm. Below 5 cm, weeds push through within weeks. Pair the bark with a weed membrane underneath for the most effective suppression, and you will get a good 2 to 3 years before any serious breakthrough.

How many bulk bags of bark do I need?

One bulk bag holds 1,000 litres and covers about 20 m² at 5cm deep, or 13 m² at 7.5cm. A builders bag covers 12 m² at 5cm on our bark and 14 m² on our wood chip, because the two are packed at 600 and 700 litres. Work in litres rather than bag names, then use the calculator at the top of this page for your own measurements.

Does bark compress after you lay it?

Yes. Fresh bark settles by roughly 10 to 15% in the first 2 to 4 weeks. I always tell people to order 10% more than the calculator suggests, and to avoid walking on freshly laid play bark for a few days so it settles evenly rather than getting trodden into dips and high spots.